"Heat pump" has become one of the most confusing phrases in home energy — not least because there are two very different kinds, and the government grant only applies to one of them. This guide explains the air-to-air heat pump: the type we install every week across Swindon, Salisbury, Chippenham and Devizes, which most people know by another name entirely — air conditioning.
An air-to-air heat pump doesn't generate heat the way a boiler or an electric fire does — it moves heat from one place to another, using the same refrigeration cycle as your fridge, run in reverse. Even cold winter air contains heat energy. The outdoor unit absorbs that energy into a refrigerant, a compressor concentrates it, and the indoor unit releases it into your room as warm air. In summer the cycle flips and the same machine pumps heat out of the room instead — which is why every system we fit both heats and cools.
Because it moves heat rather than making it, a heat pump delivers more heat energy than the electricity it consumes. The ratio is called the COP (coefficient of performance): a COP of 3.5 means 1kW of electricity in, 3.5kW of heat out. SCOP is the same idea averaged across a whole heating season, so it's the more honest number to compare units on. Modern units from Daikin, Mitsubishi Electric and the other leading brands typically achieve a SCOP of 4 or better — roughly 3–4kW of heat for every 1kW of electricity. A plug-in electric heater, by comparison, gives you exactly 1kW of heat per 1kW of electricity, every time.
The other kind of heat pump — air-to-water — heats water rather than air, feeding radiators, underfloor heating and a hot water cylinder. It's a boiler replacement, and it's a much bigger project. Here's how they compare:
| Air-to-air | Air-to-water | |
|---|---|---|
| What it heats | The air in your rooms, directly | Water for radiators / underfloor |
| Hot water (taps, showers)? | No | Yes, via a cylinder |
| Works with radiators? | No — has its own indoor units | Yes (often upsized) |
| Cools in summer? | Yes — it's air conditioning too | Generally no |
| Boiler Upgrade Scheme (£7,500 grant)? | Not eligible | Eligible |
| Typical installed cost (2026) | £1,600–£5,500 depending on rooms | £8,000–£15,000+ before grant |
| Disruption | 1–2 days, no wet system changes | Days to weeks, plumbing throughout |
So while air-to-air misses out on the £7,500 Boiler Upgrade Scheme grant, it costs a fraction of an air-to-water system to install in the first place — and it's the only one that gives you cooling in a heatwave as part of the deal.
Yes. It's the most common doubt we hear, and the most outdated. Modern units keep producing useful heat down to around -15°C — far colder than anything a Wiltshire winter throws at us. Efficiency does dip as the temperature falls (there's less heat in the air to harvest), but even on a frosty January morning in Devizes you're getting substantially more heat per kilowatt than any electric heater can offer.
A worked example. Say you're heating a living room with a 3.5kW unit, and electricity costs around 27p per kWh:
More detailed examples, including summer cooling costs, are in our running costs guide.
And that last point is worth repeating: every air-to-air system is also full air conditioning. One install, one outdoor unit, comfortable all year.
If you're weighing up a heat pump for a garden room, an extension or the whole house, tell us your town and the rooms involved and send us a message. We'll reply the same working day and arrange a free survey with a fixed supplied-and-fitted price, anywhere in Wiltshire.
Effectively, yes. A modern split air conditioning system is an air-to-air heat pump — the same machine runs in both directions, cooling the room in summer and heating it in winter. When you buy air conditioning from a proper installer today, a heat pump is what you're getting.
For room heating, yes in some homes — well-insulated properties, flats, bungalows and all-electric homes can be heated entirely by air-to-air units. But an air-to-air system doesn't heat water, so you'd still need an immersion heater, cylinder or other arrangement for hot water. Many households run it alongside the boiler instead, heating the most-used rooms cheaply and letting the boiler do less.
A typical 3.5kW unit heating a living room draws roughly 1kW of electricity on average. At around 27p per kWh in 2026, that's roughly 25–30p per hour for about 3.5kW of heat — where a 2kW electric panel heater costs around 54p per hour for far less warmth. Real usage varies with insulation, outside temperature and thermostat setting.
Tell us your town and the rooms you'd like heated or cooled — someone from our local team will come back to you as soon as possible with a fixed quote.
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