1.         INDICATOR

(a)        Name:  Intensity of Energy Use in the Residential Sector.

(b)        Brief Definition:  Amount of energy used per person or household in the residential sector.

(c)                Unit of Measurement:  Gigajoules (GJ) per capita or GJ per household.

(d)               Placement in the CSD Indicator Set:  Economic/Consumption and Production Patterns/ Energy Use.  

2.         POLICY RELEVANCE

(a)                Purpose:  The indicator is used to monitor energy consumption in the residential sector.  

(b)               Relevance to Sustainable/Unsustainable Development (theme/sub-theme):  The residential sector is a major consumer of energy with a distinctive pattern of usage. Reducing energy consumption contributes to reducing air pollution and climate change.  Many policies addressing energy efficiency and savings have been formulated for this sector.  In colder countries, for example, the space heating component has been the focus of many energy-saving policies, while in almost all countries, the electric-appliance and lighting component is still the focus of many policies.  

(c)        International Conventions and Agreements:  None specifically for this sector.  

(d)        International Targets/Recommended Standards:  None as such.  However, thermal standards for new homes are in effect in almost all OECD and Eastern European countries, China and some other countries in colder climates.  Efficiency standards for boilers are also important in many countries.  Efficiency standards on new electrical appliances are important in the United States and indirectly in Canada, and voluntary programmes have been important in Japan and Europe.  

(e)        Linkages to Other Indicators:  This indicator is one of a set for energy intensity in different sectors (manufacturing, transportation, commercial/services and residential), with the indicator for energy use per unit of GDP as an aggregate energy intensity indicator.  These indicators are also linked to indicators for total energy consumption, greenhouse gas emissions, and air pollution emissions.  

3.         METHODOLOGICAL DESCRIPTION

(a)                Underlying Definitions and Concepts:  Household or residential energy use encompasses energy used in residential buildings, including urban and rural free-standing houses, apartment dwellings, and most collective dwellings such as dormitories and barracks.  These energy uses typically include cooking, water heating, space heating and cooling, lighting, major appliances for refrigeration, washing and drying, TV and communications, computers, conveniences like food machines, vacuum cleaners, etc., as well as a myriad of small appliances.  Household or residential energy use should exclude energy for farm processes, small businesses or small industry.  The household sector must be separated from the commercial/services sector, although data for many IEA countries did not separate these two sectors in the past.   The energy sources should include not only purchased energy, but also gathered energy such as fuelwood or other biomass and miners’ coal.  

(b)        Measurement Methods:  

·        Energy Use:  Purchased energy for residences/households is usually recorded in the energy statistics of a country with data provided by electric, gas, or heat utilities according to customer definitions that correspond to “households”.  Data on purchases of LPG, other oil products, coal or similar fuels and wood are not always recorded correctly since suppliers may not know where or how these fuels are being used.  

      Alternatively, household/residential energy use can be measured through household surveys. The most direct surveys collect detailed information on both fuels consumed and energy-consuming equipment owned or used.  The most accurate surveys also obtain permission from households to ask energy suppliers for quantities consumed, or they leave fuel-use diaries for households to record what they consume. They measure usage in a variety of appliances and in heating equipment using miniature data loggers. Less detailed surveys estimate the use of each fuel for each major purpose through regression analysis over a large number of households.

      Unit:    Energy is measured in megajoules (mJ) or gigajoules (gJ) (net calorific value).  In most cases, electricity and purchased heat are counted at final or delivered value.  In some cases, primary energy is recorded. (See methodology for manufacturing sector).

·        Residential unit:         Energy consumption is calculated on a per capita or per household basis.  In general, energy consumption depends both on the physical size and characteristics of the dwelling and on the number of people.  As the number of people in a household declines, energy consumption per household declines, while the energy consumption per capita increases.  As a rule of thumb, energy use for water heating, cooking and many appliances tends to vary with the square-root of household size.  

For developing countries with large rural sectors or large numbers of homes without access to electricity, the share of homes in the urban sector and the share in each sector connected to grid electricity is an important factor in total residential energy consumption. The shares of homes using different kinds of biomass fuels are also important. 

