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How Much Gas Does A Boiler Use Per Hour?

how much gas

If you are feeling the effects of a spike in your energy bills, or you are considering alternative options from a gas-fuelled boiler, then one of the main things you will need to know as a homeowner is how much gas your boiler typically uses. 

A number of factors feed into how much is used, but a good way of telling is simply by looking at the kWh of your boiler and its efficiency rating.

Using kWh to work out your gas usage

The best way to measure gas consumption is to use kilowatt-hours (kWh), the standard unit of measurement. A typical low-consuming household’s annual use is around 8,000kWh, 12,000kWh for moderate consumption, and 17,000kWh for heavy-consuming homes per year. 

That puts a typical household’s monthly gas usage at around 1,000 kWh (a kWh representing the energy required to run a 1,000-watt appliance for one hour, so 1 KW is 1,000 watts). 

However, your residential gas use typically includes gas boilers, cooking, and other purposes. This means that when you are trying to calculate the exact gas usage of your boiler, it is not always clear where that gas has been consumed.

Types of Household Gas consumption (kWh)
Low consumption 8,000
Moderata consumption 12,000
Heavy consumption 17,000

How Much Gas Does A 30 kW Boiler Use Per Hour?

A 30-kilowatt boiler consumes 30 kilowatt-hours worth of gas. If your 30kW boiler runs for five hours a day, your daily consumption should be roughly 150 kWh. With a current average price of 32.42 pence per kWh in Great Britain that amounts to roughly £1.62.

In winter the average home is heated for approximately 8.7 hours a day, resulting in an average daily expenditure of £2.82 at an annual cost of £1029.50 for a 30kW boiler.

Average cost per day of running a 30kW boiler.

kW No. Of
kWh p/kWh cost
per day
30 5 150 32.42 £1.62
30 8.7 261 32.42 £2.82

Calculating your Average Monthly Energy Bill

Can be difficult due to various factors such as different consumption habits, where you live, your usage, and even how you pay for your energy. 

If your fixed-rate agreement has expired or you have just transferred home, you will be subject to a basic variable rate tariff (SVR). The table below illustrates the average energy bill for customers on a basic tariff.

The amount of gas boiler fuel consumed is influenced by factors, such as the type of boiler, the age and condition of the boiler, the efficiency rating, and how large your home is in relation to the boiler. Therefore, it’s best to calculate the amount of energy consumed to heat your home in kWhs.

How much does it cost to run gas central heating per hour UK?

The figures quoted below are taken from and apply to the period starting 1st January 2023 up to 31st march 2023.

If you use mains gas, you’ll pay roughly 9.84p per kilowatt-hour. This means that if you have a 35 kW boiler, it will cost you around £3.44 to run it for an hour.

The cost of running an LPG boiler is around 7.6p per kilowatt-hour. So, you have to pay roughly £2.66 per hour to run a 35 kW LPG combi boiler.

Average cost per hour of running a 35kW boiler.

Fuel kW No.
kWh p/
Gas 35 1 35 9.84 £3.44
LPG 35 1 35 7.6 £2.66
Average Daily Cost of running 35kW Boiler using Gas and LPG as fuel

Why is my boiler using so much gas?

If your boiler uses more gas than it should, check with your provider to ensure that their prices haven’t increased. If they haven’t, here are a few more reasons why you might be consuming more.

1. Using an older boiler

After a few years of service, the boiler’s efficiency degrades. New gas boilers can be up to 96% efficient but typically sit around 85-92%. However, boilers over ten years old can lose up to 30% of their efficiency. Which is typically why we suggest getting a new boiler fitted after 10 years. 

 This means that if you have a 35 kWh boiler which is 85% efficient, you will need to use 40.25 kW to get 35 kW energy usage for your property as the other 15% (5.25) is lost. Moreover, to calculate the cost of running an older boiler that is 30% less efficient. This would result in an additional 10.5 kWh of gas consumption for your old boiler, for a total of 45.5 kWh.

2. Malfunctioning programmer or thermostat

Your boiler should stay off when it has already reached its pre-programmed temperature. A faulty thermostat or programmer may cause your boiler to operate indefinitely, burning more gas. 

Check to see if you have the proper timings and temperatures set. Observe your boiler for any indications that it turns on even though the thermostat or programmer is turned off. To resolve the issue, you may need to contact a boiler engineer.

3. Broken motorised valve

The flow of hot water from the boiler into a cylinder or the radiators is controlled by a motorised valve. The valve opens to allow hot water to flow when the boiler is turned on and then closes to halt the flow when it’s off. 

However, this valve could fail or become jammed. This will cause your radiators to continue to heat up even when they don’t need to. Check to see if the manufacturer’s warranty is still in effect. Ensure that your valve is inspected and changed by qualified technicians.

How much gas does a pilot light use?

Boilers under 15 years old use electronic ignition and do not have pilot lights. On the other hand, older boilers feature a pilot light that fires continuously and consumes roughly 1,500kWh or more per year. 

A pilot light is used to start the main burner when the boiler is turned on, it remains lit. If your boiler has a pilot light, consider upgrading to a more energy-efficient one. This could save you money on the gas used to power a pilot light.

How many hours a day should heating be on?

The length of time your heater runs will be determined by how well your home is insulated. In the winter, centrally heated homes in the UK are heated for approximately 8.7  hours a day. However, the majority of homeowners start heating their homes daily from October to March or April. Therefore, the heating season is expected to last approximately 5.6 months.

In conclusion, trying to figure out how much gas your boiler is using per hour is like trying to solve a complicated math equation. But fear not, with a little bit of knowledge about kilowatt-hours (kWh) and some basic calculations, you’ll be able to figure out your boiler’s gas consumption in no time.

A 30 kW boiler may seem like a heavy drinker at first, but when you factor in the daily run time and the cost of gas, it’s actually quite moderate. The real gas guzzlers are the older boilers, they may have served you well in the past, but they’re like that old car that keeps breaking down and costing you a fortune in repairs. 

So, if your boiler is using more gas than it should, maybe it’s time for an upgrade. Don’t let a faulty boiler burn a hole in your pocket.

Eddie Scoffin

Boiler Choice Director & Founder

This blog was written in collaboration with Eddie Scoffin, the founder of Boiler Choice. Eddie has been installing boilers for over a decade. With a passion for excellence and customer satisfaction, Eddie’s leadership and expertise have been instrumental in the success of Boiler Choice. His commitment to making the boiler installation process hassle-free for customers has earned him a respected reputation in the industry.

Updated on April 28, 2023