Water Heating and Data Collection

A joint initiative of Australian, State and Territory and New Zealand Governments.

Water Heating Data Collection and Analysis

Residential End Use Monitoring Program (REMP)

April 2012

REMP Water Heating Data Collection and Analysis 2

Commonwealth of Australia 2012

This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Commonwealth.

Requests and inquiries concerning reproduction and rights should be addressed to the:

Commonwealth Copyright Administration Attorney Generals Department

Robert Garran Offices, National Circuit Barton ACT 2600

or posted at:

http://www.ag.gov.au/cca

This Report is available at

www.energyrating.gov.au

While reasonable efforts have been made to ensure that the contents of this publication are factually correct, E3 does not accept responsibility for the accuracy or completeness of the content, and shall not be liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the contents of this publication.


CONTENTS 3

EXECUTIVE SUMMARY 5

1 INTRODUCTION 71.1 Scope of End-use Why it is Important 71.2 Policy Background 8

2 WHAT DO WE KNOW ABOUT WATER HEATING? 102.1 Sales and Ownership 102.2 Use 102.3 Technology 122.4 User Behaviour 122.5 Energy and Efficiency 13

3 KEY ISSUES FOR END-USE MONITORING OF HOT WATER 153.1 Electric Storage Off Peak 153.2 Electric Storage Continuous 153.3 Gas Storage 153.4 Gas Instantaneous 163.5 Solar Boosted Systems 163.6 Heat Pump Systems 163.7 Water Temperatures 173.8 Hot Water Energy Delivery 17

4 STRATEGY FOR QUANTIFYING HOT WATER ENERGY 194.1 Element 1: High level survey (social and physical) combined with billing data (where available for separately metered systems) 194.2 Element 2: Detailed hot water end use metering 204.3 Element 3: Monitoring energy consumption of water heaters 204.4 Additional Macro Data 21

5 KEY ISSUES TO CONSIDER WHEN MEASURING HOT WATER 22

6 LESSONS FROM THE PILOT 23

7 REFERENCES 28

APPENDIX 1 FURTHER PILOT STUDY DATA 30

Contents


Figures Figure 1: Trends in hot water energy consumption, Australia ......................................................................................8Figure 2: Distribution of Y8 water heater annual energy Victoria 1990 ................................................................... 11Figure 3: Distribution of Individual Hot Water Events House 1..............................................................................24Figure 4: Distribution of Hot Water Event Duration House 2 (6 months data)...................................................... 25Figure 5: Relative Hot Water Usage by Month 5 REMP homes............................................................................... 27Figure 7: Total Energy Consumption 5 REMP homes..............................................................................................30Figure 8: Monthly Electricity and Gas REMP House 1............................................................................................. 31Figure 9: Monthly Electricity and Gas REMP House 2 ............................................................................................ 31Figure 10: Monthly Electricity and Gas REMP House 3 ..........................................................................................32Figure 11: Monthly Electricity and Gas REMP House 4 ...........................................................................................32Figure 12: Monthly Electricity and Gas REMP House 5........................................................................................... 33Figure 13: Daily Hot Water Consumption REMP House 1 ..........................................................................................34Figure 14: Daily Hot Water Consumption REMP House 2..........................................................................................34Figure 15: Daily Hot Water Consumption REMP House 4.......................................................................................... 35Figure 16: Time of Day Gas Consumption for REMP House 4.................................................................................... 35Figure 17: Hot Water Use by Time of Day REMP House 1 .......................................................................................36Figure 18: Hot Water Use by Time of Day REMP House 2 ......................................................................................36Figure 19: Hot Water Use by Time of Day REMP House 3 ...................................................................................... 37Figure 20: Hot Water Use by Time of Day REMP House 4...................................................................................... 37Figure 21: Hot Water Use by Time of Day REMP House 5 ......................................................................................38Figure 22: Hot Water Event Volume Distribution REMP House 1 ..........................................................................39Figure 23: Hot Water Litres Per Day Distribution REMP House 1..........................................................................39Figure 24: Hot Water Starts Per Day Distribution REMP House 1..........................................................................40

Tables Table 1: Key Characteristics of Hot Water Consumption 5 REMP Homes ..............................................................23


This paper is one in a series of papers on end-use metering methodologies, prepared to assist in the development of end-use metering campaigns. The full suite of papers are:

Residential End Use Monitoring Program (REMP) General Introduction and Overview; Residential End Use Monitoring Program (REMP) Water Heating Data Collection and Analysis; (this paper) Residential End Use Monitoring Program (REMP) Lighting Data Collection and Analysis; Residential End Use Monitoring Program (REMP) Heating and Cooling Loads Data Collection and Analysis; Residential End Use Monitoring Program (REMP) General Plug Loads Data Collection and Analysis; Residential End Use Monitoring Program (REMP) Equipment Recommendations; Residential End Use Monitoring Program (REMP) Data Management Strategy: Data Handling and Database

Requirements/Specifications.

Each of those papers contains recommendations that are specific to those end uses or elements. This paper contains general information and recommendations that are applicable to hot water.

The Australian Government is considering end-use metering campaigns to fill various gaps in its knowledge, especially relating the important residential end-uses. These papers will be used to set out requirements for a possible future tender.

Water heating is the second largest energy end use in the Australian residential sector (after space heating), accounting for about 90 PJ of energy consumption in 2008, which is about 23% of total residential energy consumption.

A good understanding of the demographic and technical factors that drive hot water use will enable:

More reliable projections of household demand for hot water; A better understanding of the interaction between the total hot water demand, drawoff patterns, and heat losses,

in the water heater and in the pipework; An understanding of the energy required to supply the hot water via various water heater types; Greater confidence in the development of policies to reduce water use in general and hot water consumption in

particular; Greater confidence in the development of policies to reduce water heater energy use and related greenhouse gas

emissions; Evaluation of programs to reduce hot water energy consumption; Better consumer advice on system selection and use; Better advice to consumers on plumbing layouts, water fitting selection and use.

A range of factors are thought to affect hot water consumption including:

Number and age of occupants; Number, frequency and duration of use of fittings (eg showers, baths, taps); Number, connections (hot/cold), self-heating capability, frequency of use and cycles, and temperature

preferences for clothes washers and dishwashers; Number and type of water heaters installed; Layout of the pipe work in the home and the lagging.

For this paper, the following terms are used:

water heater: water heater (up to the point of discharge into the hot water system) hot water system: combination of the water heater and the hot water pipework appliances: clothes washers, dishwashers and other automated devices that may draw hot water from the hot

water system end use fittings: showers, taps, mixer valves, etc., operated directly by users plumbing fittings: mixer valves, pressure reductions valves that may be installed in the hot water system.

Executive summary


The metered energy consumption of a water heater is a function of the water heater characteristics (energy efficiency and losses), the hot water system (plumbing layout and losses), user interaction from end use fittings or appliances (hot water draw off volumes and timing) and to a lesser extent, the ambient conditions during operation (small effects from changes in air temperature and cold water supply temperature; large effects where the water heater collects ambient energy, such as solar thermal or heat pump).

