Household Energy End-Use Project - Hot water

The BRANZ HEEP project final report contains a large amount of research, data and analysis on NZ's domestic hot water systems and energy use.

The full report (366 pages) is available for download and viewing online here.

Selected table of contents items relating to hot water systems and energy use:

15.1 Hot water heating – the shift to gas
15.2 House size, energy use and sustainability

16.1 Introduction
16.2 Method
16.3 Comparison with Modera’s Equation
16.4 Results
16.5 Conclusions

24.1 Introduction
24.2 Hot water today
24.3 Providing domestic hot water
24.4 International comparisons
24.5 Hot water Energy Use
24.6 DHW energy use distribution
24.7 System types
24.8 Estimates of wet-back energy heat inputs
24.9 Storage cylinders
24.10 Baths and showers
24.11 Shower water flow
24.12 Water temperatures
24.13 Improving cylinder thermal performance
24.14 Costs
24.15 Improving cylinder electricity efficiency
24.16 Cylinder wraps in reality
24.17 Reducing hot water energy use
24.18 Conclusions

Until piped water
Beginnings of piped hot water
History of electric hot water
History of gas hot water
Figure 123: Examples of hot water cylinders
Figure 124: Residential use of storage electric hot water systems
Figure 125: Selected nations - electric hot water cylinders by capacity
Figure 126: DHW Fuels
Figure 127: Variation in proportions of energy end-uses
Figure 128: Variation in energy end-uses
Figure 129: DHW Energy use distribution – all fuels
Figure 130: DHW electricity distribution
Figure 131: DHW gas distribution
Figure 132: DHW Wetback distribution
Figure 133: Average DHW energy profiles
Figure 134: Monthly hot water energy profiles
Figure 135: National Hot Water Energy Use by Month
Figure 136: DHW Energy use by month
Figure 137: DHW Energy Use by Month for Houses with that fuel
Figure 138: Changing estimates of NZ residential energy end-uses
Figure 139: Energy consumption and standing losses by system type
Figure 140: Hot water systems – by type and houses
Figure 141: Cylinder volumes
Figure 142: Cylinder size by region
Figure 143: Cylinder size by age
Figure 144: NZ Sales by capacity of electric DHW cylinders 2004/5
Figure 145: System pressure by region
Figure 146: Pressure by house decades
Figure 147: Pressure by cylinder decades
Figure 148: System age by location
Figure 149: 135 and 180 litre cylinders by decade of manufacture
Figure 150: Cylinder manufacture compared to house construction decade
Figure 151:Total hot water volume vs floor area
Figure 152: Total hot water volume vs number of occupants
Figure 153: Single electric DHW systems – litres per person
Figure 154: Use of baths and showers 1971/72
Figure 155: Use of baths and showers HEEP
Figure 156: Household DHW volume 1971/72
Figure 157: Household DHW volume HEEP
Figure 158: Self-reported shower duration – histogram
Figure 159: Tap temperature by system type
Figure 160: Distribution of hot water tap temperature by electric cylinder volume
Figure 161: Variation between thermostat setting & delivered water temperature
Figure 162: Adult skin (full thickness) epidermal burn time
Figure 163: Hot water temperature vs occupant average age
Figure 164: Thermostat setting distribution
Figure 165: Tap temperature distribution
Figure 166: Thermostat setting vs tap hot water temperature
Figure 167: Negawatt cylinder wrap
Figure 168: Examples of electric hot water cylinder wraps

