Air conditioning vs heat pumps: can AC heat your home?

Air conditioning and heat pumps are not really rivals, because a reverse-cycle (heat and cool) air conditioner is already a heat pump. More precisely, it is an air-to-air heat pump: the same split-system technology, using a refrigerant to move heat, that cools your rooms in summer and heats them in winter. So yes, the right kind of home air conditioning can heat your house.

The genuine comparison is not "air con versus heat pump" at all. It is air-to-air versus air-to-water. An air-to-air heat pump (your reverse-cycle AC) heats and cools the air in your rooms. An air-to-water heat pump, the system most people picture when they hear "air source heat pump", heats the water in your radiators, underfloor heating and hot water cylinder. This guide explains the difference plainly, then compares the two on what they heat, cooling, cost, efficiency, hot water, grants and planning, so you can tell which one your home actually needs.

Is a reverse-cycle air conditioner the same as a heat pump?

Yes. A unit that both heats and cools is commonly sold as an air-to-air heat pump; a unit that only cools is sold as an air conditioner. The hardware and the refrigerant cycle inside are identical. The only difference is whether the system can run in reverse.

Here is the mechanism in plain terms. In cooling mode, the unit extracts heat from inside your room and dumps it outside, exactly like a fridge. A reverse-cycle unit can flip that cycle: in heating mode it extracts warmth from the outside air, even on a cold day, and releases it indoors. That reversing valve is the whole trick. It is why "reverse cycle" and "air-to-air heat pump" describe the same thing, and why a good split-system air conditioner is a genuine winter heater, not just a summer luxury.

One practical limit: an air-to-air heat pump can only heat or cool at any one time, not both at once. A multi-split system can still set different rooms to different temperatures, but only within the same mode across the system.

For a fuller walk-through of the refrigerant cycle, see our explainer on how air conditioning works.

Air-to-air vs air-to-water heat pumps

This is the comparison that actually matters. Both are air-source heat pumps, and both are far more efficient than a gas or oil boiler. What they heat, and how they fit your home, is where they part ways.

The single biggest distinction is hot water. Air-to-air systems heat and cool the air directly, but they usually do not provide domestic hot water for your taps and shower. If you go air-to-air, you still need a separate hot water solution, such as an immersion cylinder, point-of-use electric heaters, or a model specifically designed to also heat a cylinder. Air-to-water systems, by contrast, heat a hot water cylinder as standard.

The Energy Saving Trust rates air-to-air as a good fit for smaller homes and flats, with a smaller outdoor unit than an air-to-water system and the bonus of summer cooling. The trade-offs: the indoor units can be noisier than other heat pumps, you need new refrigerant pipework for each indoor unit, and because the system recirculates room air rather than supplying fresh air, you still need proper ventilation.

A reverse-cycle air conditioner is already a heat pump. The real question is whether you want to heat the air in a few rooms, or the water across the whole house.

When does each one make sense?

Choose an air-to-air heat pump (reverse-cycle AC) when you want efficient heating for one or a few rooms and you also want cooling in summer. It suits smaller homes, flats, extensions and finished homes where ripping out a working wet heating system makes no sense. It responds fast and the outdoor unit is compact.

Choose an air-to-water heat pump (air source) when you are replacing your boiler and want one low-carbon system to heat the whole house and your hot water through your existing radiators or underfloor heating. It is the most common domestic heat pump in the UK and suits most home types, but it does not cool.

Plenty of homes end up with both logics in play: an air-to-water system for whole-home heat and hot water, and air-to-air in a bedroom or home office for summer cooling.

How efficient are they, and will they cut my bills?

Heat pumps of either type are more than three times as efficient as a gas or oil boiler, according to the Energy Saving Trust. They deliver several units of heat for each unit of electricity. Heating efficiency is measured as SCOP (Seasonal Coefficient of Performance), and cooling efficiency as SEER (Seasonal Energy Efficiency Ratio); both are seasonal averages, and higher is better.

Efficiency on its own does not guarantee a cheaper bill, though, and this catches people out. Electricity costs roughly four times the unit price of gas in the UK. So even though a heat pump is three-times-plus more efficient, the running cost can land close to, or slightly above, a modern gas boiler. The gap narrows when the system is well designed and you are on the right tariff.