The objective of end use measurement campaigns should be to disaggregate the key factors that affect energy consumption in a way that allows the influence of the appliance, its installation and its use to be characterised and separately quantified in a generic fashion. This means that the influence of the water heater characteristics (efficiency and performance), ambient conditions and user interaction (hot water demand) need to be separately examined. For water heaters, hot water demand is the largest and most important influence on water heater energy consumption and is the most poorly documented element, with very few studies recording this parameter. A good deal of engineering and modelling data exists: this enables the input energy consumption of various water heater types to be estimated with reasonable accuracy once a hot water delivery profile is assumed.

If the key variables contributing to hot water demand are identified, the relevant data are collected and analysed correctly, it should be possible to estimate the actual energy consumption of any known water heater which is installed in any household, which is a key requirement for policy evaluation.

The following data strategy would improve knowledge of hot water use and water heating energy consumption:

High level survey (social and physical) to determine key missing attributes related to water heating (eg water heaters used, characteristics of the hot water system, appliances, end use fittings, demographic factors, usage factors);

Quantification of hot water usage profiles (volume, temperature, end use and time) for a significant number of homes;

Measurement of energy input of water heaters together with hot water usage profiles in a limited number of homes.

This paper contains a brief discussion on the lessons learnt from the REMP pilot project is outlined in this paper as well as an overview of some of the hot water related data captured by this project.


This paper is one of a series of papers on energy end use measurement that have been prepared for the Department of Climate Change and Energy Efficiency (DCCEE).

This paper provides general information on the operation of different types of hot water systems and examines data collection strategies that can maximise the information on hot water usage and system performance during normal use. The purpose of this paper is to examine issues surrounding the in situ measurement of hot water energy consumption installed and used in homes, and to provide guidance on the parameters that should be monitored as part of an end use measurement program, in order to obtain a clearer understanding of the nature of hot water energy use and the energy implications for different types of water heaters, hot water systems, appliances that use hot water and end use fittings.

The main purpose of data collection should be to:

Identify the main drivers of household hot water demand and hot water energy consumption; Ensure that the hot water demand and drawoff assumptions used in the simulation or testing of the

performance of water heaters are reflective of actual use (so that the relative energy consumption of different water heaters can be fairly compared);

Support the development and evaluation of policy measures to reduce energy consumption and emissions associated with water heating1.

1.1 Scope of End-use Why it is Important Water heating is the single largest energy end use in the Australian residential sector, accounting for about 90 PJ of energy consumption in 2008, which is about 23% of total residential energy consumption (DEWHA, 2008).

Historically, electric storage systems have dominated, but their share of the stock is now in decline. Figure 1 shows the estimated trend in energy consumption by water heater type. The ownership by type of water heater is highly variable at a state level and to some extent is influenced by climate and availability of different fuel sources. It is also influenced by regulations and by cash rebates for the installation of particular types of water heaters, notably solar-assisted and heat pump types.

1 For example, one finding from the REMP pilot homes was that there are a large number of small hot water drawoffs in most homes. A technological solution to this issue is worthy of investigation.

1 Introduction


Figure 1: Trends in hot water energy consumption, Australia

Source: DEWHA (2008)

The main trends that are evident are a decrease in electric storage energy (resulting from a decline in penetration and also from reduced heat losses after the introduction of Mandatory Energy Performance Standards (MEPS) in 1999), a gradual increase in the ownership of gas systems (which is limited by the extent of the gas distribution network) and some increase in solar water heaters, especially since 2005 when a number of state and federal policies came into force. There are also likely to be some declines in hot water use per house arising from the increasing prevalence of water-efficient appliances (low flow shower head and more efficient clothes washers, or clothes washers that heat water internally) and fewer people per household2. While there is some data on hot water usage by end use, data on trends in total hot water consumption are neither well understood nor documented with firm data.

1.2 Policy Background A complex array of state policies and energy prices is influencing the selection of water heater type in new dwellings, and some states are looking to also influence replacement of water heaters. These policies are outlined by Wilkenfeld (GWA, 2010), and are mainly intended to influence the take up of water heater technologies that have a lower greenhouse intensity. The criteria for each policy vary at a state level, as there are many local influences and factors such as climate (solar water heaters) and the availability of mains gas.

The quantity of hot water used in the home is the key driver for energy consumption by water heaters. The objective is to be able to characterise hot water usage of monitored homes in a way that will enable a more general

2 Fewer people per household will reduce hot water consumption per house, but total energy will probably increase due to the fixed energy losses associated with supplying each household.


model of hot water use to be developed3. A good understanding of the demographic and technical factors that drive hot water use will enable:

More reliable projections of household demand for hot water; A better understanding of the interaction between the total hot water demand, drawoff patterns and heat losses; The energy required to supply the hot water via various water heater types; Greater confidence in the development of policies to reduce water use in general and hot water consumption in

particular; Greater confidence in the development of policies to reduce water heater energy use and their related

greenhouse gas emissions; Evaluation of programs to reduce hot water energy consumption; Provision of better consumer advice on system selection and use.

3 The current data used to determine energy consumption under AS/NZS4234 (for example) is extremely limited and relatively old. Initial data from REMP monitoring shows that actual hot water use is highly variable and not very seasonal, which is likely to affect the comparative performance of many systems.


The factors known to affect hot water consumption are briefly discussed below. However, it should be noted that the amount of quantitative data available from end use metering programs is still relatively small. The relationships documented below are either based on technical knowledge of the system operation (from laboratory data) or are hypotheses that need to be confirmed through end use metering.

2.1 Sales and Ownership Sales: Data on sales are fairly poor. The Australian Bureau of Statistics (ABS) publishes some manufacturing and import data, but this is not easy to access or interpret. The market research company, BIS Shrapnel, used to analyse and report ABS time series data in their biennial report on appliances, but now they only estimate current market (see BIS 2008). Sales data are national and there is data for largest 5 states for some types of water heaters. Rapid changes in market trends make sales estimates difficult to track. Unlike, other domestic whitegoods, hot water sales at model level are not available through GfK retail sales tracking as most sales are not through traditional appliance retail outlets. Almost no data is available about the sales weighted share of attributes within types (eg size distribution). Information on installation of water heating systems in new homes in each state is generally available through approval data from regulatory authorities or through state based surveys (eg see BASIX 2008 analysis), although the coverage and format of this data is quite variable.

Ownership: ABS has a reasonably comprehensive coverage of ownership of water heater types in the ABS4602 series, which is currently undertaken every three years. ABS records all energy sources; such that they are not mutually exclusive in terms of type4 (eg solar electric systems are recorded as solar and electric). Additional internal analysis by ABS (beyond the data included in the ABS4602 publication) on the survey data has provided cross tabs (to the extent that this is available) on some parameters for type of water heater by variables such as household size, available fuels and house type. Some state data is also available through ABS State surveys (eg SA, NSW and WA) and ownership surveys conducted by BIS Shrapnel as part of the appliance market report (BIS 2008).

2.2 Use Hot Water Use: Hot water consumption is the biggest single factor that effects the energy consumption of a hot water system. Very little direct or indirect data are available for hot water use, and what little there is now obsolete:

A study in Victoria in the 1980s measured hot water use in 14 homes (Guthrie and Kimpton, 1987); Some early studies in the 1970s measured hot water use in 64 flats in Melbourne with instantaneous water

heaters in 64 flats in Melbourne (SECV 1971); BRANZ have quite a deal of hot water heater end use measurement data for NZ over the past 10 years as part of

their HEEP project (BRANZ 2007) for a wide range of water heater types. However, the NZ water heater market has a number of significant differences to Australia so few conclusions can be drawn from this data; for example NZ has a very limited natural gas distribution network, a much higher prevalence of low pressure electric systems and significantly colder climatic conditions.

