When checking a gas fire it is important to know how to convert between kW net and kW gross heat inputs. Manufacturers of gas fires sold in Europe must have the appliance CE approved. To comply this approval process the appliance must be fitted with a Data Plate. This data plate shows the various settings for the fire like gas type, gas category, CE pin number and Heat Input. It will also have information like the manufacturers name and address.

The heat input is the measure of the amount of gas that is being used by the gas fire when it is on full. Do not confuse this with heat output which is the heat supplied to the room by the gas fire and is dependent on the efficiency of the appliance. Read our guide to fireplace efficiency.

The heat input will be shown on the data plate in kilowatt (kW). There are two forms of kilowatt, net and gross. Check the data plate older appliances will most likely show kW gross, modern appliance will show it in kW net.

To convert from kW gross to kW net
heat input (net) = heat input (gross) ÷ 1.1

For example a 10kW (gross) appliance will be rated at 9.1kW.

To convert from kW net to kW gross
heat input (gross) = heat input (net) x 1.1

For example a 9.1kW (net) appliance will be rated at 10kW.

When installing or servicing a gas fire the gas engineer must use the manufacturers instructions and refer to the data plate to identify the appliance correctly. If either the data plate or install booklet is missing the gas fire should be disconnected from the gas supply until it can be identified correctly. Contact the manufacturer to see if they can trace the fire.

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