Scotland Regional Winner, Heating Installer Awards 2026Highly Commended, Scottish Energy Efficiency Awards 2025
🎉 Scotland Regional Winner at the Heating Installer Awards 2026
Scotland Regional Winner, Heating Installer Awards 2026Highly Commended, Scottish Energy Efficiency Awards 2025
🎉 Scotland Regional Winner at the Heating Installer Awards 2026
Home / Blog / Heat pump vs air conditioner
An air conditioner with a heating setting is a heat pump. For a Scottish home, the heat pump vs air conditioner question turns on where each machine puts its heat. An air to air unit blows warm air into the room its indoor head hangs in. An air to water heat pump, the type Home Energy Scotland funds and Scottish heating installers mean by “air source heat pump”, heats water for your radiators, underfloor pipes and hot water cylinder.
Sean Hogan · Heat Geek engineer · Updated October 2026 · 13 min read
That split decides which system can replace a boiler, which one Home Energy Scotland will fund and which one keeps every room warm through a Scottish January. We design and install air to water air source heat pumps for radiators, underfloor heating and hot water; air conditioning is not a service we offer.
Both machines move heat with the same refrigerant loop. A fan pulls outdoor air across a coil of refrigerant colder than that air, the refrigerant absorbs the heat and boils, and a compressor squeezes the vapour until it runs hotter than your home. Our explainer on how an air source heat pump works follows that cycle step by step, defrosting included.
A split air conditioner with a heating mode runs the cycle in either direction. In summer a reversing valve sends the heat outside and the indoor head blows cool air; in winter the valve flips, the outdoor unit gathers heat and the indoor head blows it into the room as warm air. Heating engineers call this an air to air heat pump, and online listings sell the same box as a heat pump air conditioner.
An air to water heat pump hands its heat to water. A heat exchanger passes it from the refrigerant into the water, and that water travels round a wet heating circuit like the one a gas or oil boiler feeds now. Home Energy Scotland funds this type, and Scottish heating installers mean it when they quote an “air source heat pump”, so check which one a quote describes before you compare prices.
An air to air system heats the air in the rooms that have an indoor head. Each head is a fan coil on the wall, ceiling or floor, and a set-up might give the living room and one or two bedrooms a head each. Heat reaches the hall, bathroom and box room only if doors stay open, so those rooms often end up on plug-in or panel heaters.
Warm air also rises. In a Victorian tenement or a sandstone villa with high ceilings and cornicing, a wall-mounted head sends its warm air up toward the ceiling before it reaches the sofa.
An air to water heat pump feeds one circuit that reaches every radiator and every underfloor loop in the house, the bathroom towel rail included. Weather compensation sets the water temperature from the reading outside, so the radiators run warm for long hours rather than hot for short bursts. Many existing radiators can stay; a few in the coldest rooms tend to need a larger size to give enough heat at a low flow temperature, and a room-by-room heat loss calculation shows which ones.
Flats with electric storage heaters and no wet heating system are where air to air units look most tempting. There, an air to water heat pump means new pipework, radiators or underfloor heating, and a place for a cylinder, which is more work up front. The survey for a flat like that has to answer two practical questions: whether the building can take an outdoor unit, and where a cylinder could sit.
“We had an excellent experience with Sean and his team at Aventus Eco. They recently installed our air source heat pump and hot water system, and Sean was hands-on throughout the entire process.”
Tony McCole, ★★★★★ Google Review
An air to air heat pump heats no water. Install one and your showers, baths and kitchen taps stay on whatever heats them now: a gas combi, an oil boiler, an electric shower or an immersion heater in the cylinder. If the plan is to take the gas or oil away, the immersion heater becomes the default, and it turns one unit of electricity into one unit of heat.
Ofgem’s price cap for 1 October to 31 December 2026 puts electricity at an average of 26.32p per kWh by Direct Debit, with no VAT on electricity from 1 October 2026 to 31 March 2027. Immersion hot water therefore costs 26.32p for each kWh of heat in the tank.
A heat pump heating the same cylinder at an assumed 250%, a working figure for the hotter water a cylinder needs, brings that down to about 10.5p, and at 300% to about 8.8p.
An air to water system heats the cylinder from the same outdoor unit that heats the radiators, switching between the two jobs through a valve. The cylinder needs a space about the size of an airing cupboard, and in plenty of Scottish houses the old airing cupboard is where it goes.
Both systems run on electricity, so in any air source heat pump vs air conditioner cost comparison the price of a kilowatt-hour of heat comes down to the efficiency of the machine at that moment.
Divide the unit rate by the efficiency and you have the cost of the heat itself.
| Heat source (assumed efficiency) | Cost per kWh of heat |
|---|---|
| Immersion heater or panel heater (100%) | 26.3p |
| Heat pump running at 200% | 13.2p |
| Heat pump running at 300% | 8.8p |
| Heat pump running at 400% | 6.6p |
| Condensing gas boiler (90%), for reference | 8.9p |
Electricity at 26.32p and gas at 7.97p per kWh, Ofgem price cap 1 October to 31 December 2026 (Great Britain averages, Direct Debit). The efficiencies are illustrative assumptions chosen to show the spread between direct electric heat and a heat pump.
An air to air unit and an air to water heat pump can both sit in the 300% to 400% rows on a mild day. The gap between them on the bill comes from coverage. Once the boiler goes, an air to air system heating the living room and two bedrooms leaves the hot water on the 26.3p row, and the hall, bathroom and spare room on plug-in heaters in the same row. An air to water system takes the whole house, hot water included, off that row. The full-year picture, with time-of-use tariffs, is in our breakdown of heat pump running costs in Scotland.
