Ask ten installers what a heat pump costs to run and you will get ten answers, most of them useless. Some quote a best case they have never measured. Some quote a national average that has nothing to do with your house.

The honest answer is that running cost comes down to two numbers: what you pay per unit of electricity, and how many units of heat your system produces for each unit of electricity it uses.

The first is set by your tariff. The second is set by whoever designed your system.

Here are the real figures as they stand today.

Where energy prices sit right now

The Ofgem price cap for 1 July to 30 September 2026, national average, direct debit, including VAT:

Electricity Unit rate - 26.11p per kWh. Standing charge - 57.19p per day

Gas Unit rate - 7.33p per kWh. Standing charge - 29.04p per day

We are in the Southern region, so the local numbers are slightly different: electricity 26.42p per kWh with a 49.70p daily standing charge, gas 7.53p per kWh with a 28.53p standing charge.

That puts electricity at roughly 3.5 times the price of gas. That ratio, the spark gap, is the single number that decides whether a heat pump saves you money on a standard tariff.

One thing worth noting: gas went up about 24% in July while electricity rose about 5%. The gap narrowed slightly, which helps the heat pump case. This narrowing is likely to continue into the future, as the Net Zero deadline gets ever nearer.

The number your system has to beat

A modern condensing gas boiler running well delivers about 90% of the gas it burns as useful heat. So each kWh of heat actually costs you 7.53 divided by 0.9, which is 8.37p in our region.

For a heat pump to match that on the standard cap rate, it needs to produce heat at 8.37p per kWh too. At 26.42p per unit of electricity, that means a seasonal efficiency, the SCOP, of about 3.2.

So: a heat pump on a standard tariff needs a real, measured SCOP above about 3.2 to beat a good gas boiler on unit cost alone.

That is the honest threshold. Anyone who tells you a heat pump always saves money regardless of design is selling, not engineering.

What this looks like in a real house

Take a house using 12,000 kWh of heat a year, space heating plus hot water. That is a fairly typical detached or large semi in this area after some basic insulation work.

Gas boiler at 90% efficiency: 13,333 kWh of gas at 7.53p, which is £1,004, plus the gas standing charge of £104. Call it £1,108 a year.

Heat pump, on the standard cap rate:

At a SCOP of 4.0: 3,000 kWh of electricity a year, £793. That is £315 cheaper than the boiler.

At a SCOP of 3.5: 3,429 kWh, £906. £202 cheaper.

At a SCOP of 3.2: 3,750 kWh, £991. £117 cheaper, and that is the break even point on unit cost alone.

At a SCOP of 2.5: 4,800 kWh, £1,268. £160 more expensive than the boiler it replaced.

Look at the bottom row. A poorly designed heat pump running at a SCOP of 2.5 costs more than the boiler it replaced. This is exactly what has happened in a lot of homes, and it is why heat pumps have a mixed reputation.

The difference between the top row and the bottom row is not the brand on the box. It is flow temperature, emitter sizing, controls and commissioning.

The standing charge nobody mentions

If you take the gas out entirely, you stop paying the gas standing charge. In our region that is 28.53p a day, or £104 a year, before you have used a single unit.

On the 12,000 kWh house below, that £104 is worth about 0.3 on the breakeven. In other words, once you account for losing the gas connection entirely, the real breakeven on total annual cost is a SCOP of around 2.9, not 3.2.

Small point, but installers routinely leave it out of comparisons and it is real money.

Heat pump tariffs change the picture

The figures above are on the flat cap rate. Most heat pump owners should not be on a flat rate.

Octopus Cosy is the most established heat pump tariff and it publishes its rates openly.

For our region today:

Off-peak 13.11p per kWh, covering 04:00 to 07:00, 13:00 to 16:00 and 22:00 to midnight

Day rate 26.72p per kWh

Peak 40.08p per kWh, 16:00 to 19:00

Standing charge 47.71p a day

Eight hours a day at roughly half price. A well set up heat pump with a decently insulated house and a sensible cylinder can shift a large share of its load into those windows, particularly the hot water reheat and a pre-heat before the evening peak.

If you genuinely get 50% of your heat pump load into the cheap hours, your blended rate is about 19.9p. On our 12,000 kWh house at a SCOP of 4.0, that is about £598 a year, roughly £510 less than the gas boiler.

