A New Study of Hot-water Use in Canada.


In Canada, approximately 347 PJ (3.3 X .sup. Btu) of energy,

or 9.5 billion [m.sup. (335 billion [ft.sup.) of natural gas

equivalent, are used to heat water for residential and commercial use on

an annual basis, and this leads to approximately 18 megatons (18

megatons) of [CO.sub. equivalent GHG emissions. Given the relative

difference in population size, the emissions from the U.S. will be in

the order of ten times that of Canada.

The basis for the current water-heating appliance performance

standards in North America was established and came into effect about 17

years ago, during which time testing and monitoring equipment has

improved, water-heating technologies have improved, and people's

habits have changed. This has led us (Natural Resources Canada) and

others in North America to ask the question, "Are these performance

standards still appropriate, and what changes could be made, if

necessary, to make them more appropriate?" Given that modern test

equipment is capable of logging and controlling a test to within a

second, we could, if it seems appropriate, change the draw schedule to a

more realistic use pattern. In any modified performance rating, we could

also consider how the efficiency of a water heater may vary with how

much hot water is used on a daily basis. Prior to the initiation of this

study, it was thought that hot-water use may have decreased due to the

introduction of water metering, the widespread use of low-flow shower

heads, the practice of cold-water clothes washing, and the common use of

aerators on hot-water taps.

One step in answering the above question was to compare the

real-life water-use patterns from a new field study to that of the

water-draw patterns used in the current water heater performance

standards, i.e., typically 6 draws of 40.6 L (10.7 gal) at a rate of

10.4 Lpm (3.0 gpm), each an hour apart and then followed by 18 hours of

standby. To that end, in 2007/2008, the Renewables and Integrated Energy

Systems Group at Natural Resources Canada (NRCan), a department of the

Canadian Federal Government, initiated a new study of residential

hot-water use with the aim of determining whether there had been any

significant change in hot-water use since the last study was conducted.

The NRCan study utilized low-cost data loggers together with accurate

flowmeters to monitor the volume of hot water drawn every two to four

seconds, for a period of approximately two to three weeks, in each home.

This first stage of the study monitored 38 households in the greater

Ottawa area. NRCan has now extended the hot-water use monitoring to

include 36 households in Hamilton, London, and Sudbury, in the province

of Ontario. This second stage of the study was conducted in

collaboration with Union Gas, Ltd., and with the assistance of Caneta

Research, Inc., adding another 37 households to the study. With a total

of 74 test sites monitored, our monitoring is believed to be the largest

such study of its kind conducted since the earlier work completed by

Perlman and Mills (1985), and by work conducted by L.G. Spielvogel.

In Canada, the performance test standard for residential gas-fired

storage water heaters is the CSA P.3 (CSA 2004a), for residential

instantaneous water heaters it's the CSA P.7 (CSA 1998), and for

residential electric storage water heaters it's the CSA C191 (CSA

2004b). In the US, the performance tests for the above three water

heater types is specified in the DOE Code of Federal Regulations, Title

10, Part 430, Appendix E to Sub-Part B. The DOE test is also reflected

by ANSI/ASHRAE Standard 118.2-2006, Method of Testing for Rating

Residential Water Heaters. The ASHRAE standard is generalized and has

the specific test parameters required by the DOE listed in an appendix

to that document (Annex A). In Canada, the performance test for electric

storage water heaters, the CSA C191, is significantly different to that

used in the U.S. because it is a standby energy loss only test.

Excepting the CSA C191 test, each of the other performance tests uses a

parameter called the energy factor (EF) as a measure of efficiency. The

EF is calculated as the ratio of the energy delivered to the end user as

hot water, divided by the total energy consumed by the water heater over

a 24-hour period in a simulated use test.

Because of the different operating characteristics of storage and

instantaneous water heaters, changes to the total volume of hot water

drawn per day and the draw schedule employed in the performance test

standards will have different effects on the energy factor derived for

each of these product types. For example, The Davis Energy Group has

found that the real-use efficiency of instantaneous water heaters can be

reduced by 8.8% when regular infrequent short draws of hot water are

made. NRCan has conducted its own study, which has confirmed the Davis

Energy Group's noted drop in efficiency due to cyclic operation for

tankless water heaters, as shown in Table 1.

