Summary of Canadian Domestic Water Heating Research (Using kWh)

Based on the 2005 CBEEDAC report “Domestic Water Heating and Water Heater Energy Consumption in Canada” (Aguilar et al., 2005), alongside recent findings from Abdeen et al. (2020, 2021), we have reviewed our OBJECTIVE framework’s domestic hot water (DHW) energy consumption model (values expressed in litres and kWh, where lpppd = Litres per Person per Day).

Key Findings

Total Water Use/Person (Litres)	DHW Use/Person (Litres) typ 40% of Total Water	DHW Use/Household (Litres)	Avg. Household (persons – Census)	kWh/Household	Source
343	137.2	349.86	2.55	6,691.42	Environment Canada
275	110	280.5	2.55	5,364.84	OBC 8.2.1.3.A
262	104.8	267.24	2.55	5,111.23	USA, Mayer et al.
236.6	94.64	241.33	2.55	4,615.68	Ecotope, Seattle (MURB>20 Units)**
220.56	88.23	225	2.55	4,303.35	NBC 9.36
151.07	60.43	154.09	2.55	2,947.08	Abdeen et al.
123.13	49.25	125.6	2.55	2,402.23	Hot2000 (NRCan)
62.5	25	63.75	2.55	1,219.28	PHPP/PHI
220	88	224.4	2.55	4,291.87	OBJECTIVE

Total Water Patterns (Hot + Cold)

• NBC 9.36 cites a DHW usage of 225 litres DHW use per SFR Household, which varies from 2.55 persons/household per Canadian Census data, to 2.9 persons based on the Ontario Energy Board’s Technical Resource Manual (OEB TRM), and 1.9 persons/household in MURBs.
• OBC 8.2.1.3.A provides a table of total water use (Hot & Cold) and for Residential uses assumes 275 litres total water use per person/day.
• Canadian daily residential per capita total water use was estimated at 343 litres/day in 1999, up from 327 litres/day in 1996, similar to levels in 1989 (347 litres/day) (Environment Canada, 2004)
• This is significantly higher than U.S. estimates, which reported average per capita indoor water use of 262 litres/day (Mayer et al., 1999)
• Canada has among the highest per-capita water consumption rates worldwide (Environment Canada, 2004)
• Recent comparative review by Abdeen et al. (2020, 2021) indicates the current National Building Code (NBC) of Canada assumption of 225 L/day DHW use may not reflect typical current use patterns[1]

DHW Patterns

• From above, NBC thus assumes ~88.23 lpppd DHW use (household by census average)
• Ecotope of Seattle arrives at a 25gpdpp (PEAK)** figure from MURBs, or 94.64 lpppd of DHW.
• The Abdeen et al. (2021) study found a clear linear correlation between daily Canadian DHW consumption and occupancy, proposing the formula: QDHW = 50.25 × Nocc + 13.2 L/day[1] which equates to 63.45 lpdpp for 1 person, 113.7 for 2, 163.95 for 3 and 214.12 for 4.
• Hot2000 (the software used for residential EnerGuide, EnergyStar and R2000 programs in Canada) assumes QDHW = 26.94 × No.Bedrooms + 56.9 L/day, which for a 2BR home would be 110.78 litres DHW and 137.72 litres DHW for a 3BR home.
• PHPP and Passive House assumes a much lower value, possibly reflecting EU-experience, of 25 lpppd DHW use, so with a household of 3, this would be only 75 litres DHW, which is 46-54% lower than the typical Canadian averages ~ (if your PHI project fails to show utility results like your PHPP model, this may be why…)

Hot Water as Percentage of Total Water

• Per NBC and Census data, 88 DHW/220 TOTAL = 40% of Total Water as DHW
• And 39.6% of total residential water use is hot water per (DeOreo and Mayer, 2000)
• This translates to about 138.6 lpppd of hot water (range: 106.5-181 liters/person/day)
• Personal use (showers, baths, faucets) accounts for 43-53% of total hot water consumption (Henze et al., 2002; DeOreo and Mayer, 2000)

