Homeowners Professionals

How much does it cost to run a gas fire?

Wondering how much it could cost a month to run your gas fire? Viessmann reveals how you can work this out yourself.

With the cost of living crisis mentioned frequently on our social media feeds and televisions, you may be wondering how you can reduce your energy consumption this winter to save money. If you have a gas fire, you might be concerned about the amount of gas it uses, or perhaps just curious as to how much it costs to run.

We’ve done the calculations and sums for you to give you an idea of exactly how much it costs to run your gas fire. Read on to discover more, and to find out if it's cheaper to use a gas fire or your gas boiler.  

How much gas does a gas fire use?

How much gas your fire uses will depend on a number of factors - how often you use it, how many hours you use it for, etc. However, you can work this out based on the size of the fire.

In the UK, gas fire sizes are generally measured in either kilowatts (kW) or British Thermal Units (BTU) and the amount of energy they consume will be listed as ‘heat input’. This is the figure to look out for if you’re purchasing a new gas fire or you want to know how much gas your existing fire uses.

The heat input is the amount of gas that the appliance uses when it’s on its maximum setting for one hour. For a fire, this is usually between four and six kWs. Therefore, a four kW gas fire will use four kW of energy in one hour, eight kW in two hours, etc. 

To put this in perspective, a gas hob will use around 7.5 kW per hour (if all four hobs are burning at the same time).

Gas fires that are sized in BTU will usually generate between 10,000 and 70,000 BTU to heat a room. It’s important to be aware that larger rooms require a larger fire to be heated properly, so you should calculate the BTU of a room before having a fire installed, to ensure it can keep up with your heat demands. 

A gas fire that generates 40,000 BTU of heat uses approximately 2.83 cubic metres of gas every two and a half hours (or 1.13 cubic metres per hour). This equates to around 12.8 kWh. 

How much does a gas fire cost to run?

Once you know how much gas your fire uses, you can work out how much it will cost to run.

To do this calculation, take the heat input in kilowatt hours (kWh) and multiply this by the amount you pay for gas per kWh. To find this information, you can take a look at your most up-to-date gas bill. The cost used to be around 0.3p per kWh but from October 2022, it could be as high as 0.10p*. 

Using the latter figure, a five kW gas fire would cost around 50 pence to run per hour (five kW multiplied by 10 pence). This amount would then need to be multiplied by the number of hours you run the fire per day/week to get an overall cost. Say, for example, you run the appliance for two hours a day, it would therefore cost you around £30 a month.

You can find a summary of the calculations below:

[Heat input in kW] x [Gas cost per kWh] = [Cost to run per hour]

[Cost to run per hour] x [No. of hours per month] = [Total monthly cost]

For a more accurate reading, you may wish to use your smart meter screen. A smart meter display screen can show you in real-time the amount of energy you’re using (though for gas, it can take up to 30 minutes to update). This means you can switch on your gas fire and see exactly how much it is costing you.

If you’re using your gas fire as well as your gas boiler, you might notice that your energy bill is quite high. It may reduce your energy bill if you turn your fire off when your central heating is on. 

*This figure was correct at the time of publishing but is subject to change.

Is it cheaper to use a gas fire or central heating?

The ultimate question you might want to know the answer to is ‘Will it be cheaper to use my gas fire or my boiler?’. 

A gas fire will be cheaper to use than your central heating, because it is a smaller appliance and uses less gas. Boilers are also sized in kilowatts and so, like the gas fire, a 24 kW boiler will use 24 kW per hour to heat your home and a 42 kW boiler will use 42 kWh to heat your home, for example. 

This is a significant increase on a five kW gas fire. However, you should consider that your boiler is heating your entire home, whereas a gas fire is heating a much smaller space, such as one room. 

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