Energy End Use Data: Little energy end use data for water heaters is available.

The then NSW electricity wholesaler, Pacific Power, measured the electrical energy consumption of around 250 electric water heaters in 1994 (Pacific Power, 1995). Hot water consumption can be estimated from this data (assuming close to 100% energy conversion and taking into account heat losses5). However, the prevalence of off peak units in the sample complicates the analysis).

4 The way the ABS survey is structured does not capture information on multiple water heaters per household, whether multiple fuels used in each water heater or the primary energy source. Many respondents do not know what sort of water heater they have. 5 Heat losses for off peak systems cannot be accurately estimated without knowledge of the drawoff profile and tank storage temperature, which cannot be determined from off peak energy input data alone.

2 What do we Know About Water Heating?


Some retailer utility billing data for off peak tariffs was available in the 1990s but since the privatisation and corporatisation of energy retailing in most states, such data sources have become difficult to access because there is:

Less consistent classification of users by tariff (over 100 electricity retailers operate in some states); Much less public information on energy by tariff with increasing corporatisation and privatisation of electricity

utilities and competitive retail markets; An increasing prevalence of other devices attached to off peak circuits; A move to time of use tariffs, where all off peak usage is pooled, which means separate tracking of water heating

through separate off peak metering is no longer recorded.

Despite the historical problems with top down data, some state agencies are having success in assembling regional level utility data for detailed analysis of energy consumption and trends.

Almost no gas water heaters have been metered in situ in the public domain. Some data were collected by the Gas & Fuel corporation in the 1970s but it is believed that this data have been lost. Gas utilities often prepare estimates of gas consumption for water heating as part of their pricing proposals to the Australian Energy Regulator.

Distribution Variability of Hot Water Use: There is some information on average hot water energy consumption per home (mainly through separate metering for off peak electric systems). This data indicates a wide distribution in hot water consumption per household, as indicated by the following figure. This data suggests that there is a wide variation in hot water use from household to household, but other explanatory data is not available.

Figure 2: Distribution of Y8 water heater annual energy Victoria 1990

Source: SECV billing database, 1990

Some data are known about time of hot water use, but this is very limited (see EES 2004 for details).


2.3 Technology Characteristics of New Water Heaters:

The performance of electric storage water heaters is relatively predictable. They are regulated for MEPS, so design heat loss levels are known according to the size of the tank and the age. There is little public data about sales of each by size, but as there are relatively few manufacturers, this information could be requested from the suppliers.

Some data is available on the performance of each model of gas water heaters through the AGA labelling scheme (although critical data such as maintenance rate, startup energy and burner efficiency are not accessible). Gas water heaters are in the process of being regulated so this data may become more accessible in due course. Again, model market shares are more difficult to obtain.

Most solar and heat pump water heaters are rated for The Small-scale Technology Certificates (STCs - previously RECs under MRET), but these are not necessarily good predictors of actual performance on their own. The underlying modelling data used to generate STC numbers are very complicated and very difficult to access. Sales by model are not known.

The physical plumbing layout of the hot water system, fixtures and fittings are also significant. Major factors include the presence of water saving devices (eg low flow shower heads) and whether clothes washers and dishwashers are connected to the hot supply. Pipe layouts, the flow rates of each fitting and frequency of drawoffs all influence hot water use. For a given flow rate, the longer the pipe run, the longer the time that shower and tap users have to wait for water at the required temperature, and hence the greater the tendency to run sub-temperature water to waste. Energy is wasted in the rejected water, and also lost from the pipe after the draw ends (unless there is another draw almost immediately).

The orientation of collector panels will influence the performance of solar water heaters, and exposed locations can influence the heat loss of storage tanks, whatever the energy type. The prevalence of mixer taps can mean frequent small drawoffs of hot water (many not perceived by the user) unless the design is set to a default 100% cold position6.

2.4 User Behaviour Clearly, a range of demographic factors will affect hot water consumption. Household size is an important factor as is the age of household members (anecdotally the presence of teenagers is associated with longer average shower times, and young children with frequency of bathtub use and more clothes washing loads). There may also be household income effects.

The behaviour of household members interacts with the physical layout of the hot water system, eg via showering frequency, flow rates and duration, the frequency of clothes washer and dishwasher use and preferred washing temperatures, cycles and water level settings.

There are also likely to be some secondary demographic and geographical influences on selection of hot water system: households that have gas available are more likely to have gas water heaters (houses without natural gas are less likely to use LPG for hot water), large households will tend to have larger hot water systems (eg large electric storage, large capacity gas where available), rental houses will tend to have low purchase cost systems that may have high operating costs (eg small electric or other conventional systems). Apartments will usually be quite restricted in the choice of water heater (as a rule solar is usually not possible, gas can be difficult, limited space for electric storage systems). Dwellings in hotter, sunnier climates may have a higher prevalence of solar water heating.

The type of water heater could, to some extent, influence the usage and subsequent energy consumption patterns of the household. For example, off-peak electric systems are limited by the storage capacity (unless there is an upper boost element, where there is day-time top-up or the heating hours are extended, as with T33 and OP2) so some households may ration their hot water use by experience to minimise the possibility of running out (they

6 Data from the REMP pilot appeared to indicate that very small hot water events (less than 2 litres) made up as much as 20% of all hot water consumption. While this is to be further investigated, it would appear that mixer taps may be responsible for much of this wasted energy.


would learn this behaviour by trial and error). Small electric storage systems have limited short-term capacity and response time and where this causes a constraint, households may learn to limit peak use of hot water within the recovery period (eg may encourage spacing of showers). Low pressure electric storage systems have limited flow rate and practically limit hot water energy consumption through a low energy delivery rate. Long start-up times for instantaneous gas water heaters, or long pipe runs for any type of water heater, may discourage the use of hot water for small tasks. Relatively unlimited energy supply from gas systems is unlikely to constrain total hot water use (which may manifest itself as very high hot water consumption in some homes).

2.5 Energy and Efficiency Clearly, total hot water use (energy) is the key factor that drives energy consumption of water heaters. The energy consumption of water heaters is the sum of the thermal energy added to the hot water at the exit of the water heater (relative to the thermal energy contained in water at the inlet), plus standing heat losses for storage types, plus the losses in converting the energy supplied to the thermal energy in the water, plus start-up losses plus control and fan energy (for instantaneous gas), as well as pumping energy (for some solar configurations). Some of the thermal energy transferred to the water is lost from pipes during and after drawoffs, and the balance is contained in the hot water drawn off at the supply points. In most hot water systems, the hot is mixed with the cold to achieve a high temperature at the supply point the lower the cold water mix temperature, the greater the hot water volume required to achieve the target temperature.

Finally, some of the thermal energy in the drawoff water may be wasted.

There is some measured data of hot water usage patterns throughout the day (see EES 2004), although this is very limited and relatively old. The overall pattern of use (MJ delivered by hour) is not terribly important for gas storage or continuous (small) electric storage. Time of use has some impact on total energy consumption of large off peak storage units (with a limited duration overnight energisation profile). If most of the water is used in the morning, the storage temperature in the tank falls, and the overall heat loss is lower than if most hot water is used in the evening, but the effect is fairly small of the order of 10% to 20% of heat losses, which may themselves be only 15-30% of total energy use.