Energy Requirements

• Domestic water heating accounts for approximately 22% of total household energy consumption in Canada, making it the second-largest energy end-use after space heating (NRCan, 2004a)
• In the Canadian residential sector, DHW demands account for 18% of all energy end-use and 3% of the total secondary energy consumption, approximately 80,222 MWh (288.8 PJ) annually[1]
• DHW-related Energy consumption varies significantly by fuel type (US DOE, 2000a):
  • Electric: 3,460 kWh/year per household
  • Natural gas: 6,856 kWh equivalent/year per household
  • Oil: 7,517 kWh equivalent/year per household
  • LPG: 6,680 kWh equivalent/year per household
• OBJECTIVE formerly budgeted 986.06kWh/pp/yr for DHW use. At ~2.55persons/household, would have us on the low end of the threshold at 2,514 kWh/household/yr.
• Australia uses ~2,190kWh/yr/household as an average value

Hot Water Equipment Efficiency

• Energy Factor (EF) values used in Canadian models (Aguilar et al., 2005):
  • Electric: 0.84864
  • Natural gas: 0.52985
  • Oil: 0.52369
  • Propane: 0.50
• Heat pumps, such as indoor 110VAC or outdoor systems tied to ASHP systems can exceed 300% of have an EF of 3.0 (Same as COP).

Household Factors

• Household size significantly impacts water consumption (Mayer and DeOreo, 1999)
• Per-capita consumption decreases as household size increases (household efficiencies)
• Average Canadian household size was 2.55 persons (Statistics Canada, 2001)
• The OEB TRM uses 2.9 occupants/household for SFRs and 1.9 occupants per household for MURBs
• The CBC study by Abdeen et al. (2021) found a clear linear correlation between daily DHW consumption and occupancy, proposing the formula: QDHW = 50.25 × Nocc + 13.2 L/day[1]
• Hot water use increases with income – approximately 11.6 kWh/year (0.0418 GJ/year) for every $1,000 increase in yearly income (Aydinalp et al., 2004)

Regional Variations

• Natural gas is the primary hot water fuel from Ontario westward (Statistics Canada, 2002)
• Electricity dominates in Quebec and the Maritimes (except PEI)
• British Columbia and Manitoba show more balanced use of electricity and natural gas
• Very few retrofits involve changing the fuel type for domestic water heating, but note the date of the study (Aguilar et al., 2005)

Temporal Patterns and Seasonality

• The NBC’s hourly schedule for DHW use is significantly different from measured data sources, particularly in timing and magnitude of morning and evening usage peaks[1]
• Morning peak consumption typically occurs between 6-7 a.m. in observed data versus 9-10 a.m. in NBC assumptions[1]
• Evening peak consumption occurs between 6-7 p.m. in observed data versus 4-5 p.m. in NBC assumptions[1]
• Winter DHW consumption is approximately 24.1% higher than Summer consumption, with winter usage 16.7% above the annual average and summer usage 11.4% below average[1]

Conclusions for OBJECTIVE

1. Adjust Water Consumption Estimates

Our assumption of 225-275 lpppd Total Water Use, while it may be on the lower end of actual Canadian usage is nevertheless derived from required values in the NBC and OBC variously from 225 to 275 lpppd, and so we will retain this as a baseline default – and we recommend this baseline for new construction, with better practices, heat traps, good tank and pipe insulation, no leaks, and good equipment efficiency. Some of the research showed higher losses due to convective looping, recirculation loops (ie. for large buildings like hotels to maintain faster delivery of hot water) and leaks (anecdotal from sources). None of this research included projects with DWHR systems (Drain Water Heat Recovery systems) which can significantly reduce demand in a range of 40-70%, especially in larger buildings with many occupants (constant DW flow). We will add a note to the user that 343 lpppd will approximate a more realistic baseline for conventional SFR projects (Environment Canada, 2004), with adjustments for:

• Regional Total Water differences (metered: 269 L/day vs. unmetered: 457 L/day) (Environment Canada, 2004)
• Urban vs. rural settings
• Household size efficiencies
• Influence of Income of Totals (11.6 kWh/$1k income over baseline)
• Incorporate the formula from recent findings: QDHW = 50.25 × Nocc + 13.2 L/day[1]
• Noting that ~40% of total Water use is DHW

2. Hot Water Percentage

Using 39.6% as the baseline percentage of total water that is heated (DeOreo and Mayer, 2000), which on the lower default would give approximately 89-110 lpppd DHW and 135-140 lpppd of DHW as a more ‘realistic’ estimate.

