On the first page are two coloured charts, one representing the energy efficiency of the dwelling
(a flat, maisonette, bungalow or house) and the other the environmental impact of heating, lighting
and providing hot water in the dwelling.
On both charts the dwelling is rated from 1 (worst) to 100 (best) and put into one of seven bands G (worst)
to A (best). There are two ratings on each chart: the current rating and the potential
rating if a number of recommendations are followed.
The energy efficiency of a dwelling is a measure of how well insulated are its floors, walls,
windows and roof. A perfectly insulated house (with a rating of 100) should not lose any heat, so should only need
energy to heat up from cold and to replenish losses from opening doors and windows. The worst insulated house (with
a rating of 1) is akin to a draughty tent.
The environmental impact of a dwelling is based on a measure of the carbon dioxide
emissions in providing heating, lighting and hot water. For example solar systems produce no carbon dioxide, so
have zero environmental impact (when operating) and would attract a perfect high rating (100). A condensing gas
boiler with over 90% efficiency would attract a high rating, but is still producing carbon dioxide as a by-product of buring
natural gas. However a 30 year old oil or gas boiler with an originally low efficiency (say 60%) will have declined
further in efficiency over the years and is likely to produce a very low rating.
Also on the first page are calculated costs of heating, lighting and hot water for the
dwelling based on a series of assumptions that are consistent across the country. This enables houses in the same location
or in opposite areas of the country to be directly compared. It is unlikely that the calculated costs will be the
same as the actual fuel costs as different occupants of the same house can have completely different patterns
of usage. For example a family of four in a 3 bedroom house might have two showers, a bath and two washing machine loads
every day, and the heating switched on during the day, whereas a single person in the same house is likely to have a
fraction of that usage.
The rest of the Energy Performance Certificate has a number of recommendations
grouped according to their cost which if implemented would improve the energy efficiency and/or environmental impact of the
dwelling. The approximate savings to be gained from following the recommendations are also given, which enables an approximate
payback to be calculated for each improvement.
