How Much Does Gas Central Heating Cost Per Hour?

The basic calculation

Gas central heating is billed by the kilowatt-hour (kWh) of gas you burn, not by the heat you get out. So the headline formula is straightforward:

The key number people get wrong is the boiler's input. The figure printed large on a combi — say "30kW" or "35kW" — is usually its central heating or hot water output. The gas input (the energy it actually draws from the meter) is a little higher, because no boiler is 100% efficient.

A modern A-rated condensing boiler runs at roughly 90% efficiency, so a boiler putting out 24kW of heat is pulling in around 26–27kW of gas.

You'll find the input rating on the data badge inside the casing or in the manual, usually written as "Qn" in kW (note this is often quoted as a net figure; UK gas is billed on a gross basis, which is a little higher, so the truest guide is always your own meter — see the tip below).

Why this is an upper estimate, not your real bill

Here's the part the simple formula hides: your boiler almost never runs at full input. Modern combi and system boilers modulate — they throttle the flame up and down to match demand. Once your home reaches temperature, the boiler drops to a fraction of its maximum and cycles on and off.

So a "30kW" boiler does not burn 30kW of gas for every hour the heating is on. Over a typical winter hour it might average a third to a half of its rated input. Treat the full-input sum as a worst-case ceiling — your actual cost per hour is usually well below it.

The current price cap (2026)

Under the Ofgem energy price cap for 1 July to 30 September 2026, the typical figures for a Great Britain household paying by Direct Debit are:

Fuel	Unit rate (per kWh)	Standing charge (per day)
Gas	7.33p	29.04p
Electricity	26.11p	57.19p

A worked example

Let's price a standard combi boiler with a gross gas input of around 26kW, using the 7.33p/kWh gas rate above:

Scenario	Gas used	Cost (at 7.33p/kWh)
Full input, one hour (worst case)	26 kWh	≈ £1.91
Modulating at ~50% over the hour	13 kWh	≈ £0.95
Modulating at ~33% over the hour	~8.6 kWh	≈ £0.63

So the same boiler can cost anywhere from roughly 63p to £1.91 an hour depending on how hard it's working — and on a mild day, when it's just topping up the warmth, you'll sit near the bottom of that range.

From "per hour" to a monthly and annual bill

Most people searching for an hourly figure really want to know what it means for the bill. Here's the same 26kW boiler scaled up, assuming it modulates to roughly half its input over the hours it runs (a reasonable real-world average) at 7.33p/kWh.

These are indicative heating-only estimates, last checked 2026 — your home, insulation and weather will move them:

Period	Assumption	Indicative gas cost
One hour	~13 kWh (half input)	≈ £0.95
One day (winter)	~8 hours of heating	≈ £7.60 + 29p standing charge ≈ £7.90
One month (mid-winter)	~30 days	≈ £230–£240 incl. standing charge
One year (heating only)	~7 colder months, tailing off in summer	often in the region of £600–£900

Two things to keep in mind. First, the daily standing charge (about 29p/day, roughly £106 a year for gas) is payable whether or not the heating is on — it's a fixed cost on top of the per-kWh figures.

Second, your annual bill also includes hot water and any gas cooking, so the whole-home gas figure will be higher than the heating-only estimate above. To price your own boiler, swap in your gross input rating and your real unit rate in the calculator below.

Cost-per-hour calculator

Plug in your boiler's gross gas input, how long the heating runs, your unit rate and a rough modulation level. Everything runs in your browser — nothing is sent anywhere. Defaults use the July 2026 cap gas rate (7.33p/kWh).

Cost per hour by home size

People often ask the question by house size — "what does it cost to run the heating in a 3-bed semi?" The honest answer is that the property does not change the price per kWh; it changes the boiler people tend to fit and how many kWh that boiler burns.

As a rough guide, here are typical combi sizes and an indicative hourly range at the 7.33p/kWh cap rate, allowing for modulation between about a third and full input:

Home	Typical combi output	Approx. gross input	Indicative cost per hour*
Small flat / 1-bed	24–25 kW	~26 kW	≈ 35p – 95p
3-bed semi	28–30 kW	~31 kW	≈ 45p – £1.15
4-bed detached	32–35 kW	~37 kW	≈ 55p – £1.35
5-bed / larger	35–42 kW	~44 kW	≈ 65p – £1.60

*Indicative ranges, last checked 2026, at 7.33p/kWh. The lower end assumes the boiler modulates to about a third of input; the upper end is full input (rarely sustained for a whole hour). Combi sizes are usually driven by hot-water demand, not house size, so treat these as a starting point, not a rule.