3. Energy Factor Refinements

The efficiency values in our model should vary by fuel type (Aguilar et al., 2005):

• Electric: 0.85-0.95 (newer models)
• Natural gas: 0.53-0.67 (higher for commercial condensing models, tbc by engineering)
• Oil: 0.52-0.59
• Propane: 0.52-0.63
• Heat Pump >2.5

4. Modeling Improvements

• Incorporate standby losses that vary by fuel type (US DOE, 2000a) – noting that standby losses become internal equipment gains, slightly reducing thermal energy demand (TED), but has the effect of increasing DHW demand beyond what the equipment rating itself provides:
  • Electric: ~825 kWh/year (2.97 GJ/year)
  • Natural gas: ~3,170 kWh/year (11.4 GJ/year)
  • Oil: ~3,280 kWh/year (11.8 GJ/year)
• Account for distribution system losses (5-10% of total hot water energy) (Wiehagen and Sikora, 2002b)
• Consider household size and income as multiplier factors
• Update DHW usage schedules to reflect actual consumption patterns, with morning peak between 6-7 a.m. and evening peak between 6-7 p.m.[1]
• Note that incoming water supply temperature is ~10ºC (PHPP assumes 7ºC), and is raised to ~55ºC by SHW equipment, the kWh (assume 100% efficiency) to raise water over this gradient would be 0.0523 kWh/litre (this tends to over-estimate required DHW energy 2x that of our legacy method in OBJECTIVE 3.032 and earlier versions).

5. Additional Variables to Consider

• Seasonal variations (10-13% increase from Summer to Winter) (Goldner, 1994)
• Winter consumption 24.1% higher than Summer, 16.7% above average[1]
• Weekend vs. weekday usage patterns (~7.5% higher on weekends) (Goldner, 1994)
• Inlet water temperature variations by region (Abrams and Shedd, 1996) (we assume 10ºC)
• Household demographic factors (age of occupants) (Lutz et al., 1996)
• Presence and efficiency of hot water-using appliances (Wenzel et al., 1997)
• Baseload energy requirements (standby losses) (Pratt et al., 1993)
• Rural Systems may use heat tracing, which could be considered either a site load or as part of the water system loads
• When buildings are electrified, yet SHW or DHW remains gas-fired, it can be easier to correlate actual use patterns from gas use, water use, and nameplate equipment efficiencies (we are reviewing this on several MURBs presently).

Validation of OBJECTIVE’s Current Estimate

Our current estimate of 986.06 kWh/person/year for DHW energy appears to be on the lower end when compared to the research findings, especially if applied universally across fuel types. For a typical Canadian household of 2.55 persons:

• Electric: ~1,360 kWh/person/year
• Natural gas: ~2,690 ekWh/person/year
• Oil: ~2,950 ekWh/person/year

A more accurate approach would be to develop water consumption models by occupancy, household size, and region, divide out a percentage of this (~40%) as DHW, and apply a physics-based calculation method that correlates to the observed energy intensity of DHW totals from Canadian sources, adjusted by fuel-type and equipment efficiency as these factors all significantly impact hot water energy use patterns (Aguilar et al., 2005; Abdeen et al., 2021).

We are now considering an adjustment to our default residential DHW use profiles, where we will assume 220 lpppd total water, 88 lpppd of which is DHW (~40%), which on a ‘census average’ household of 2.55 persons gives 224.4 litres/day of household DHW use, which when multiplied by 0.0524kWh*365 days = 4,291.87 kWh/yr for DHW use, placing us in the mean of the methods defined in the table above, respecting NBC 9.36 defaults, but arriving at a value closer to actual use from the literature review. We will review our existing case study buildings for accuracy of ‘fit’ to our current data. As a single yet significant building-related load, this can present a hidden or otherwise under-explained aspect of buildings far exceeding modelled performance values when validated against utility bills.