What do they cost to run?

Running cost comes down to the unit's electrical input and your electricity unit rate. The simple sum is:

Cost per hour = electrical input (kW) x unit rate (£/kWh)

Using the Ofgem price cap unit rate of 26.11p/kWh for July to September 2026:

• A unit drawing 1kW of electricity costs about 26p per hour to run (1 x £0.2611).

• A unit drawing 2.5kW costs about 65p per hour (2.5 x £0.2611).

The key point for heating is that the electrical input is only a fraction of the heat delivered. With a SCOP above 3, every 1kW of electricity you pay for produces more than 3kW of heat, which is what makes a reverse-cycle unit a sensible winter heater. As a rough industry guide, installers quote anywhere from around 24p to £1.23 per hour for a 1kW to 5kW unit, depending on how hard it is working.

Prices and rates correct as of July 2026. The energy price cap changes quarterly, so check the current Ofgem rate before budgeting.

For a deeper breakdown, see our guide to air conditioning running costs.

How much do they cost to buy and install?

Costs vary by home, number of rooms, pipe runs and access, so treat these as typical bands rather than fixed quotes.

The air-to-air figures are from the Energy Saving Trust, with installer cross-checks landing in a similar £2,000 to £4,000 range for a typical 5kW system. The £11,000 air-to-water figure is a typical estimate from the Energy Saving Trust for a whole-home system, so use it as a guide, not a quote. Always get quotes from at least three MCS-certified installers.

Is there a grant for air conditioning or air-to-air heat pumps?

This is where the picture is changing, so read it carefully.

On 18 November 2025 the Boiler Upgrade Scheme was expanded to add a £2,500 grant for air-to-air heat pumps (and £2,500 for heat batteries), alongside the existing £7,500 for air source (air-to-water) and ground source heat pumps. This is the first time air-conditioning-style units have been in line for UK government funding.

The air-to-air grant is now live. It took effect on 28 April 2026, and the GOV.UK "what you can get" page now lists £2,500 towards an air-to-air heat pump alongside £7,500 for air source and ground source and £5,000 for biomass. Check GOV.UK for the exact eligibility conditions before you rely on it.

A few conditions are clear from how the scheme works:

• It applies to England and Wales only. Scotland uses Home Energy Scotland grants and loans; Northern Ireland has no equivalent heat-pump grant at present.

• The grant is for replacing an existing fossil-fuel or electric heating system (gas, oil, LPG or electric, including storage heaters) with a qualifying low-carbon system, installed by an MCS-certified installer.

• You cannot claim it to replace an existing low-carbon system, nor for a hybrid such as a gas boiler plus heat pump.

By extension, the air-to-air grant is tied to the unit providing heating and replacing an existing fossil-fuel or electric heating system. It is not intended for comfort cooling that keeps a working gas boiler in place. The precise conditions are published on GOV.UK.

Grant details correct as of August 2026 and subject to change. Confirm current amounts and eligibility on GOV.UK before applying.

Do I need planning permission?

For a reverse-cycle unit on a house, often not, because a domestic air-source heat pump can fall under permitted development (Class G in England), subject to conditions. But there is a crucial catch that turns directly on the heat-versus-cool point.

One Class G condition is that the unit is not used solely for cooling. A reverse-cycle air conditioner that heats and cools can therefore qualify as permitted development. A cooling-only air conditioner does not meet that condition and generally needs full planning permission. This is the practical reason a heat-and-cool unit is easier to install than a cooling-only one.

Other Class G limits apply too: there are outdoor-unit size and siting rules, and tighter restrictions on flats, listed buildings, conservation areas and scheduled monuments. Scotland, Wales and Northern Ireland have their own rules. Always check with your local planning authority before you commit.

You will also need an MCS-certified installer to qualify for any grant, and any work on the refrigerant must be done by an F-Gas certified engineer. A refrigerant split system is not a DIY job.

For more on the options, see the types of home air conditioning hub, or read whether air conditioning is worth it for your home.