If you only learn one piece of jargon before getting a heat pump quote, make it the spark gap: the ratio between what you pay for a unit of electricity and a unit of gas. Heat pumps run on electricity, gas boilers on gas — so this one number decides who wins on running cost.
The rule of thumb is simple: if your heat pump’s efficiency (SCOP) is higher than the spark gap, the heat pump is cheaper to run than a gas boiler.
The current numbers
Figures track the Ofgem price cap for Northern Scotland, last refreshed July 2026.
| Price | |
|---|---|
| Electricity (standard tariff) | 26.11p/kWh |
| Mains gas | 7.33p/kWh |
| Spark gap (electricity ÷ gas) | ≈ 3.6 |
| Heat from a 90%-efficient gas boiler | 8.14p/kWh |
| Heat from a heat pump at SCOP 4.0, standard tariff | 6.53p/kWh |
| Heat from a heat pump at SCOP 4.0, heat-pump tariff (18p) | 4.5p/kWh |
Two things follow from that table.
A well-designed heat pump already beats mains gas. With the spark gap at roughly 3.6, a heat pump needs a SCOP above about 3.6 to undercut a gas boiler on a standard tariff. A well-designed system delivers a SCOP of 4.0+ — over 400% efficiency — and we design for high seasonal performance. The margin over gas is real, if modest.
Dedicated heat-pump tariffs change the picture entirely. Several suppliers now offer time-of-use tariffs designed around heat pumps, bringing the effective rate down to around 18p/kWh. At SCOP 4.0 that’s heat at roughly 4.5p/kWh — well under half the cost of gas heat, and a fraction of oil or LPG.
Why the gap keeps narrowing
Historically, UK electricity carried most of the policy levies while gas carried few — which kept electricity artificially expensive relative to gas. That balance is shifting, and every shift moves the running-cost case further in the heat pump’s favour. If you ran the numbers a couple of years ago and they didn’t stack up, they’re worth running again.
What this means if you’re on oil or LPG
The spark gap conversation is about mains gas, the hardest fuel to beat. Off the gas grid — as much of the Highlands is — the comparison isn’t close: delivered heat from oil currently costs around 10p/kWh and bulk LPG around 14.5p/kWh, against roughly 4.5–6.5p/kWh from a well-designed heat pump. That’s before the Home Energy Scotland grant takes up to £7,500 (up to £9,000 in rural areas) off the install.
Savings always depend on your building, your tariff and how the system is designed — which is why we start every job with a room-by-room heat-loss survey rather than a generic promise. Ask us for an honest assessment of your numbers.