Energy Indicators for Sustainable Development: Guidelines and Methodologies International Atomic Energy Agency United Nations Department of Economic and Social Affairs International Energy Agency Eurostat European Environment Agency

(c) Limitations of the Indicator: When energy use by end use is not known, energy 
use per household can be used as an energy-intensity indicator, but it does not 
measure energy efficiency developments very well. Some important conclusions can 
be drawn, however, if the average winter temperature, ownership of energy-using 
appliances and dwelling size are known. In a country with cold winters and a high 
penetration of central heating systems, a low total use of energy for all purposes, 
relative to total home (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 might imply inefficiencies. However, since energy-use 
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.
The measurement and interpretation of energy intensities are complicated by 
differences among products within a category, such as size (e.g. refrigerator capacity), 
features (freezer compartments in refrigerators) and utilization (hours per year a stove 
is used). 
(d) Alternative Definitions/Indicators: None. 
(e) Measurement of Efficiency: To describe energy efficiency developments, 
intensities should be expressed as energy use per unit of disaggregated energy service. 
The inverse of these intensities would then reflect energy efficiency — for example, 
litres of refrigerated volume at a given temperature divided by electricity use for 
refrigeration, lumens of light per watt of power consumed, or computer tera-flops per 
second divided by power consumption for the computer, etc. In practice, these kinds 
of disaggregated data are not available. For some household equipment, specific 
energy requirements can be calculated from survey data on equipment efficiency and 
usage time per year for the equipment. 
Activity (Services Provided): Ideally, output units would be in energy services 
delivered, such as lumens of lighting, number of meals cooked, area and time heated, 
litres of hot water provided, litres refrigerated, kilograms of clothes washed, etc. In 
practice such data are rarely available, even for individually metered homes. If data 
separating residential energy use by main end use are available, floor area should be 
used as the activity measure for space heating, air conditioning and lighting; number 
of persons per household, for water heating and cooking; and ownership levels 
measured as number of devices per household, for important electric household 
appliances. 

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Disaggregated Intensities: Using the activity measures mentioned above, the 
following intensities may be developed for each main end use: 
• Space heating: energy use per square metre of heated floor area or per square 
metre per degree-day (this intensity should be measured in terms of useful 
energy, i.e. taking into account estimates of the efficiency of different space-
heating alternatives). 
• Energy use per capita for heating water and cooking. 
• Electricity use per unit for each major appliance: refrigerator, freezer, clothes 
washer, clothes dryer, dishwasher, television, etc. 
These specific energy requirements are related to, but not identical to, the inverse of 
energy efficiencies. However, these intensities are often the most disaggregated 
measures that can be constructed from statistics published regularly in Organisation 
for Economic Co-operation and Development (OECD) countries. Yet it should be 
noted that also many countries within the OECD do not estimate the split between 
residential end uses, and consequently even more aggregate measures, such as total 
residential energy per household, remain the only alternative.