Is a Heat Pump Cheaper Than Gas?

Why this comparison is so often argued badly

Electricity costs more per kilowatt hour than gas. That single fact is where most “heat pumps are expensive to run” posts start — and stop. They skip the other half of the story: a heat pump delivers more heat than the electricity it consumes.

A modern gas boiler might turn one unit of gas into roughly 0.9–0.94 units of heat. A well-designed heat pump might turn one unit of electricity into roughly 3–4 units of heat over a year (that seasonal figure is the SCOP). The higher electricity price is offset by using fewer units of fuel for the same heat.

Whether that offset is enough depends on the house and the installation. National averages and installer marketing both smooth over that. This page stays with the levers you can actually influence in a Devon or Cornwall home.

Side-by-side running costs (typical 3-bed)

These bands come from the same planning figures we use on our main heat pump running costs guide. They assume heating and hot water for a typical three-bed house and current domestic energy prices as used in that work.

Planning bands, not guarantees. Standing charges, exact tariffs and hot-water habits still move real bills.

Read the middle two heat pump rows carefully. The technology is the same family; the design quality is not. Most of the internet argument is people comparing a good gas boiler to a poorly set-up heat pump — or an optimised heat pump to an ancient oil boiler — and then declaring a universal winner.

How the maths actually works

At its simplest:

Annual heat demand (kWh) ÷ SCOP × electricity unit rate = annual running cost

Three inputs drive almost everything:

• 1.Heat demand — how much heat the building needs over a year. Size, insulation, airtightness and occupancy dominate.
• 2.SCOP — seasonal efficiency: heat delivered per unit of electricity across a full year, not a single lab test point.
• 3.Unit rate — what you pay per kWh of electricity (and, for the gas side of the comparison, per kWh of gas).

Example using figures from our running-cost work: a three-bed needing about 11,000 kWh of heat a year, electricity at 26p/kWh:

Around 0.7 SCOP points is easily £150–£250 a year on a typical house. That is why flow temperature, emitters and weather compensation matter more than brochure peak COP.

Flow temperature is where gas habits hurt heat pumps

Gas boilers are often run at high flow temperatures. Radiators get hot to the touch; rooms recover quickly. Heat pumps are at their best in the mid-30s to low-40s °C for much of the season. Force them higher for long periods because the radiators are too small, and SCOP falls — which is exactly when the vs-gas comparison starts to look ugly.

That is not a reason to reject heat pumps. It is a reason to take emitter sizing (or underfloor heating) seriously, and to use weather compensation properly rather than a fixed high flow “to be safe.”

More detail: flow temperature and efficiency · radiator upgrades.

Insulation changes both sides — but it matters more for heat pumps

Lower heat loss cuts gas bills and heat-pump bills. On a heat pump it also protects efficiency, because a lower-loss house can run at lower flow temperatures more of the year.

Solid-wall and older stock is common across Devon and Cornwall. A heat pump will not magic away a naked loft. Fabric work (even partial) is often the difference between “similar to gas” and “why is this so expensive.”

Tariffs: the quiet lever after install

Gas tariffs and electricity tariffs do not move in lockstep. Once the heat pump is in, moving from a standard single-rate electricity product to a well-matched heat pump or time-of-use tariff commonly saves in the region of £150–£300 a year in the figures we publish — depending on use and flexibility.

That will not rescue a badly designed system. It will improve a decent one. Standing charges still apply on both fuels; compare whole bills where you can, not unit rates in isolation.

Rural oil (and LPG) vs heat pump — the comparison that matters in the South West

A lot of Devon and Cornwall homes are not on mains gas. For those households the useful question is not “heat pump versus a new combi.” It is heat pump versus oil or LPG fills — higher fuel cost, price spikes, tank space, and a different grant position.

Indicative annual running costs

Using the same planning bands as the rest of this page and our main running-costs guide:

Oil and LPG bills move with wholesale prices and how you buy. Use your last 12–24 months of fills as the baseline — not a national average from a brochure.

Why oil switchers often see a clearer running-cost case

• 1.Fuel cost per unit of heat — oil and LPG are usually more expensive delivered heat than mains gas, so the heat pump’s efficiency advantage has more room to show.
• 2.Volatility — tank fills jump; electricity is not immune to price changes, but the “surprise invoice after a cold month of oil” pattern is familiar in rural areas.
• 3.Standing practicalities — tank inspections, sludge, space, and delivery access all sit outside the pure kWh comparison.

None of that means a heat pump is automatic. A leaky farmhouse with tiny radiators can still produce a disappointing electricity bill. It does mean the starting point is often worse on oil than on modern gas — so a competent design has more headroom to improve day-to-day costs.

Grant position for oil and LPG (rural / off-gas)

Running cost is only half the decision. Upfront support currently differs:

The higher rate is aimed at off-gas homes — which describes a large slice of rural Devon and Cornwall. The legal test is fuel type + no mains gas, not a “rural” postcode label. Applications for the uplift run in a defined window (from 21 July 2026, currently expected through to 31 March 2027 — always check live GOV.UK wording).

On the same install cost, £9,000 instead of £7,500 is £1,500 more off the quote. That sits on top of any running-cost improvement versus oil fills.

A simple way to stress-test your own numbers

1. Add up oil or LPG spend for the last full year (or two) including delivery.
2. Note whether that winter was mild or hard — one year is noisy.
3. Compare to a heat pump planning band for your size of home (£850–£1,400 is the typical 3-bed heat pump range we publish; good design trends lower).
4. Subtract the grant difference if you are oil/LPG off-gas (£9,000 vs £7,500 where eligible).
5. Only then layer in emitters, insulation and tariff — those decide whether you land in the “good” or “average” heat pump row.

If your oil history is already under £1,200 a year in a tight, well-insulated house, the running-cost gap versus a heat pump may be modest and the decision becomes more about comfort, maintenance and carbon. If you are routinely in the £1,600–£2,500 band, the running-cost case is usually much easier to see — provided the heat pump is designed properly.

More on grants: Government grants & schemes in Devon & Cornwall. Planning band for your home: heat pump estimator (oil path uses the £9,000 BUS rate in the net cost band).

When gas can still look cheaper to run

Be honest about the failure modes. A heat pump can cost more to run than a modern gas boiler when:

• •Emitters are left too small — high flow temperatures for long periods, SCOP collapses.
• •Heat loss was understated — the unit works harder than the quote assumed.
• •Controls copy old boiler habits — deep setbacks and hard recovery, short cycling.
• •Tariff is ignored — standard rate forever while gas stays relatively cheap per kWh.
• •The system is badly oversized or undersized — both hurt seasonal performance.

Those are mostly design, fabric and commissioning issues. They are common enough that scepticism is understandable — and fixable more often than “heat pumps don’t work” suggests.

Costs are not flat through the year

Like gas, heat pump use clusters in winter. From our running-cost guide, a typical 3-bed pattern looks roughly like this:

Summer is mostly hot water. Comparing a January heat-pump bill to a mild-spring gas bill is how social media arguments go wrong.

Not every home is a “typical 3-bed”

Heat pump annual bands from the same dataset:

Gas scales with heat demand too. The vs-gas question is the same shape; the absolute pounds change with the building.

Honest bottom line

Frequently asked questions