Gas vs electric (and oil/LPG) running costs

If you're weighing up how you heat your home, the headline is that gas is far cheaper per unit of energy than electricity. Under the July 2026 cap, gas is about 7.33p/kWh against roughly 26.11p/kWh for electricity — so a like-for-like kilowatt-hour of electric heating (a panel heater or immersion) costs around 3.5 times more than gas.

The important exception is the heat pump. Because a heat pump moves heat rather than burning fuel, it delivers roughly 3kWh of heat for every 1kWh of electricity it draws (a "coefficient of performance" of around 3).

That efficiency narrows the gap dramatically, which is why a well-installed heat pump can be competitive with, or cheaper than, gas to run despite electricity's higher unit price.

For homes off the mains gas grid, heating oil and LPG are the usual alternatives. Their prices aren't set by the Ofgem cap — they track wholesale markets and you buy them in bulk — but as a rough guide oil tends to sit a little above mains gas per kWh, and LPG is typically dearer still.

If you're off-grid, the Boiler Upgrade Scheme is especially worth a look (see below).

A common misunderstanding is that the unit rate itself scales with the size of your home — that a five-bed house somehow pays a higher pence-per-kWh than a flat. It doesn't. The unit rate is set by your tariff and the price cap, not by your property. A mansion and a studio on the same tariff pay the identical price per kWh of gas.

What does change with size is the number of kWh you burn. A larger, draughtier, poorly insulated home loses heat faster, so the boiler runs longer and harder to hold temperature — more kWh, same price each.

That's why insulation, draught-proofing, thermostat settings and how long the heating is on matter far more to your bill than the boiler's badge rating. A well-insulated large home can easily cost less to heat per hour than a cold, leaky smaller one.

Cutting the cost per hour

These are the levers that genuinely move the figure your calculator above produces. The savings percentages below come from UK research and the Energy Saving Trust; treat the cash figures as indicative (last checked 2026) since they scale with your own usage and the cap.

• Turn the room thermostat down a degree. The Energy Saving Trust estimates that turning your thermostat down by just 1°C can cut your heating bill by around 10% — on the order of £90 a year in a typical home. Aim for the lowest comfortable setting (often 18–21°C).
• Set the flow temperature correctly. On many combis the central-heating flow temperature is shipped too high (around 75–80°C). Lowering it to about 60°C or below keeps the boiler condensing properly; research (cited by the Energy Saving Trust and from the Salford Energy House study) found this can cut gas use by up to roughly 9%. This is a control-panel setting you can adjust yourself — see our guide to boiler flow temperature.
• Use the thermostat and programmer, not the boiler dial. Heating to a sensible room temperature for the hours you're actually home is the single biggest lever, and the only one that directly cuts the "hours run" in the formula.
• Bleed cold radiators and keep system pressure in range (typically 1–1.5 bar cold, rising to about 2 bar when hot). Both are homeowner-safe jobs that help the system run efficiently.
• Insulate and draught-proof. Fewer kWh lost means fewer kWh bought — and it's the kWh, not the unit rate, that a bigger home racks up.
• Consider a heat pump. If you're thinking about replacing an ageing boiler, the government's Boiler Upgrade Scheme offers £7,500 off the cost of installing an air-source or ground-source heat pump in England and Wales (with a higher £9,000 uplift available for eligible off-grid oil or LPG homes from 21 July 2026). It's a live scheme — your MCS-certified installer applies on your behalf — so check your eligibility before assuming gas is your only option. See our Boiler Upgrade Scheme guide.

One safety note: anything beyond the basics above — the gas valve, pipework, flue, sealed circuit, pressure relief valve or removing the casing — is strictly for a Gas Safe registered engineer. Never attempt gas work yourself, and always check an engineer's registration at gassaferegister.co.uk.

If you ever smell gas, leave the property and call the emergency line on 0800 111 999.

Where boiler cover fits in

Knowing your running cost is one half of budgeting; the other is what happens when the boiler breaks down.

A failed pump, a leaking heat exchanger or a faulty PCB can mean a sizeable repair bill on top of your day-to-day gas. Boiler cover spreads that risk into a fixed monthly cost, with repairs carried out by registered engineers.

Whether it's right for you depends on your boiler's age and your appetite for risk — our guide on whether boiler cover is worth it walks through the maths. When you're ready, you can compare boiler cover from a selected panel of providers and weigh up the options side by side.

This article is general information, not financial or technical advice. Figures are indicative 2026 GBP estimates and depend on your tariff, boiler and usage. We compare a selected panel of providers, not the whole market, and may earn a commission. Always use a Gas Safe registered engineer for gas work.