The interaction of time of use and energisation profile is important for electric-boosted solar water heaters. If the main hot water loads are in the evening and boosting is under restricted Off Peak (OP) tariffs, then electricity use may be high, whereas if the main hot water loads occur in the morning, the solar contribution to reheating will be much higher. OP1 (restricted time tariff) solar systems are now fairly unusual as they perform poorly under the Small-scale Technology Certificates (low solar contribution). For all electric systems that have limited periods of boosting (eg off peak systems) it is important to note that hot water usage and the time of reheating will be separated in time, which means that data usually needs to be aggregated into boost periods for analysis purposes.

The most critical data gaps are:

Total hot water consumption; Variation from day to day; The pattern of hot water use events (ie the time of commencement and the duration and volume of each

drawoff).

The spacing of events is also important for instantaneous gas hot water systems because of the impact of start-up losses7. The number of draw-off events has little overall effect on the task efficiency of other water heater types. However, plumbing losses through heating and cooling of hot water in the hot water system affects all systems. Firstly, when hot water is required, the (cool) water in the pipe has to be expelled and replaced with hot water to the point where it is required. This flowing hot water has to heat the pipe to an equilibrium temperature. While hot water is flowing, there will also be some small heat losses from the pipe (depending on the flow rate, thermal insulation around the pipe and temperature difference the temperature at the point of supply will always be less than the water heater outlet). Finally, when hot water demand ceases, the hot water left in the pipe slowly cools down to ambient temperature (this may not cool completely if more hot water is required in the short term). So the key factors to assess hot water system (plumbing distribution) efficiency are length and diameter of pipe runs as

7 For instantaneous gas systems with no storage, there is some delay between the time the hot water tap is turned on until hot water is delivered. A certain amount of energy is required to start the burner and increase the temperature of the heat exchanger and other fittings to the hot water delivery temperature. This initial energy requirement (in order to get hot water) is called start up loss (may be 0.2 to 0,4 MJ), while unheated water is term wasted water (although the water may or may not be wasted, depending on the application) (may be up to a few litres).


well as the frequency (spacing) and duration of hot water events. These attributes are not well known and this type of data is an important complement to information about the water heater.

Efficiency of plumbing distribution is a house design issue. Reducing distribution losses in existing homes is difficult and expensive, if possible at all. However, the information gained from monitoring can help frame design rules for new construction as well as the value of retrofits (such as pipe lagging). There may be interactions of plumbing losses with water heater type in that some types lend themselves to greater flexibility in location, and can be sited nearer the main drawoff points. Instantaneous water heaters are usually associated with additional energy losses because the water that does not reach the target supply temperature during startup, may also be wasted (unless it is used for a volumetric purpose, such as filling a bath).

For electric systems, typical total annual energy consumption is in the range 2,000 kWh/year to 5,000 kWh/year and heat losses are of the order of 300 kWh/year to 1,000 kWh/year (since MEPS came into effect in 1999 we can assume that there are very few pre-MEPS units left in operation.

For gas storage water heaters, energy consumption typically ranges from 10 GJ/year to 40 GJ/year. Heat losses will be of the order of 4 GJ/year to 8 GJ/year. Conversion efficiency is typically in the range 75% to 90% (theoretically). So hot water usage constitutes 60% to 80% of the total energy consumption. Smaller hot water loads have a higher proportion of losses.

For gas instantaneous water heaters, the energy consumption is estimated to be of a similar order to gas storage (should be less for more typical hot water deliveries). However, there is some limited anecdotal evidence that on average instantaneous gas water heater users have higher hot water consumption than gas storage systems. It is unclear why this may be the case (if it is in fact true) it may be driven by demographics (prevalence in larger householders, newer homes) and/or the lack of constraints on hot water delivery. Instantaneous systems do not have storage losses, but there is a start-up loss of the order of 0.2 to 0.5 MJ per start (depends on the interval between starts). Conversion efficiency is typically slightly lower in the range 75% to 80%, although some new systems are now in the condensing range8 (>85%). So hot water usage constitutes 70% to 85% of the total energy consumption, but the overall task efficiency is quite sensitive to the actual number of starts per day (fewer large hot water events can be more efficiently delivered than a larger number of small events). The gas water heater standard AS4552 (used as the basis for the AGA labelling scheme) assumes 19 starts per day, but the origin of this specification uncertain and its is unclear how representative this is today9. If the number of starts changes in proportion to hot water load, then instantaneous systems will deliver roughly consistent overall efficiency for small to large hot water loads. In contrast, overall task efficiency of storage systems declines with declining total hot water use.

8 High efficiency heat exchangers usually have a larger thermal mass and therefore higher start up losses. 9 Collection of this type of data would in fact be a key objective of an expanded REMP monitoring program. The impact of mixer taps would be an important element in understanding this data.


Hot water consumption presents some special problems in terms of end-use metering. Monitoring of the input energy consumption alone does not necessarily provide an accurate picture of the pattern of hot water consumption, without information on the characteristics and performance of the individual water heater that is being monitored. Even then, some parameters can only be estimated indirectly. Key issues by water heater type10 are set out below.

3.1 Electric Storage Off Peak Large electric storage systems generally operate on off peak tariffs (generally overnight boosting, some with extended hours) which means that energy consumption and hot water use are usually quite disconnected. Energy losses depend to some degree on daily usage profile (morning/evening) and the quantity of hot water used (lower draw-off will result in higher total losses). No data other than daily energy can be ascertained from energy metering data (hot water usage can be roughly implied/estimated). All electric storage systems are hardwired (separate circuit) and have to be metered at the switchboard, many have two elements (bottom and top the top element is often designed to operate only when the stored hot water runs out, the top element may be separately metered as general supply (so the off-peak meter may understate the total energy use), or in some utilities it is metered at the off peak rate; there may be one or two circuits at the switchboard, so the configuration needs to be carefully documented. The tariff used may also affect how the system is wired and controlled (many utilities use ripple controls to turn these circuits on and off so energisation profiles may vary day to day). These systems tend to be installed in larger homes and owner occupied homes.

3.2 Electric Storage Continuous Small electric storage systems tend to operate on continuous tariffs which means that energy consumption roughly tracks hot water use (with a small delay). Monitoring energy use can provide quite a good estimate of both hot water use and heat losses (heat losses can be estimated from overnight consumption when there is usually no load) when data is recoded for an extended period. As the element control is on/off and the input power quite high, hot water patterns from these data have to be estimated over a longer period (time of use over several months). All systems are hardwired (separate circuit) but not separately metered, and to monitor their energy use a metering system would have to be installed at the switchboard. Small systems that operated on controlled tariffs with extended boost hours need to be treated as off peak systems in terms of data collection and analysis. These tend to be installed in smaller homes, flats and rental houses.

3.3 Gas Storage Gas storage systems mask the actual hot water usage profile to some extent, although this is not really critical: the thermostat typically only responds when 5% to 10% of the storage capacity is drawn off (5 to 20 litres). Maintenance recovery cycles with no load are usually evenly spaced (but often with very long periods between recovery cycles), and these become more random and frequent when intermingled with hot water usage and recovery. So determination of time of day hot water profiles from gas water heater energy has to be done over a long period (of the order of months). Most gas storage water heaters have a constant gas burner rate and almost none have electrical connections, so metering of gas consumption is the only real option to determine energy input.

