Heat pump vs gas: the honest UK numbers

Last verified: 14 September 2026. Energy figures are a quarterly snapshot - see the dated notes below before relying on any specific number.

Almost every “heat pump vs gas” page online is trying to sell you something - an installer wants the job, a manufacturer wants the unit, a comparison site wants your details. So the numbers get nudged. The heat pump always wins, the savings are always large, and the awkward cases never get mentioned.

This page does it differently. We work through the actual arithmetic with current UK figures, show every assumption, and tell you plainly where a gas boiler still makes more sense. We don’t sell heat pumps, take installer commission, or capture your details. If the honest answer for your home is “stick with gas for now,” we’ll say so.

The short version: for a reasonably insulated home with a well-designed install, a heat pump runs a little cheaper than gas - and the gap widens if you add the right tariff. But “well-designed” is carrying a lot of weight in that sentence, and the headline savings figures you see elsewhere usually assume a best case that not every home achieves.

The one number that decides everything

Heating cost comparisons live and die on a single ratio: how much you pay per unit of useful heat, not per unit of energy bought.

A gas boiler buys gas and burns it. A modern condensing boiler turns roughly 90% of that gas into useful heat - the rest goes up the flue. So your real cost per unit of heat is the gas unit rate divided by 0.90.

A heat pump buys electricity and moves heat rather than burning anything. For every unit of electricity it draws, it delivers several units of heat. That multiplier is the SCOP (Seasonal Coefficient of Performance) - the average efficiency across a whole heating season, cold snaps and mild spells included. A SCOP of 3.5 means 3.5 units of heat per unit of electricity. So your real cost per unit of heat is the electricity unit rate divided by the SCOP.

Everything else in this article is detail hanging off those two calculations.

The current price-cap numbers

Electricity costs much more per unit than gas in the UK - that’s the central difficulty for heat pumps, and it’s why efficiency matters so much. Under the Ofgem price cap for 1 October 2026 to 31 December 2026 (national average, direct debit, as published):

• Electricity: 26.32p per kWh
• Gas: 7.97p per kWh

Source: Ofgem, energy price cap unit rates and standing charges.

Electricity is about 3.3 times the price of gas per unit. That ratio is the hurdle a heat pump’s efficiency has to clear. If a heat pump is more than 3.3 times as efficient as your boiler at turning energy into heat, it wins on running cost. If it’s less, gas wins.

Two caveats worth holding in mind. First, these are national-average figures - actual unit rates vary across the 14 regional cap areas, so your own bill will differ. Second, these are the capped variable rates; both gas and electricity can be bought cheaper on a fixed or specialist tariff, and as we’ll see, the right electricity tariff changes the heat pump answer materially.

Working the numbers

Let’s do the cost-per-unit-of-heat calculation directly.

Gas boiler, 90% efficient:
7.97p ÷ 0.90 = 8.9p per kWh of heat

Heat pump at SCOP 3.5 (a realistic, well-installed figure):
26.32p ÷ 3.5 = 7.5p per kWh of heat

On those figures the heat pump is cheaper per unit of heat - about 15% less. That’s running off the standard variable electricity rate with no special tariff.

The break-even point is a SCOP of 2.97. Above it the heat pump is cheaper to run than the boiler; below it, the boiler wins. Watch how sensitive the answer is:

This single table is the honest heart of the whole debate. A heat pump that achieves SCOP 4.0+ is comfortably cheaper to run than gas. One that struggles along at SCOP 2.5 - because it’s running hot flow temperatures into undersized radiators in a draughty house - is meaningfully more expensive than the boiler it replaced. Same technology, opposite verdict, and the difference is almost entirely about the quality of the design and install.

What actually determines your SCOP

Because the SCOP is the whole game, it’s worth knowing what moves it. The single biggest lever is flow temperature - how hot the water is that the heat pump sends to your radiators or underfloor pipes. A heat pump running at 35°C flow can reach SCOP 5.0 or more; the same unit forced to run at 55°C flow to keep up with small radiators drops to around 2.5–3.0. That’s 25–40% more electricity for the same warmth.

