The advantages
High efficiency. The Energy Saving Trust says that for every unit of electricity used, a heat pump can return three to four times as much heat (300 to 400%). A new boiler converts roughly 85 to 90% of its fuel (85% is the Energy Saving Trust figure for a new boiler; A-rated models start at 90%). In the Energy Systems Catapult field trial, though, the median seasonal figure across 428 air source heat pumps was 2.93 (SPFH2), so build your expectations on field figures, not showroom ones; the efficiency guide explains why.
A large grant. In England and Wales the Boiler Upgrade Scheme gives £7,500 towards an air source or ground source heat pump, and £9,000 where the home has no mains gas and the replaced heating is oil or LPG (applications from 21 July 2026 to 31 March 2027). Your installer applies and the grant is deducted from the quote. See every grant band.
Cheaper to run than direct electric and, on the right tariff, competitive with gas. The Energy Saving Trust says replacing electric heating with a heat pump should cut electricity costs considerably, and that a heat pump time-of-use tariff can bring running costs below a gas boiler’s.
Low-carbon heat, long life. There is no combustion on site, and the Trust says the heat pump itself is likely to last 20 years or more, longer than the average gas or oil boiler. The lifespan guide covers what to expect.
Broad suitability. The Catapult trial installed 742 heat pumps and reported no significant difference in ashp spf by house type or age. After one heating season, 85% of surveyed participants said they were likely to recommend one.
The disadvantages
Upfront cost. The 2026 Q3 official median for an installed air source heat pump was £12,826 including the grant value, and £34,630 for ground source (DESNZ, 29 October 2026). After a £7,500 grant that is roughly £5,326 for air source. The Energy Saving Trust says a ground source heat pump with a borehole can reach around £57,000. See the installation cost guide and finance options.
Electricity is expensive per unit. At the Ofgem cap for 1 October to 31 December 2026, electricity is 26.32p/kWh against 7.97p/kWh for gas. On the illustrative model used across this site (12,000 kWh of heat, seasonal efficiency of 3.0), a heat pump costs about £1,053 a year against about £1,063 for gas, before standing charges. The gap closes with better design and a suitable tariff.
The house may need work. Heat pumps run at lower water temperatures; the Energy Saving Trust notes radiators often run at 35 to 45°C, so some radiators may need to be bigger, and a hot water cylinder is usually needed. That is added cost and disruption; the sizing guide and cylinder guide cover it.
Space and noise. You need a spot for an outdoor unit and a cupboard for a cylinder. In the Catapult trial the unit could not meet permitted-development noise criteria at about 5% of properties. Siting is a survey question; see the noise guide.
Performance depends on design and use. In the same trial 91.9% of properties had an in-situ seasonal figure below the designed one, with a median gap of 17.9%. The Trust says running a heat pump like a gas boiler leads to poor performance, so learning the controls matters.
Side by side
| Factor | In favour | Against |
|---|---|---|
| Upfront price | £7,500 grant (or £9,000 off-gas) is deducted | Median £12,826 before the grant |
| Running cost | Efficient; cheaper than direct electric | Electricity about 3.3 times the price of gas per unit at the 1 October to 31 December 2026 cap (the Energy Saving Trust says around four) |
| Comfort | Steady, low-temperature heat | Radiators may need upsizing; slower response |
| Hot water | Stored water at lower temperatures | Needs a cylinder and a periodic hot cycle above 60°C |
| Space | Small footprint outdoors | Outdoor unit plus cylinder cupboard |
| Lifespan | 20 years or more (Energy Saving Trust) | Annual service of around £150 |
What decides which side wins
Three things matter most. What you are replacing: a heat pump is a larger running-cost win over oil, LPG or direct electric than over a new gas boiler, which is why the £9,000 off-gas band exists. The design: a room-by-room heat-loss calculation and a sensible flow temperature set efficiency. Your tariff: the Trust says time-of-use tariffs can reduce running costs significantly, and the tariff guide explains how to compare them.
Try the figures with your own prices. The calculator below defaults to the Ofgem cap and a labelled illustrative house; change any number to match your bills.
Heat pump running cost against your current fuel
No details needed. Change any figure to match your own quote or bills. Results are indicative — an MCS installer’s heat-loss survey and written quote are what count.
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Difference per year at these prices.
Prices: Ofgem cap 1 October to 31 December 2026 — electricity 26.32p/kWh, gas 7.97p/kWh, gas standing charge 29.68p/day (GB average, Direct Debit); heating oil 114.8p/litre including 5% VAT (109.3p before VAT; BoilerJuice UK average for 1,000 litres, read 28 September 2026); 10.35 kWh per litre assumed. No VAT on household electricity from 1 October 2026 to 31 March 2027, which flatters heat pumps in this window. LPG prices vary too much to default — use your own bills. Illustrative, not a quote.
Before you decide
A balanced decision needs your own house in the numbers. Check the grant band with the eligibility checker, get two or three written quotes showing the heat-loss calculation, and ask for a predicted seasonal efficiency with its working. If the quotes come back with large radiator or cylinder lines, that is the design doing its job, not a sales trick, but compare them line by line using the quotes checklist.