Two honest caveats. First, the tariff applies to your whole house, not just the heat pump, so that 40.08p peak window hits your oven and your kettle too. Second, load shifting only works if the system was designed with enough thermal mass and the controls to do it. Bolting a smart tariff onto a badly designed system does not fix the system.

Other suppliers now offer heat pump tariffs, including EDF, British Gas, ScottishPower and E.ON Next. Most of them do not publish full rate tables, so you have to get a quote and do the arithmetic yourself. OVO's Heat Pump Plus tariff, which was popular, closed to new customers in February 2026.

What changes on 1 October 2026

VAT on domestic electricity drops from 5% to zero on 1 October 2026. Gas stays at 5%.

That is about a 4.8% cut to your electricity unit rate, and it is the first measure that genuinely tilts the price ratio towards electricity rather than just moving money around. On today's rates it would take our regional electricity price to roughly 25.2p and pull the unit cost breakeven SCOP down to about 3.0.

Two things to be careful about. The October price cap has not been announced yet, so the net effect is not yet known. And the sources disagree on whether the VAT cut is permanent or runs initially to March 2027 with a review at the Autumn Budget. Do not bank on it being permanent.

Where the grant stands

The Boiler Upgrade Scheme is in better shape than it has been:

£7,500 for an air source or ground source heat pump

£9,000 if your property is off the gas grid and you are replacing oil or LPG. This uplift runs from 21 July 2026 to 31 March 2027

The EPC requirement was removed on 28 April 2026. You no longer need a valid EPC to apply. Alternative evidence is accepted, such as a recent utility bill or fuel receipt and photos of the existing system

The scheme is funded through to 2030, so the cliff edge people were worried about has moved

The grant is deducted from your quote by us, not claimed back by you. There is no paperwork for you to chase.

If you are on oil in one of the villages around Guildford, Albury, Shere, Wonersh, that £9,000 window closing in March 2027 is worth paying attention to. Oil replacement is where the running cost case is strongest anyway, because you are comparing against a fuel that costs more per kWh than mains gas and a boiler that is usually less efficient than a modern condensing unit.

Why the design decides the running cost

Everything above assumes the SCOP figure is real. Here is the uncomfortable part of the industry: a lot of them are not.

Analysis of homeowner forum data published in June 2026 found complaints about heat pump installations rose roughly twenty-four fold between 2021 and 2024. The most common faults were oversized units short cycling, and flow temperatures left at 55 to 60 degrees when they should have been 35 to 45. That second one alone carries a running cost penalty of around 40%.

A Which? report in July 2026 found 88% of people had difficulty during the quoting process and 29% described getting a heat pump as "a gamble."

It should not be a gamble. It is arithmetic. Lower the flow temperature and the efficiency rises, roughly 2.5% for every degree. Size the emitters for the worst room in the house, run weather compensation properly, keep the hydraulics simple, and a SCOP of 4 or better is achievable in most Surrey housing stock.

Get any of that wrong and you land at 2.5 and wonder why your bills went up.

That is not a marketing claim, it is what the physics does. The question to ask any installer is not "what will it cost to run," it is "what design flow temperature have you designed to, and what did you do to get it there."

What to do next

If you want a straight answer for your own house rather than a table of averages, that starts with a proper room by room heat loss survey. Not a desktop estimate, not a number pulled off your EPC.

We cover Guildford, Woking, Dorking, Farnham and the surrounding villages. Book a heat loss survey and we will show you the design flow temperature we can achieve in your house, what it will do to your emitters, and what the running cost actually works out at on your tariff.

Prices quoted are the Ofgem cap for 1 July to 30 September 2026 and Cosy Octopus rates as published on 9 August 2026. Energy prices change quarterly. We update this article each time the cap moves.

Sources

Ofgem energy price cap unit rates and standing charges

Boiler Upgrade Scheme: what you can get, GOV.UK

Notice of approved grant categories and values for the Boiler Upgrade Scheme

Cosy Octopus

VAT cut on household electricity, GOV.UK, 21 July 2026

24 times more complaints in three years, Installer Online

Which?, Beyond Affordability: Why Heat Pumps Feel Like a Gamble