Keeping flow temperature low is what insulation, correctly sized radiators, and weather compensation are all really for. They’re not separate nice-to-haves - they’re the things that let the heat pump run efficiently. This is why a heat pump in a well-insulated home with a thoughtful installer behaves completely differently from the same unit bolted onto a cold house by someone leaving the controls on factory defaults.

For context on what’s achievable: the best air source units on the market quote SCOP figures above 5.0 at 35°C flow in laboratory conditions. Real-world seasonal performance is usually lower than the lab figure, and a sensible planning assumption for a good install in a decently insulated UK home is SCOP 3.5–4.5. We’d treat anything quoted much above that with caution unless your home is genuinely well suited (low flow temperatures, generous emitters, good insulation).

The tariff that changes the maths

So far we’ve used the standard price-cap electricity rate. But heat pump owners don’t have to. Specialist heat pump tariffs price electricity well below the cap for part or all of the day, and they tilt the comparison firmly in the heat pump’s favour.

The mechanism is simple: if you can run the heat pump (and ideally pre-warm the house or a buffer) during cheaper hours, your effective electricity rate falls, which lowers your cost-per-unit-of-heat regardless of SCOP. A heat pump on a well-chosen tariff can close, or more than close, the running-cost gap with gas even at a middling SCOP.

We’re deliberately not quoting a specific tariff rate here, because these change frequently and we only publish numbers we can stand behind on the day. The honest, durable point is this: the heat pump’s running-cost case is strongest when paired with a heat-pump-specific electricity tariff, and weakest on the standard variable rate. If you’re modelling your own situation, find the current rate of a heat pump tariff in your region and re-run the cost-per-kWh-of-heat sum with that number in place of 26.32p.

The bit nobody counts: the gas standing charge

If a heat pump lets you disconnect the gas supply entirely - no gas hob, no gas fire, no gas water heating - you stop paying the gas standing charge. At 29.68p a day that is £108 a year before you have burned a single unit of anything, and it is a saving most comparisons quietly leave out.

The catch is that it only counts if the supply actually goes. Keep the gas hob and you keep the standing charge, and the saving is zero. Our calculator has a toggle for exactly this, because it swings the annual figure more than most people expect.

The upfront cost, and the grant

Running cost is only half the decision. A heat pump costs far more to install than a replacement gas boiler - and this is where the honest accounting has to include the grant.

In England and Wales, the Boiler Upgrade Scheme (BUS) pays £7,500 toward an air source or ground source heat pump replacing a fossil-fuel system. Your MCS-certified installer applies on your behalf and deducts it directly from the quote, so you pay the net figure. The scheme is funded through to 2028, any EPC rating now qualifies (since the March 2024 rule change), and there’s no separate homeowner application. (Source: Energy Saving Trust; Ofgem Boiler Upgrade Scheme.)

A few things the grant pages don’t always make obvious:

• Scotland and Northern Ireland are not covered by BUS. Scotland has its own route via Home Energy Scotland; NI has separate arrangements. If you’re outside England and Wales, the £7,500 figure simply doesn’t apply to you.
• From 21 July 2026 to 31 March 2027, an uplifted £9,000 grant is available - but only for off-gas-grid homes currently heated by oil or LPG. Homes on mains gas stay at £7,500. (Source: Grant UK; Energy Saving Trust.)
• The grant doesn’t make a heat pump free. Typical installed costs for a three-bed home land well above £7,500, so even after the grant you’re usually paying a meaningful net sum - often comparable to a premium gas boiler swap, sometimes more.

The fair way to frame the upfront question: the grant brings the net cost of a heat pump roughly into the territory of a high-end gas boiler replacement for many homes, but rarely below it. You’re not saving money on day one. The case rests on running costs and longevity over the years that follow.