It is also known that the real-use efficiency of storage water

heaters is greatly affected by the length of time they spend on standby

in comparison to the time spent in operation. The efficiency of a

storage water heater could easily be reduced by 10 percentage points

if the daily use of hot water is reduced by about 22 gal. Using the

current test standards, the efficiency (EF) of installed gas-fired

storage water heaters in North America ranges from about 50% to 64% (up

to 86% if condensing) and, in comparison, the efficiency of gas-fired

instantaneous water heaters ranges from 80% to 85% (up to 98% if

condensing). As discussed above, however, in the real world these

efficiencies may be significantly different depending on how the water

heater is used in practice.

It can be seen that in any potential redesigning of the water

heater performance test standards it will be necessary to take into

account the parameters that can affect the operating characteristics of

the different water heater types and also to have an accurate

understanding of the general population's daily hot-water use and

usage habits. The results of this study, presented here, aims to help

provide current information with regards to residential hot-water usage



Equipment Utilized

The equipment employed in the hot-water use study can be found in

Appendix A.

General Methodology

The following general methodology was used. Further detail can be

found in Appendix A.

1. Assemble equipment required (test to ensure functionality).

2. Recruit volunteers.

3. Group volunteers by geographic location.

4. Install monitoring equipment and monitor for a minimum of two


5. Provide each homeowner with a questionnaire.

6. Remove equipment and restore to original condition.

7. Process data and analyze results.

Information is presented relating to the key parameters, used in

the CSA P.3, CSA P.7, the DOE, and ANSI/ASHRAE Standard 118.2

performance test standards (CSA 2004a; CSA 1998; DOE 2004; ASHRAE 2006),

i.e., average daily hot-water use, the average number of hot-water draws

per day, the average volume of hot water used per draw, and the average

draw volume flow rate.


During the first stage of the study we set the data logger to

record hot-water use every two seconds in order to define with some

accuracy when different water draws were taking place; however, we found

that there were many single pulse events throughout the day, at all of

the test sites monitored, with the total number of draws exceeding 200

in most cases. In discussing our preliminary results with other experts

in the field, we decided to eliminate all of these single pulse events

from our data (this had a significant effect on the number of draws per

day but only changed the average volume of hot water used per day by

less than 1% at each test site). It was thought that these single pulse

occurrences were probably due to water pressure changes and/or

convection currents in the water pipes, triggering a pulse at the

flowmeter. Anything more than a single pulse by itself was considered to

be a genuine hot-water draw.

Daily Hot-Water Use

One key result from the study indicated that hot-water use appeared

to have reduced over the last 17 years (as shown in Figures 1 and 2),

with 83% of the monitored test sites using less than 243.4 L/day (64.3

gal/day) at an average value of 185.6 L (49 gal) per day. This is

approximately 60 L (or 16 gal) per day less than the current performance

test standards assume. This change in total daily volume of hot water

used is unlikely to have any impact on a gas-fired tankless water

heater, but because of the longer duration on standby, a gas-fired

storage water heater may see a reduction in EF on the order of 0.10,

i.e., a 10 percentage point reduction in its efficiency, as discussed in

the introduction.



The study median (Figure 2) was found to be very similar to the

study average value (Figure 1) for the daily volume of hot water used

per household, indicating a possible normal distribution; however,

normality will need to be definitively verified through lengthier

analysis, at a later date. Note that the data collected from test site

30 in the second stage of this study were corrupted and could not be

used in our analysis. All other sites had usable data. Test Site 12 data

were examined because of its high hot-water use, but only one unrelated

error was found in the data, which did not account for the high use, and

several distinct large-volume water draws were identified manually.

Family Size and Hot-Water Use

Statistics Canada Data indicates that the average family size has

decreased from 3.7 down to 3.0 over the last 35 years or so. From our

study, family size did not seem to be a significant indicator of daily

hot-water use. For comparison to other populations, the family

configuration of the study participants is shown in Figure 3. In this

graph, the key indicates the number of adults and children per

household. It should be noted that some participants did not provide

this information to us and thus could not be included in the chart. The

only apparent conclusion to be made from this information was that you

could not assume that smaller families use less hot water and that

larger families use more hot water.


Water Heater Type and Hot-Water Use

It has been speculated that end users with tankless water heaters

use more hot water than those with storage water heaters. This thought

arises from the fact that a tankless water heater has an endless supply

of hot water, whereas the supply of hot water in a storage water heater

is effectively limited by the tank capacity. Another contributing factor

could also be the nature of the operation of a tankless water heater;

i.e., the water flow rate must reach a pre-set minimum level before the

burner fires to start heating the water; subsequently, there is also a

short delay (

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