(c)        Limitations of the Indicator:  When energy consumption by end-use is not known, energy use per household is a valuable indicator of energy intensity, but it does not measure energy efficiency.  Some important conclusions can be drawn, however, if the average winter temperature, ownership of energy-consuming appliances, and dwelling size are known.  In a country with cold winters and high penetration of central heating systems, a low total consumption of energy for all purposes, relative to total floor area and the severity of winter climate, probably implies efficient heating practices.  Conversely, high energy use relative to floor area in a country with mild winters may imply inefficiencies.  However, since energy consumption habits vary so much, both among countries and among end-uses, few conclusions about “efficiency” can be drawn from the indicator on “residential energy use per household”.  (See alternative definitions/indicators below).  

(d)        Status of the Methodology:  The indicator, with some variations in the methodology, is used in many OECD countries.  It is not widely used in developing countries.  

(e)        Alternative Definitions/Indicators:

·        Measurement of Efficiency:  A true energy efficiency can be expressed as energy use per unit of energy service.  Examples of true energy efficiency would be litres of refrigerated volume at a given temperature divided by electricity use, lumens of light per watt of power consumed, or computer tera-flops per second divided by power consumption.  In practice, these are not measured for large populations.  Specific energy requirements for particular services, taking into account equipment efficiency and the time the service is used, are easier to estimate since these can be summed for a given household and compared with actual consumption.  

·        Output (services provided):  Ideally, output units would be in energy services delivered, such as lumens of lighting, meals cooked, area and time heated, litres of hot water provided, litres refrigerated, kilogrammes of clothes washed, etc.  In practice, such data are rarely available, even for individually metered homes.  A suitable proxy for each service may be either the area heated (or lit), the number of people in the household receiving meals or hot water, and the average number of appliances, by type, per household or per capita.  

·        Energy requirements:  If both energy use and equipment ownership for each major service is known, then specific energy requirements can be developed as follows:  

-     Space heating: energy use per sq. meter heated or per sq. meter per degree day;

-     Energy use per capita for water heating and cooking; and

-     Energy use per year for each major appliance: refrigerator, freezer, clothes washer, dryer, dishwasher, TV, etc.  

These specific energy requirements are related to, but not identical to, energy efficiencies.  They differ in that they do not measure accurately the service provided, since, for example, a large refrigerator gives more service than a smaller one. 

5.         ASSESSMENT OF DATA  

(a)        Data Needed to Compile the Indicator:   

(i)      Energy use in the residential sector (as indicated in section 3(b) above);  

(ii)    Number of households and/or population.  

(b)        National and International Data Availability and Sources:  Until the early 1980s, the residential or household sector was not well distinguished from the commercial/service sector in a majority of OECD member country energy statistics, particularly for liquid and solid fuels.  In OECD countries, this distinction is now common.  In developing countries, data often distinguish residential and commercial consumption of electricity and natural gas, but users of liquid and solid fuels are often not accurately identified.  Many national energy balances thus fail to distinguish between the residential and commercial/service sectors.  Such problems are indicated when data show electricity and natural gas consumption for both the residential and commercial/service sectors, while liquid and solid fuel consumption is shown for only one of the two sectors.  

The other major challenge is to estimate the use of biomass fuels of all kinds in developing countries.  This is important in almost all developing countries, even in urban areas.  

Because of these two problems, aggregate national or international statistics must be used with caution.  

Data on equipment are usually developed by electric and gas utilities, as well as by trade associations representing electric and gas appliance manufacturers.  These have generally not been compiled in an internationally compatible form.  No single agency collects all the data, except in a few IEA countries (United States, France, Netherlands) where detailed household surveys are undertaken.  The World Bank has sponsored many one-time household surveys in developing countries, focusing either on rural or urban areas.  As noted above, national or private energy companies often undertake marketing surveys.  Oil industry sources in most IEA countries often compile data on oil-equipment sales and ownership.  

(c)        Data References:  

IEA:     Energy Balances of Member countries.

            Energy Statistics of non-Member countries.  

5.         AGENCIES INVOLVED IN THE DEVELOPMENT OF THE INDICATOR  

(a)                Lead Agency:  The lead agency is the International Energy Agency (IEA).  

(b)               Other Contributing Organizations:  None. 

6.         REFERENCES  

(a)        Readings:  

Schipper, L., Ketoff, A., and Kahane, A. “Estimating Residential Energy Use from Bottom-Up, International Comparisons. Ann. Rev. Energy 10. Palo Alto CA: Ann. Revs., Inc. 1985.  

(b)        Internet sites:  

International Energy Agency:  http://www.iea.org  

World Bank:  http://www.worldbank.org/html/fpd/energy/