Where gas still wins

An honest comparison has to include the cases the sales pages skip. A gas boiler may be the better call right now if:

• Your home is poorly insulated and you can’t fix that first. A heat pump in a draughty, single-glazed, uninsulated house will run hot flow temperatures, post a low SCOP, and cost more than gas to run. Insulation isn’t an optional upgrade alongside a heat pump - for many homes it’s a prerequisite for the heat pump to make sense at all.
• You only have small radiators and can’t or won’t resize them. Heat pumps want larger emitter surfaces to deliver heat at low flow temperatures. If you’re unwilling to change radiators, the heat pump is forced to run hot and inefficient.
• You’re outside England and Wales and don’t qualify for an equivalent grant, making the upfront gap much harder to justify.
• You’re staying in the property only a short time. The heat pump’s advantage accrues over years of running-cost savings. If you’ll have moved on within a few years, you may never recoup the higher upfront cost.
• Your existing boiler is fairly new and working fine. Replacing a functioning efficient boiler purely to switch fuel rarely pays back quickly. The strongest moment to switch is when the boiler is due for replacement anyway, so you’re comparing the heat pump’s net cost against a new boiler rather than against nothing.

None of these is a permanent verdict against heat pumps - insulate the house, resize the radiators, wait for the boiler to fail, and the maths flips. But pretending these cases don’t exist is exactly the kind of nudging this site exists to avoid.

So, which is cheaper?

Pulling it together honestly:

• Per unit of heat, on standard rates: a well-installed heat pump (SCOP 3.5+) costs about 7.5p per kWh of heat against 8.9p for a 90%-efficient gas boiler. Below a SCOP of about 3.0, gas is cheaper.
• With a heat pump tariff: the heat pump pulls clearly ahead on running cost.
• If the gas supply goes entirely: add roughly £108 a year in avoided standing charge.
• Upfront: the heat pump costs more even after the £7,500 grant, so the case is about running cost and longevity over time, not day-one savings.
• The deciding factor isn’t the technology - it’s your home and your installer. Insulation, radiator sizing, flow temperature, and tariff choice swing the answer further than the choice of fuel itself.

If you take one thing away: don’t trust a heat-pump-vs-gas number that doesn’t tell you the assumed SCOP, the assumed tariff, and whether the grant is included. Those three assumptions decide the entire result, and any source that hides them is hiding the answer.

Common questions

Is a heat pump cheaper to run than a gas boiler in the UK?

At the Ofgem price cap rates for 1 October 2026 to 31 December 2026, a heat pump achieving a SCOP of 3.5 costs about 7.5p per kWh of heat, against about 8.9p for a 90% efficient gas boiler — roughly 15% cheaper. The answer depends almost entirely on the quality of the installation: below a SCOP of about 3.0, gas is cheaper.

What SCOP does a heat pump need to beat gas?

At current cap rates, the break-even point against a 90% efficient gas boiler is a SCOP of about 2.97. Above that the heat pump is cheaper per unit of heat; below it the boiler is. A well-designed install in a decently insulated home should reach 3.5 to 4.5.

Why is electricity so much more expensive than gas per kWh?

Electricity currently costs about 3.3 times as much as gas per kWh under the price cap, because of how generation costs, network charges and policy levies fall on electricity bills. That ratio is the hurdle a heat pump's efficiency has to clear — it only wins if it is more than 3.3 times as efficient as your boiler at turning bought energy into heat.

How much is the heat pump grant in 2026?

The Boiler Upgrade Scheme pays £7,500 towards an air source or ground source heat pump replacing a fossil-fuel system in England and Wales. From 21 July 2026 to 31 March 2027 an uplifted £9,000 is available, but only for off-gas-grid homes currently heated by oil or LPG. Scotland and Northern Ireland are not covered and have separate schemes.

Run your own numbers

The figures above are national averages and worked examples. Your home isn’t average. Our heat pump calculator takes your actual usage, region, and system details and runs this same arithmetic with your numbers - showing every assumption and source as it goes. If you want to check whether a heat pump genuinely costs less for your home rather than the typical one, that’s the place to do it.

Every figure on this page is dated and sourced to Ofgem, the Energy Saving Trust, and published MCS/manufacturer performance data, verified on 14 September 2026. The energy rates are read from the current price cap period rather than typed into the text, so they update when Ofgem updates. Grant terms can change independently; check the current BUS terms before budgeting. Spotted something out of date or wrong? Email hello@energycosting.co.uk - we treat accuracy as the entire point.

Note on VAT: domestic electricity in Great Britain is temporarily zero-rated from 1 October 2026 to 31 March 2027. Gas stays at 5% throughout, and Northern Ireland is excluded. See also: heat pump calculator, heat pump methodology, solar & battery calculator.