10 Boiling water units are treated as a electric storage water heater.

3 Key Issues for End-Use Monitoring of Hot Water


3.4 Gas Instantaneous Gas consumption by instantaneous water heaters tracks actual hot water use very closely as there is no storage of hot water. Each start-up is subject to some energy losses (associated with starting the burner and heating the combustion chamber and heat exchanger before any useful hot water is delivered11). So for these types of water heaters, the number of starts is critical in the determination of the energy consumption in the home. The number of starts is an area where there is very poor data. Given that the flow rate and temperature rise both determine hot water energy consumption, the volume and temperature of hot water for each event is also critical for these water heater types. A majority of newer instantaneous gas water heaters now have electrical connections, so this provides a low cost method to monitor the number of starts for a larger sample (and should always be measured where present, as this can account for significant energy). Metering of gas consumption (with electricity where applicable) is the only real option to determine energy input.

3.5 Solar Boosted Systems Solar systems have a range of possible configurations; flat plate or evacuated tube collectors which themselves can be thermosiphon or pumped water circulation. The electric or gas boosting may be in the storage tank (or outside the tank but in line (usually via a gas instantaneous water heater). The solar energy inputs cannot be readily tracked or directly metered. Metering of purchased (boost) energy only provides limited information on the system operation.

If all the physical parameters of the system are known, in some cases it may be possible to infer solar input from measurement of purchased energy and of the heat content of the hot water drawn off, and the solar radiation at the panel, using the TRNSYS simulation model. However, this would be very approximate and it would be difficult to account for large hourly and daily variations in input energy. A preferred approach is to measure actual ambient temperature and solar inputs and use actual hot water use as the basis for an analysis for the system operation and performance.

In the case of pumped systems, a plug in data logger could be used to track pump operation, but this would really need to be used in conjunction with global solar radiation measurements at the panel and information about thermostat set points to provide some meaningful data12. To more accurately assess performance, it is preferable to collect data on internal tank temperatures. Electric resistive boost energy is straight forward to measure at the switchboard, but data would be need on the element configuration and boost regime. In tank gas boosting can only be tracked using gas consumption metering (noting that maintenance losses are likely to be high for these systems). In line gas boost systems could possibly be successfully tracked using a plug in data logger on the gas boost system to track approximate boost energy if data was known about the boost heater (without the need for gas metering as these systems tend to have a fixed outlet temperature). In all cases, solar systems should have their hot water consumption measured in parallel to the measurement of input energy to have any hope of assessing system performance in the field. The highly variable nature of ambient inputs into these types of systems means that longer monitoring periods are required. Solar inputs are highly seasonal in nature and highly variable from day to day, which has to be considered along with the variability of hot water usage during analysis.

3.6 Heat Pump Systems The electricity consumption of heat pump water heaters can be readily measured using a plug in data logger as most systems use a standard single phase plug. Together with external ambient temperature data, sufficient data could be obtained to examine approximate overall system performance. The size and frequency of drawoff may impact on the efficiency of the system (recovery from deep drawoffs will be more efficiency than shallow drawoffs), so the hot water consumption profile should always be measured. Special attention needs to identify the operation of any boost element in the tank (either separately metered or through a distinctive power signature) or the operation of defrosting cycles in very cold ambient conditions (remove ice from the evaporator).

11 There may be reduced start up losses when hot water events are closely spaced as the water heater components may still be warm. 12 An alternative approach would be to measure volume of pumped flow to the solar panel and the inlet and outlet temperature to estimate energy delivery. The complexity of accurately measuring the performance of solar systems in the fields should not be underestimated.


3.7 Water Temperatures Hot water energy is always calculated using the cold water temperature as a base. Cold water supply temperatures vary throughout the year. Some water supply authorities monitor the temperature of water sent out from the main storages. There can be some hourly variation to cold supply (depending on plumbing layout eg underground and above ground supply pipes), but this is probably small. Monitoring in selected homes in capital cities would provide a point of comparison with the supply authority water temperature data, as well as indicate shorter term variations related to local conditions, which has some impact on overall energy consumption.

Hot water supply temperatures depend on both the water heater type and the settings. The storage temperature in electric off peak systems will decline during the day as hot water is drawn off and cold water is added to the tank. For gas and continuous electric storage systems, the tank thermostat should maintain consistent hot water outlet temperatures through the day and seasons. There may be exceptions where a household has an unusual pattern of hot water use with many frequent small draw-offs, which could lead to so called stacking in gas storage water heaters (accumulation of very hot water at the top of the tank). This is unlikely to be common during normal use.

Instantaneous gas hot water systems present a greater monitoring challenge because of the supply temperature of the hot water outlet. Units with electronic controls that preset at the point of use the fixed outlet temperature should be consistent through the year. Mechanical controls tend to provide a fixed temperature rise and this can vary with flow rate, so therefore the hot water outlet temperature can vary with cold water temperature and flow rate to some extent. This is complicated further by a user adjustable burner control (high/low) to adjust the burner rate for winter and summer operation. The most complicated is an electronic system with an external controller where the hot water delivery temperature can be independently selected by the user for each run. So in general terms, there is no option but to measure hot water conditions for these types.

The suggested strategy to determine supply temperatures and hot water energy delivery for all water heater types is to:

Continuously monitor cold water temperature at the water heater inlet; Continuously monitor hot water flow and the hot water temperature at the water heater outlet; To measure energy delivery it is necessary to use an integrating thermal energy meter that monitor water flow

rate and temperature rise and computes thermal energy delivery.

In addition, end use data would be improved substantially by undertaking continuous temperature monitoring at each shower. The preferred flow rates and showering temperatures can be determined at the beginning of the monitoring trial, so a flow meter on the shower is not necessary, and indeed this would be difficult to install in most cases. A temperature trace will give information about the timing and duration of showers in a non-intrusive way and the water flow meter on the water heat will enable hot water use to be allocated to the shower(s) unless there is another hot water outlet operating in parallel, which will be unusual.

3.8 Hot Water Energy Delivery The energy delivered in terms of hot water is a function of the volume of hot water delivered and the temperature rise from the cold water inlet to the hot water outlet of the water heater. To accurately determine delivered energy, all three parameters need to be estimated.

The most reliable way to measure hot water energy delivered is to use an integrating heat meter that looks at the temperature rise (from cold supply to hot delivery) and combine this with water flow to calculate total energy delivered. While heat meters provide the most accurate measure of energy, it is still very useful to have separate measures of hot and cold water temperatures and hot water volumes where possible.

Ideally some understanding of where hot water is being used will provide a better basis the overall household modelling hot water consumption, taking demographic factors into account. The majority of hot water is used in showers, but this will vary significantly across individual households. Determining the end use of hot water would require monitoring of hot water supply temperatures at a number of outlets around the home. Hot water usage at a particular point would appear as temperature spike in the supply pipe while water is used, and then it would gradually cool when water flow has stopped. This may be expensive for a large number of homes. It may be possible to track temperatures at three or four strategic hot water outlets. This temperature data has to be matched with hot water flow and temperature data metered at the water heater itself to be useful. Where clothes washers


and dishwashers are in a position to use hot water from the house supply (many have a cold-only connection, so they must heat their own water) their hot water use can be estimated from matching the time record of their electricity consumption (from an in line electricity meter) with the record of hot water drawoff from the water heater.

