CALORIFIC VALUES
USED IN THE COMPUTATION OF
COMPARATIVE DOMESTIC HEATING COSTS

The data shown in the following table was sourced from an official website - it may not be up-to-date. If the data is important to the reader, confirmation should be sought from an authoritative source (but from experience you will find your fuel suppliers will not be that source). In order to compare heating costs one has to know the unit- (as indicated in the table) cost for the fuel/s concerned. In order to make a comparison the efficiency rating of the appliance has also to be known. For example, one kilowatt (kWh) of electricity may cost more than one kWh of mains gas, but will not normally be operating at 100% efficiency which gas is not capable of. Older equipment and even the most efficient which are operating at less than maximum settings (non-electrical equipment) is likely to decrease the efficiency further. The apparent 'face value' of fuels can be very misleading. Your appliance manufacturer or supplier should be able to advise you of efficiency ratings - make sure they are for all heat settings that your appliance can be set to and other fitting considerations.

In order to make a calculation one takes the fuel supplier/s 'published' unit cost divided by the heat content and adjust for appliance efficiency at various settings. Although the 'published' cost per kWh may be cheaper, the real cost may be greatly different after allowing for appliance efficiency. Solid fuel, in particular, can be very inefficient where heat is allowed to freely rise up the chimney. Bear in mind that appliance manufacturer's efficiency ratings are calculated in test conditions and not normally 'on site'. Like many advertised car fuel consumption figures, these can be 'optimistic'.

Although these data are UK based they are likely to be exactly, or very near the same, elsewhere.