SR122 Energy use in NZ households - report on year 7 of the Household Energy End-Use Project (HEEP) (2007)

This report covers the activities of the 7th full year of the Household Energy End-Use Project (HEEP) and is based on survey, house audit and monitored energy and temperature data from 200 randomly selected houses in Auckland, Hamilton, Wellington and Christchurch and on survey data in these houses, plus additional non-random houses. Monitoring will be completed in early 2005.

Analysis includes examination of energy by end use, indoor temperatures, space heating energy use, seasonal mortality, hot-water energy use, hot-water temperatures, shower flows and hot-water system standing losses.

The top four uses of electricity and natural gas are hot water (29%), space heating (22%), lighting (11%) and refrigeration (10%). Houses built after 1978 (mandatory thermal insulation requirements) are found to be on average 1°C warmer with that same energy use. Winter evening temperatures in pre-1978 houses average 17°C in the living room and 14°C in the bedroom. There is a wide range of space heating energy use, but houses heated by solid fuel tend to have warmer temperatures than houses heated by electricity, natural gas or LPG. More than 40% of the hot water was delivered at unsafe temperatures (over 60°C).

The average shower flow for a low-pressure hot-water system is 7.2 litres/minute and for a mains pressure system is 10.6 litres/minute – with increasing numbers of mains pressure systems being installed. Average hot-water system standing losses range from 24% (natural gas storage) to 36% (electric night rate storage) of the total energy use.