It is important to understand that average hot water consumption will vary substantially from house to house. On top of that, hot water consumption within each household is also likely to be highly variable from day to day. Hot water use is normally expected to be somewhat seasonal, although data from the REMP pilot homes did not exhibit much seasonal variation in the volume of hot water usage. So analysis techniques need to focus on methodologies on how to characterise this variability and where possible relate consumption back to the key demographic and other drivers.

Measurement of the hot water usage profiles needs to be the primary focus of any end use metering campaign. A good deal of engineering and modelling data exists that enables the input energy consumption of various water heater types to be estimated with good accuracy once a hot water delivery profile is known. Estimating the hot water consumption from water heater energy input data alone is usually impossible with any accuracy. Determining the field performance of water heaters during normal use (input energy and output energy) requires very extensive monitoring of numerous parameters (especially for types that interact with the environment, such as solar systems), so in many cases this is not practical.


There are several ways to collect data about household hot water use, water heater energy use and the factors influencing them. These include:

Surveys of physical characteristics of the water heater, the stock of hot water using appliances, household demographics and reported behaviour;

Monitoring the energy input into the water heaters (usually of limited value for more complex systems); Monitoring the time, volume and energy content of the hot water drawoff; Monitoring the use of hot water at key points (eg the shower, the clothes washer); Monitoring energy use only (this is relatively easy for controlled electricity tariffs, if all the energy through the

controlled tariff meter is used for water heating).

Generally, the approach that yields the most reliable data is a combination of survey and statistical techniques with actual monitoring of hot water use (plus water heater energy input where possible).

Using this approach, detailed metering of selected energy and hot water flows in a relatively small sample of households (of the order of 100 or so households) (which is the most expensive technical option) can be expanded to national estimates using larger scale surveys of households and census data.

This may need to be done in stages. Once the extent of variability in usage is established in smaller sample, it may be possible to estimate the sample sizes necessary to achieve given levels of confidence for the population as a whole (or at least key parts of it).

Without a detailed knowledge of the demographic and technical drivers of hot water consumption, it is not possible to correct for those demographic factors that may influence small end use metering samples when expanding these to estimate national hot water use. Nor will it be possible to accurately estimate future trends in hot water consumption.

A strategic approach to hot water consumption is required. It is recommended that three separate but related elements be undertaken in order to gather a more complete picture of hot water energy use. This will ensure the optimum use of limited resources. A notional indication of the scale of the task is provided at this stage. A more detailed analysis will provide a more accurate estimate of required sample sizes.

4.1 Element 1: High level survey (social and physical) combined with billing data (where available for separately metered systems)

A high level survey provides the most cost effective option to collect a range of demographic data together with ownership information (including brand and model of water heater) and billing data where this is available for separately metered appliances. The sample needs to be segmented in accordance with recognised demographic categories included in the Census. Aspects such as number and age of occupants, income details, housing details (size, type, rent/own), gas supply connected, urban/rural and selected appliance ownership data would need to be collected. In addition, billing records for electricity and gas would be collected (last two years of quarterly records collection through utilities is time consuming and slow)13.

It may be possible to use new innovative online techniques to collect much of the data. However, some segments (eg older, lower income) may still require face to face survey techniques. Some parameters like system details, solar configuration and solar orientation14 will usually require some site inspection by trained personnel in order to get accurate data.

13 Low energy water heaters (such as solar systems) may have low boost energy, which will be less apparent in utility bills. Dedicated off peak systems provide a direct measure of water heater input energy. 14 It may be possible to examine solar panel orientation from high resolution aerial photographs which are now readily available at no cost for many urban areas. See http://www.nearmap.com/help/map-features for an example.

4 Strategy for Quantifying Hot Water Energy


Nominally, a survey of several thousand households would be required to adequately cover all demographic categories and to allow an initial hot water end use model to be developed. Where quarterly gas billing data are available a conditional demand analysis (CDA) could provide good estimates of the share of gas use that goes to water heating, as distinct from space heating or cooking (if present). This does not yield any data on usage patterns or starts and only very coarse seasonal data (if any).

4.2 Element 2: Detailed hot water end use metering This is the most important element of an end use metering program. Hot water output would be measured by means of water flow meters integrated with hot and cold water temperature measurements or integrating heat meters. It would be advisable to include energy inputs as part of the data monitoring program for simple water heater types where possible. A sample of up to several hundred houses would need to be covered for an extended period in order to get sufficient data to develop a suitable demographic model of hot water use. However, the equipment requirements to collect this data are relatively modest when considered in isolation (a pulsing water meter, a data logger and two or three temperature sensors). As noted above, special techniques will be required to characterise the variability of hot water usage across different household types and from day to day within a household and to identify the key demographic drives for hot water use.

4.3 Element 3: Monitoring energy consumption of water heaters In this element, energy consumption of water heaters is directly metered. This should be done in conjunction with detailed hot water usage data (Element 2). The objective would be to quantify the overall performance of a range of water heater types in the field. A range of approaches will be required, depending on the water heater type:

Off peak electric storage systems daily energy consumption (where separately metered) (in reality it may be necessary to do this in real time at the switchboard);

Continuous electric storage systems real time energy consumption at the switchboard; All gas water heaters metering of gas consumption; Instantaneous gas water heaters with electric power real time electricity consumption at the appliance (this

will also provide data on the number of hot water events which is critical for this product, however monitoring period would need to be of the order of 2 minutes to identify duration of the hot water events);

Solar systems metering of boost input energy alone and hot water consumption will yield limited information for any type of solar boosted system. In addition ambient temperatures and solar radiation inputs need to be determined to enable more detailed system assessment through retrospective simulation;

Spot measurements of outlet temperatures for all storage systems.

Given that metering of gas consumption would require fitting of an in line gas meter, this could only be done in a limited number of sites. It would make sense to also fit temperature measurement devices and water flow devices to these same units (see element 3) as plumbers will have to be on site. Alternatively, it may be sufficient to meter total household gas consumption if other end uses can be disaggregated. The gas flow rate for each event together with a temperature trace on the water heater outlet could provide a means of identifying hot water events and allocating gas consumption to each of them.

In terms of monitoring data at the electrical switchboard, it would make sense to monitor other data such as whole house electricity as well as other end uses with a dedicated circuit (eg cookers, lighting, hot water) if a multi-channel recorder was to be used.

Accurately assessing all input energy into water heaters that use ambient inputs (solar and heat pump systems) is very difficult in the field and in most cases is not practical to any degree of accuracy. Monitoring hot water consumption for these units is a much higher priority

Significant expertise would need to be brought to bear on the data collected in Elements 1 to 3 to develop a detailed national hot water end use model. Different analysis will be required by different systems, especially storage versus instantaneous systems. It is likely that specific software will need to be developed to extract the most information out of monitored data.

Different methods of combining input energy, temperature and hot water flow energy could be trialled, to determine the most cost-effective means of collecting sufficient data for different water heater types.


4.4 Additional Macro Data The following data are necessary to model energy use and emissions, to explain where energy is used, and to support end-use policy appraisal and evaluation:

1. Stock attributes15 (eg capacity and efficiency) of water heaters by type by year by state and climate zone; 2. Sales and attributes of new water heater by type by year by state and climate zone; 3. Hot water consumption estimates (distribution) by time of year taking into account demographic and

technical drivers (and program impacts) as well as factors such as climate.