References

1. Abdeen, A., O’Brien, W., Gunay, B., Newsham, G., & Knudsen, H. (2021). Investigation of occupant-related energy aspects of the National Building Code of Canada: Energy use impact and potential least-cost code-compliant upgrades. Science and Technology for the Built Environment, 27(10), 1393-1424.
2. Abrams, D.W. and A.C. Shedd (1996), “Effect of Seasonal Changes in Use Patterns and Cold Inlet Water Temperature on Water-Heating Loads”, ASHRAE Transactions: Symposia, AT-96-18-3, 1038-1053.
3. Aguilar, C., D.J. White, and D.L. Ryan (2005), “Domestic Water Heating and Water Heater Energy Consumption in Canada”, CBEEDAC 2005-RP-02.
4. Aydinalp, M., V.I. Ugursal, and A.S. Fung (2004), “Modeling of the Space and Domestic Hot-Water Heating Energy-Consumption in the Residential Sector Using Neural Networks”, Applied Energy, 79, 159-178.
5. DeOreo, W.B., and P.W. Mayer (2000), “The End Uses of Hot Water in Single Family Homes from Flow Trace Analysis”, Aquacraft Inc. Report.
6. Environment Canada (2004), “Urban Water: Municipal Water Use and Wastewater Treatment”, National Environmental Indicator Series Archives, SOE Bulletin No. 2001-1.
7. Goldner, F.S. (1994), “Energy Use and Domestic Hot Water Consumption”, New York State Energy Research and Development Authority, Report 94-19.
8. Henze, G.P, D.K. Tiller, M. Fischer, and M. Rieger (2002), “Comparison of Event Inference and Flow Trace Signature Methods for Hot Water End Use Analysis”, ASHRAE Transactions, 108, Part 2, 467-479.
9. Lutz, J.D., X. Liu, J.E. McMahon, C. Dunham, L.J. Shown, and Q.T. McGrue (1996), “Modeling Patterns of Hot Water Use in Households”, Ernest Orlando Lawrence Berkeley National Laboratory Report LBL-37805 Rev.
10. Mayer, P.W., W.B. DeOreo et al. (1999), Residential End Uses of Water, AWWA Research Foundation and American Water Works Association.
11. Natural Resources Canada (2004a), “Energy Efficiency Trends in Canada, 1990 to 2002”, Office of Energy Efficiency, June.
12. Natural Resources Canada (2004b), Energy Use Data Handbook, 1990 and 1996 to 2002, Office of Energy Efficiency, June.
13. Pratt, R.G., B.A. Ross and W.F. Sandusky (1993), “Analysis of Water Heater Standby Energy Consumption from ELCAP Homes”, Energy and Buildings, 19(3), 221-234.
14. Statistics Canada (2001), 2001 Census.
15. Statistics Canada (2002), Survey of Household Spending User Guide Public Use Microdata File.
16. U.S. Department of Energy (2000a), “Technical Support Document: Energy Efficiency Standards for Consumer Products: Residential Water Heaters, Including: Regulatory Impact Analysis”.
17. Wenzel, T.P., J.G. Koomey, G.J. Rosenquist, M. Sanchez, and J.W. Hanford (1997), “Energy Data Sourcebook for the U.S. Residential Sector”, Ernest Orlando Lawrence Berkeley National Laboratory Report LBNL-40297.
18. Wiehagen, J. and J.L Sikora (2002b), “Performance Comparison of Residential Hot Water Systems”, National Renewable Energy Laboratory Report NREL/SR-550-32922.
19. OEB Technical Resource Manual, 2021
20. 2020 NBC & OBC & NECB Building Codes
21. OpenBuilding OBJECTIVE TEUI3 versions 3.030 through 3.033

**One must be careful that you are distinguishing between use estimates used for SIZING EQUIPMENT vs. use estimates used for ESTIMATING ENERGY USE. The 25Gal PPPD number referenced for Ecotope is a peak value used for sizing DHW systems for multifamily buildings. If you size your water heating system for 25Gal PPPD you will have enough hot water for almost any condition to be expected in a building with more than about 20 units ~ Ecotope