Figure 184: NZ Census 1945-1996 Domestic Hot Water by fuel type
Figure 185: NZ Census 1945-1996 % Dwellings with no DHW
Figure 186: NZ Census 1976-1996 Dwellings with only one DHW fuel
Figure 187: 1981 Census DHW Fuels
Figure 188: 1996 Census DHW Fuels
Figure 189: Changes in reported DHW fuel by region
Figure 190: First Class Hotel 1899
Figure 191: 1930s Laundry Copper
Figure 192: Chip heater
Figure 193: Push-through water heater
Figure 194: Low pressure household hot water system (1923)
Figure 195: “An Improved Electrical Water Heater” (1923) NZ Patent 51131
Figure 196: “Domestic Boiler System” (1926) US Patent 1,612,270
Figure 197: 1888 Lighting Fuel Cost Comparison
Figure 198: 1930s ‘Mercer’ Gas Storage Water Heater
Figure 199: 1930s ‘Champion’ Gas Cooker, Water heater & rubbish destructor59
Figure 200: Standing losses as function of tap temperatures
Figure 201: Average daily hot water energy use
Figure 202: Leaking cylinder - only turns off during ripple control
Figure 203: Cylinder that recharges occasionally
Figure 204: Cylinder that rarely turns off
Figure 205: Night-rate hot water cylinder
Figure 206: Example of a vacancy period
Figure 207: Example of a vacancy period for a ‘Night rate’ hot water system
Figure 208: Solid fuel burner output vs rate of change of cylinder temperature
Figure 209: Solid fuel burner output vs rate of change of cylinder temperature
Figure 210: Combined electric and wet-back water heating energy 

Table 87: Gas Hot Water Heating, Location and Income Characteristics
Table 88: Gas Hot Water Heating, Household Size, Composition, Tenure and Life Stage Characteristics
Table 89: Hot water cylinder characteristics by type of hot water heating
Table 90: Annualised Gross Energy Use and Annualised Gross Energy Use for Hot Water
Table 93: Number of Showers by Household Size by Type of Hot Water Heating

Table 131: Hot water cylinder characteristics by type
Table 132 Regional annual hot water energy use by fuel (kWh/house with fuel)
Table 133: Building Regulations 1992 Clause G12 – Objective
Table 134: Building Regulations 1992 Clause G12 – Performance (hot water)
Table 135: NZBC G12/AS1 – Water Temperature & Control (3rd Edition 2006)
Table 136: DHW fuels – international comparison
Table 137: Average DHW energy use by capacity
Table 138: Energy & proportion of main end-uses
Table 139: DHW Fuel use – top and bottom 20% of houses
Table 140: Hot water energy use by number of occupants
Table 141: Electric hot water cylinder standards
Table 142: Electric storage cylinder standing losses by size and grade
Table 143: Total energy consumption and standing losses by HEEP system type
Table 144: Household hot water energy use by system type
Table 145: Comparison gas & non-gas water heater households
Table 146: Regression model for hot water energy use
Table 147: Life stage by water heating fuel
Table 148: Linear model application – non-gas and gas water heating
Table 149: HEEP hot water systems
Table 150: Hot water adequacy by fuel type for randomly selected houses
Table 151: Hot water adequacy by system pressure
Table 152: Wetback use by region
Table 153: Cylinder volume range
Table 154: Hot water systems by fuel source and cylinder volume
Table 155: System pressure by fuel type
Table 156: HEEP random electric and gas cylinder descriptive statistics
Table 157: House and cylinder age comparison
Table 158: Life expectancies of cylinder types
Table 159: Hot water requirements for baths and showers
Table 160: Self reported bathing times
Table 161: Self reported shower duration by time of day per house
Table 162: Shower flow ratings
Table 163: HEEP shower flow by water pressure and temperature
Table 164: Maximum & minimum water flows
Table 165: HEEP Shower warm flow rates by WMCS rating
Table 166: Effect on average flows from retrofitting ‘low flow’ shower heads
Table 167: Auckland water costs (1 Sept 2006)
Table 168: High tap temperatures by system type
Table 169: HEEP 135 and 180 litre cylinder statistics
Table 170: Count of thermostat setting vs tap hot water temperature
Table 171: Tap Temperature and use of tempering valve
Table 172: Count of cylinder grade by house decade of construction
Table 173: Cylinder wrap cost benefit by cylinder grade
Table 174: Some alternative measures for D grade 180 litre retrofit
Table 175: Methods to reduce hot water emissions

Table 187: Average annual hot water energy use per house by fuel

Table 192: NZ Censuses historical summary 1945-2001 – hot water questions
Table 193: NZ Censuses 1945-1996 – text of hot water questions
Table 194: North America – shower water use
Table 195: Australia – shower water usage
Table 196: Perth – shower water use
Table 197: Hot water energy comparison
Table 198: Hot water systems – comparison of properties
Table 199: Wetback heat output percentages

The full report is available for download and viewing online here.