15 Typically stock attributes are determined from characteristics of new products flowing through a stock model.


Hot water is a significant end use in the home and is one which has been the focus of many energy policies over the past 20 years. The volume of hot water flow, the temperature of the cold water inlet and the hot water outlet can then be integrated to calculate the water heating energy delivered. The most robust approach is the use of a heat meter, which combines these elements. Metering the volume at the cold inlet is usually desirable for accuracy (accurate measurement for hot water is difficult, especially where temperatures vary a lot). Water heaters with falling water levels are rare but should be avoided as the inflow and outflow rates are not the same.

The other factor needed to calculate the energy efficiency of water heating is the input energy to the water heater. This is of great interest as it allows the energy output and the energy input of the water heater to be measured to give an assessment of overall in use energy efficiency. This is quite feasible for conventional fuel water heaters where the input energy can be readily monitored (eg gas or electric systems). This task becomes almost impossible for more complex systems with multiple energy inputs (eg solar thermal, solid fuel boosted systems) without very extensive instrumentation on the system and to measurement of ambient conditions16.

For hot water energy output (hot water flow), a plumber is usually required to fit a special flow meter on the hot water inlet (volume meter or heat meter). Temperature sensors can then be mounted on the inlet and outlet (ideally these should be in contact with the water).

For energy input, electric resistance systems will require metering at the switchboard (hard wired, high power). Heat pump systems can be metered with plug in data loggers. Gas systems require a gas meter to be fitted by a plumber. Experience with the REMP program has revealed that separate metering of each gas end use is really required to accurately assess energy inputs of each gas appliance.

If hot water output and input are both to be monitored, considerable equipment and expenditure are required.

Key considerations for hot water are:

Hot water volume is the most critical, along with inlet and outlet temperature (delivered energy); 1 minute data is really needed to see frequent small events that are very common (see next section Lessons

from the Pilot); Measurement of in service efficiency can be done approximately for conventionally fuelled products; Measurement of in service efficiency for solar products is extremely complex and expensive this requires a

large amount of monitoring equipment; Requires plumber to fit water meter and gas meter (where applicable); Day to day hot water use is highly variable.

16 From a policy perspective, what matters is the use of conventional fuels for boost energy. While measuring this does indicate the use of these fuels in real systems, it does not provide any understanding of why boost energy may be high or low for a particular house. So measuring the boost energy for solar systems really requires full system monitoring to be useful for field performance assessment.

5 Key Issues to Consider when Measuring Hot Water


Starting in February 2010, the REMP pilot project undertook detailed end use metering of five houses in Melbourne. This metering continued for over a year and included the installation of meters on each of the switchboard circuits, the 12 key (most used) lights, and 16 key appliances. Also installed were humidity and temperature sensors (both internal and external), in-line gas and water meters, occupancy sensors in major living areas and hot water temperature sensors in all there were around 60 individual channels (loggers) per house. The pilot project ultimately collected over 220 million datapoints, and provided both valuable insights into user behaviour and end use metering project challenges.

REMP monitoring has revealed that hot water usage patterns are extremely variable within a household and across households. The main drivers for this variation are not well understood. The key parameters for the 5 REMP homes are set out in Table 1

Table 1: Key Characteristics of Hot Water Consumption 5 REMP Homes

House Average litres hot water per day

Occupants Hot Water/ day/ Occupant L

Standard deviation of daily use L (CV)

1 144 4 36 74 (51%)

2 64 4 16 29 (45%)

3 107 4 27 62 (58%)

4 56 1 56 46 (82%)

5 68 2 34 30 (44%)

Average 88 3.8 23.1 N/A

Note: CV is the coefficient of variation = standard deviation over the mean. Hot water volumes are the measured volumes of hot water delivered by the water heater.

Hot water volume was recorded at 1 min intervals in the pilot homes. This revealed a large number of very small events in all homes. About half of all events are less than one litre and the drivers are not yet fully understood. This could be generated by tap use with so called flick mixers (their central position when off generates a mix of hot and cold water when lifted) but full investigations in the REMP houses are yet to be conducted. Four of the houses had 25 to 30 hot water events per day while the single person house had about 12 events per day. However, hot water consumption is fairly evenly distributed in event sizes up to 60 litres (for House 1 shown) as illustrated in Figure 3

6 Lessons from the Pilot


Figure 3: Distribution of Individual Hot Water Events House 1

In house 1, illustrated above, 46% of the hot water events were less than 1 litre in volume (this house uses an instantaneous gas water heater, so this is a critical point), and 75% of all events were less than 5 litres, which means that barely any hot water would be delivered for some of these events. These small events accounted for 15% of all hot water consumption in this house. Similar analysis of other REMP houses revealed similar data. The pilot has confirmed the importance of 1 minute hot water volume data in order to better understand hot water drivers17.

This is illustrated by the data on hot water event duration from House 2 below. In the REMP pilot homes more than half of all hot water events are 2 minutes or less in duration. Many of the events may be only 1 minute or shorter as all data was recorded at synchronised at 1 minute intervals rather than at the start or end of events.

17 If mixer taps turn out to be a key driver of small hot water events, it may be possible to characterise this aspect of hot water use by a survey where the users report the usual position and setting: this may be a clearer way to determine the prevalence of this practice is in the community.


Figure 4: Distribution of Hot Water Event Duration House 2 (6 months data)

The wide distribution of hot water loads suggests that traditional approaches for estimating hot water energy consumption during normal use may need to be reviewed. Simulation of the performance of the entire hot water system (including pipework losses) would be needed to determine the effect on energy use of high variability in events.

Further analysis may reveal whether there are any weather correlations with hot water use - this is critical for renewable energy systems (a larger sample would also be required to be reliable). Initial review of REMP pilot data revealed that there was no strong seasonal effect in hot water volumes. Seasonal usage of hot water is illustrated in


Figure 5. This shows that monthly usage in all homes is somewhat random in nature, but there is a pronounced dip in 4 of the 5 homes over summer (December to February). Review of the data suggests that this is due to absences from the house for holidays rather than a reduction in hot water use in summer. A more reliable way to characterise hot water use would be to estimate total energy consumption (hot water per occupied day) without absences and then correct (ex post) for an absences as they occur18. This would provide a more robust model for wider application. While it is true that the majority of absences due to holidays occur in the summer period, this is difficult to control with a relatively small end use sample, so data on absences should be obtained from larger scale surveys.

Daily hot water consumption in Appendix 3 gives a better impression of the day to day variability of hot water use.

18 Absences can be determined from hot water data and other parameters if measured (lighting is usually a good indicator, but also PIR sensors if used).


Figure 5: Relative Hot Water Usage by Month 5 REMP homes

A key area of research is also whether it is feasible to develop a demographic model of hot water consumption (and variability).

More hot water data from the REMP pilot homes is shown in Appendix 1


ABS4602 2005, Environmental Issues: People's Views And Practices, Australian Bureau of Statistics, December 2008. Available from www.abs.gov.au

AS/NZS 6400:2005, Water efficient productsRating and labelling

BIS 2008, The Household Appliances Market in Australia 2008, VOL 4: HOT WATER SYSTEMS, BIS Shrapnel, Sydney. Available by subscription.

