Flame effect gas fire..

Owain_Moneysaver

Depends on the gas fire. Some are only 50% efficient so half the money is effectively going up the chimney. Say 4 kw consumption, for 2 kW heat in the lounge. (and for all the hot air that goes up the chimney, cold combustion air has to be drawn from outside into the lounge.)

A modern condensing gas boiler will be around 90% efficient, and will modulate its output as required. Say 20kw max, modulates down to 50% so 10kW actual consumption, 90% efficiency so 9kw output and heats the entire house. In this example the fire costs half as much to run per hour than the boiler. But the boiler heats maybe the whole house - 4 or 5 rooms?

Heating only the lounge, some of the heat will be lost through the internal walls and doors to the other colder rooms.

If you turn down the radiator valves in the rooms you don't want heated or even better get the bedroom rads on a separate zone with their own programmer, you can cut the boiler consumption right down.

tanith

Thankyou all thats given me something to think about....I'm off to put it on for an hour or two..

ollski

A decorative fuel effect gas fire ie directly under a flue and with a nice 100cm2 vent is 15 - 20% efficient and often in excess of 7 kw wheras many new lfe fires are 70% plus efficiency and 4kw o you have a whole range of figures to choose from.

Ben84

Another aspect that should also be mentioned about open fires, whatever fuel you're burning in them, is that they vent a lot of air up the chimney (taking much of their energy output with them), but also if you're using some kind of central heating that is going up the chimney too and being replaced with cold air drawn in from outside. It might seem surprising, but the net efficiency of an open fire can be close to zero or negative when you're using central heating at the same time. Of course it creates a warmer space around the fire, but the rest of the house suffers and your boiler is burning more gas to make up for the greatly increased air loss.