HEEP reveals national household energy uses
This is a part of the
Energy efficiency
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The soon to be released HEEP Year 10 report provides some new knowledge about New Zealand dwellings and how they use energy.
November 2005 was a key milestone for the Household Energy End-use Project (HEEP). Data collection was completed providing the first data set of actual energy use for an entire sector in any country in the world.
HEEP started in 1995 with a pilot study to develop the necessary monitoring and survey methods. A total of about 400 randomly selected houses have been monitored, covering New Zealand from Invercargill in the south to Kaikohe in the north. Of these, 350 houses were monitored in the last four years of the project. The 440 hot water cylinders, 65 wetbacks, 206 solid-fuel burners, 7 solid-fuel ranges, 42 open fires and 175 portable LPG heaters provide a unique snapshot of New Zealanders in their homes.
Breaking down energy use
HEEP is now able to provide a full breakdown of New Zealand household energy consumption by fuel type and end-use (see Figure 1). Electricity use accounts for 69% of total residential national fuel use, followed by solid fuel at 20%, reticulated gas at 9% and bottled LPG at 2%. Oil is used in a very small number of houses. The breakdown by location varies hugely depending on the types of fuels that are used in houses, particularly for space heating.
The breakdown of end-use shows the largest portion of energy is used for space heating (34%). This is followed by hot water at 29%, and around 10% each for refrigeration, other appliances, lighting, and range (see Figure 2). Again this breakdown varies by location, with less space heating in warm climates and more in colder climates where it can be up to 70% of household energy use.
Some heating doesn’t keep us warm
When looking at space heating, it is important to take into account the efficiency of the appliance (see Figure 3). In terms of the heating energy delivered to the house, the most important space heating fuel is solid fuel (mainly wood) which makes up about 45%, followed by electricity at 32%, reticulated gas at 15% and LPG at 8%.
HEEP monitoring found that houses heated by open fires, portable electric and LPG heaters are the coolest, while houses with central heating or enclosed solid-fuel burners are warmest.
The cool temperatures found in the living rooms of homes heated with LPG heaters was unexpected. Analysis of the data found that even though portable LPG heaters can produce a lot of heat, most were used sparingly, if at all. About 30% of the portable LPG heaters were not used during the winter, while just under half (48%) were only ever used at the low setting which is equivalent to a 1 bar electric heater.
Newer homes warmer all year
Other results from HEEP have been both expected, and unexpected. The importance of thermal insulation in creating warmer winter temperatures was identified in early HEEP reports. We have now started to examine indoor temperatures throughout the year, and interestingly have found that newer (post-1978) houses also appear to be warmer in summer than older houses. Although thermal insulation became mandatory in 1978, there have been many other changes in design styles, construction and the use of materials over that time. Given the likelihood of ever-warmer summer temperatures, the reasons for this are being further investigated.
Baseload more than heating
The HEEP data has supported the first nationwide statistically representative study of standby and baseload electricity use for any country. The baseload of a house is the typical lowest power consumption when everything that is usually switched off is off – on average 112 (±4) W. This is, coincidentally, about the same power consumption as electric space heating, at 105 (±21) W. Who would have thought that all those little lights and background appliances were using more electricity than space heating?
Standby power consumption was estimated at 57 (±4) W, heated towel rail use at 21 (±2) W, and faulty refrigeration appliances (compressors always on) at 15 (±10) W. Some appliances with standby, and some small continuous loads that are known to be excluded, make up another 11 (±4) W, leaving 8 (±12) W unaccounted for. This represents a very nearly complete inventory of standby power consumption for New Zealand houses. It is unlikely that any major standby appliances are left unaccounted for.
HEERA model developed
The original goal of developing an energy model of the residential sector is well on the way. Statistical analysis tools have been used to develop the equations (or ‘algorithms’), and with our research partner, CRL Energy, these have been turned into the Household Energy End-use Resource Assessment (HEERA) model. An early version of HEERA has already been used to support national and regional analysis of energy efficiency and the electricity system.
Widespread interest in results
There has been sizable national and international interest in the HEEP research, with 4,700 copies of ‘Executive summaries’ downloaded from the BRANZ website in the past year – a 50% increase over the previous year. Some 360 copies of the 139 page Year 9 report were downloaded by people in 22 countries from Australia to the United Arab Emirates, although most copies have gone to New Zealand (65%).
Results from the HEEP research are already in wide use by Government, industry and academia. They have started to change the way we think about the hows, whys, wheres and whens of energy use in New Zealand homes.
HEEP changing energy statistics
The HEEP Year 9 report suggested that the Ministry of Economic Development’s Energy Data File (New Zealand’s official energy statistics) was underestimating the use of wood in houses. The January 2006 edition (available for free from www.med.govt.nz) agreed, and increased the reported use of wood by 5.6 PJ – a 9% increase in residential sector energy use. If this heat was provided by electricity using current technology, it would be equal to a new power station half the size of the current Huntly power station, and would put a major strain on many electricity distribution networks.
The revised estimate of solid fuel use in the residential sector has critical implications for assumptions relating to the services it provides. Although solid fuel is mainly used for space heating, it also provides about 5% of all hot water energy consumption.
HEEP’s future
HEEP’s main funding will terminate mid-2007, and there will be a final Year 11 report. Analysis is well in hand to ensure the major benefits from the HEEP data will be of real value to the building industry and other interested users. The HEEP data will continue to be available for specialised analysis, on request. It is likely that the methods developed by HEEP will form the basis for a future proposal for new research into the built environment.
For more
Once it is released later this year, the HEEP Year 10 executive summary will be available on the BRANZ website at www.branz.co.nz and the full report on sale through the BRANZ bookshop.Major funding for this work has come from the Foundation for Research, Science and Technology, and Building Research. Other funders include EECA, Transpower, Ministry of Social Development and Fisher & Paykel Ltd.
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Articles are correct at the time of publication but may have since become outdated.