BRANZ 2007, Energy Use in NZ Households: Report on the 10 Year Analysis for the Household Energy End-use Project (HEEP), Building Research Establishment of NZ, available from www.branz.co.nz

DSE 2008, H2OME: A guide to permanent water savings in your home, Department of Sustainability and Environment, Victoria, January 2008.

EES 2004, Hot Water Time of Use Data, prepared by Energy Efficient Strategies for EL20, March 2004.

EES 2008, Energy Use in the Australian Residential Sector 1986 2020, prepared by Energy Efficient Strategies for the Department of the Environment, Water, Heritage and the Arts, June 2008. Available from www.energyrating.gov.au in the electronic library.

EES 2009, Hardware for End-Use Measurement: assessment of potential technology, prepared by EES, Robert Simpson and Kevin Lane for DEWHA, July 2009 (working draft).

Greenworld 2007, A Pilot Study of the Impact of 3-star Showerheads on Household

Water Consumption, Greenworld Energy for Yarra Valley Water, November 2007.

Guthrie and Kimpton, Pilot Study to Define the Patterns and Quantities of Domestic Hot Water Consumption in Victoria, by Ken Guthrie and N.C. Kimpton, Victorian Solar Energy Council, January 1987, part of NERDDC project 817.

GWA 1993, Benefits and Costs of Implementing Minimum Energy Performance Standards for Household Electrical Appliances in Australia, by George Wilkenfeld & Associates (with Lawrence Berkeley Laboratory), for State Electricity Commission of Victoria, July 1993. Chapter 7 electric water heaters. See http://www.energyrating.gov.au/library/detailsgwa-meps1993.html

GWA 2004, Regulation Impact Statement: Proposed National System of Mandatory Water Efficiency Labelling for Selected Products, George Wilkenfeld and Associates for the Department of the Environment and Heritage, Australia, May 2004.

GWA 2005, Expanding the Australian Water Efficiency Labelling and Standards (WELS) Scheme: Final Report, George Wilkenfeld and Associates for the Department of the Environment and Heritage, Canberra.

GWA 2006, Water Saving Requirements for New Residential Buildings in Victoria:

Options for flexible compliance, George Wilkenfeld and Associates for the Department of Sustainability and Environment, May 2006.

GWA 2007, Specifying the Performance of Water Heaters for New Houses in the Building Code of Australia, by George Wilkenfeld & Associates (et al) for the Australian Building Codes Board, December 2007.

GWA 2008, For Consultation: Regulation Impact Statement: Minimum water efficiency standards for clothes washers and dishwashers and water efficiency labelling of combined washer/dryers, George Wilkenfeld and Associates for the Department of the Environment, Water Heritage and the Arts, September 2008.

GWA 2010, Decision Regulatory Impact Statement Phasing Out Greenhouse Intensive Water Heaters in Australian Homes, George Wilkenfeld and Associates with National Institute of Economic and Industry Research, for the National Framework for Energy Efficiency, November 2010.

7 References


ISF 2008, Analysis of Australian Opportunities for More Water-Efficient Toilets, Institute for Sustainable Futures. for the Department of the Environment, Water, Heritage and the Arts, 2008.

Marsden Jacob 2006, Securing Australias Urban Water Supplies: Opportunities and impediments. A discussion paper prepared for the Department of the Prime Minister and Cabinet, November 2006.

Pacific Power 1995, The Residential End-Use Study, see http://www.energyrating.gov.au/library/detailsresidential-execsumm.html for executive summary.

SECV 1970, Williamstown Hot Water Study, prepared by Jim Lacey from the STATE Electricity Commission of Victoria and the study was undertaken jointly with the City of Williamstown (electricity supply) and the Housing Commission. (summary included in EES 2004).

SEW 2008, Household Waterwise Makeover Program 2007-08, South East Water, August 2008.

WSAA 2008, National Performance Report 2006-07: Urban water utilities. Water Services Association of Australia (WSAA) and National Water Commission.

YVW 2005, Yarra Valley Water 2004 Residential End Use Measurement Study, Yarra Valley Water, June 2005.

YVW 2008, 2007 Appliance Stock and Usage Patterns Survey Asoka Athuraliya, Kein Gan and Peter Roberts, Yarra Valley Water, May 2008.

.


Total energy consumption of metered gas and electricity of the 5 homes over a year is illustrated in

Figure 6 this is useful as it gives a total overall comparative snapshot of the metered energy sources. House 3 had a highest gas and electricity consumption and is well above the state average (it is the largest physical house). Houses 1 and 2 had more typical gas consumption (closer to the Victorian average). Houses 4 and 5 had quite low gas consumption (on further analysis, this was for good reasons). The data presented needs to be put in the context of typical energy consumption of gas in Victoria values of 60GJ a year are a typical value for residential, so the data needs to be considered in this context (heating loads in Victoria are considerably higher than all other mainland states for a range of reasons). Also the Victorian summer of 2010/2011 was very mild with few hot days, so air conditioner use and peak loads were considerably lower than normal. All monthly data is for the year May 2010 to April 2011.

Figure 6: Total Energy Consumption 5 REMP homes

The monthly distribution for each of the 5 homes is illustrated in the following figures. Houses 1 to 3 showed very strong seasonal gas consumption. House 4 had low gas use as there is a single occupant who keeps unusual hours. House 5 had no gas space heating, so gas is only used for hot water and cooking. Houses 2 to 5 had gas storage hot water, House 1 had an instantaneous gas hot water system.

Appendix 1 Further Pilot Study Data


Figure 7: Monthly Electricity and Gas REMP House 1



Daily Hot Water Consumption

The next series of figures illustrates the daily hot water consumption of the REMP pilot homes. This shows high variability from day to day and in most cases no strong seasonal pattern in terms of hot water volume (there will be some seasonal effects on energy due to changes in cold water temperatures and increased heat losses for tank systems in winter). REMP pilot house 3 is not shown as there is too much missing data.

House 1 were away for some of October and January.

Figure 12: Daily Hot Water Consumption REMP House 1


House 2 were away for some of January as well.



Figure 15: Time of Day Gas Consumption for REMP House 4


Time of Day Hot Water Use

The following figures show hot water use by season by time of day.

Figure 16: Hot Water Use by Time of Day REMP House 1


House 2 has very young children.



The interesting finding is that time of day usage is not obviously seasonal. All houses exhibit strong morning peaks in hot water use and most also show strong evening peaks, although these are more variable in their timing and size. The houses vary from being slightly morning dominant to slightly evening dominant, but in practical terms there is quite a lot of hot water use throughout the day in the REMP pilot homes. Note that the vertical scales vary on these figures.

The following figures provide more detail on REMP House 1 (instantaneous gas water heater) in terms of event sizes, starts and litres per day.


Figure 21: Hot Water Event Volume Distribution REMP House 1

Figure 22: Hot Water Litres Per Day Distribution REMP House 1


Figure 23: Hot Water Starts Per Day Distribution REMP House 1

The above distribution is a count of individual hot water events in each day of operation. For analysis purposes, events that were less than 0.2 litres were ignored.

REMP Water Heating Data Collection and Analysis

www.energyrating.gov.au

A joint initiative of Australian, State and Territory and New Zealand Governments

Date post:	05-Sep-2015
Category:	Documents
Upload:	dgg
View:	217 times
Download:	0 times

Water Heating and Data Collection

Documents