Flow temperature moves the air to water figure. The lower the water temperature the radiators need, the higher the efficiency, which is why the design starts from heat loss and emitter sizes. A Bathgate new build we designed around a 35°C flow logged 440% on its controller across a monitored November month, with outdoor temperatures between 0 and minus 5°C. At October 2026 cap rates that works out at about 6p per kWh of heat. A new build loses less heat than a stone villa, so treat it as the result careful design reaches in a well-insulated house.
“Since the instal, the house now constantly feels like it is at a comfortable temperature, and the amount of energy we use on a daily basis compared to our old electric boiler has been reduced.”
Stuart Campbell, ★★★★★ Google Review
Home Energy Scotland funds heat pumps that provide 100% of a home’s heating and hot water, and its grants and loans page names the exceptions in one line: “Hybrid heat pumps, air-to-air heat pumps and exhaust air heat pumps are not eligible for funding.” We checked that wording on homeenergyscotland.org on 14 October 2026.
The hot water half of the rule excludes air to air on its own, since the unit heats no water. An air to water heat pump that carries the whole house can attract a grant of up to £7,500, rising to £9,000 in remote rural, island or off-gas accessible rural areas, plus an optional interest-free loan of up to £7,500. Home Energy Scotland also requires the installer and the product to be MCS certified. Our guide to heat pump grants in Scotland walks through eligibility and the application in order.
Sequencing can cost you as well. Home Energy Scotland funds a replacement heat pump with a loan only, with no grant. If you fit air to air units now and plan an air to water system in a few years, ask Home Energy Scotland in writing how it would treat that second system before you buy the first.
“Our household was going through the Home Energy Scotland grant and loan scheme as we qualified for a heat pump. Sean came recommended by an insulation company and I’m glad that I reached out.”
Dale Lafferty, ★★★★★ Google Review
The Met Office’s 1991 to 2020 averages for its Glasgow Springburn station give a mean daily maximum of 19.21°C in July and 18.60°C in August. The same station logs 44.58 days of air frost a year. A Scottish home spends its energy on heating, and the design figure that sizes a heat pump comes from the cold end of the year.
Hot spells still happen. A top-floor flat under a slate roof or a dormer bedroom facing south can get too warm to sleep in for a few days in July, and that is the case people have in mind when they search for air conditioning in Glasgow or Edinburgh. Across Glasgow’s tenements and sandstone villas, our heat pump installation work in Glasgow sizes each system for that winter load, with heating and hot water as the job.
Some air to water heat pumps are reversible and can send cool water round underfloor pipes on a hot day, with controls that keep the floor above the dew point so no condensation forms on it. Radiators give out little cooling. The systems we design and fit are set up for heating and hot water only, so if summer cooling matters to you, ask the manufacturer what a reversible model and your emitters could deliver before you buy.
Air conditioning puts a fan in the room. Each indoor head carries one, and you hear it most at night in a bedroom.
An air to water system keeps its fan outdoors: the indoor kit is a cylinder, a circulating pump and the controls, tucked into a cupboard.
Both systems have an outdoor unit, and its position against your neighbour’s windows is the noise question that planning rules care about.
In Scotland, a domestic air source heat pump that stays inside the limits of Class 6H counts as permitted development, under the 2016 amendment to the permitted development order published on legislation.gov.uk. The class allows one air source heat pump per building, no part sticking out more than 1 metre from a wall or roof, a rear ground-floor position only in a conservation area, and nothing within the curtilage of a listed building. The installation also has to meet the MCS Planning Standards, which include a noise calculation at the nearest neighbouring property.
One condition matters for air conditioning. Class 6H says the unit must be used only for the purpose of providing “domestic heating or hot water”. A unit fitted to cool your rooms sits outside that wording. The Scottish Government consulted from 3 September to 27 October 2025 on letting heat pumps installed under permitted development run for heating and cooling, though not for cooling alone, pointing to England’s equivalent change, which lets air-to-air heat pumps benefit. A summary of the responses followed in March 2026. Our search of legislation.gov.uk on 14 October 2026 found no permitted development amendment order from 2025 or 2026, and the revised Class 6H text there still carries the heating-or-hot-water condition, so check with your council before a unit goes up for cooling.
The one-unit limit has a knock-on effect too. An air conditioner’s outdoor unit is an air source heat pump in engineering terms, so ask the council’s planning department whether one already on the building counts toward the limit before a second unit goes up. Our guide to heat pump planning permission in Scotland covers conservation areas, listed buildings and tenements in detail.
The heat pump vs air conditioner choice comes down to how much heat your home loses on a cold Scottish day, what your radiators can deliver and where a cylinder and an outdoor unit can go. A £0 survey measures the heat loss room by room, checks the outdoor unit position against the planning and noise rules, and shows whether the design meets Home Energy Scotland’s 100% heating and hot water condition.
They share the same refrigerant cycle. An air conditioner with a heating mode is an air to air heat pump that warms the room it sits in. The air source heat pump fitted in Scottish homes in place of a boiler is the air to water type, which heats radiators, underfloor heating and the hot water cylinder.
An air to air unit cools rooms the way an air conditioner does. Some air to water heat pumps are reversible and can cool through underfloor pipes with dew point controls, while radiators give little cooling. In Scotland, permitted development covers a heat pump used for heating or hot water, so check with your council before fitting a unit for cooling.
No. Home Energy Scotland lists air-to-air heat pumps as not eligible for funding. An air to water heat pump that provides 100% of a home’s heating and hot water can attract up to £7,500, or £9,000 in eligible rural and island areas in Scotland, plus an optional interest-free loan of up to £7,500.
No. An air to air unit heats air only, so your hot water stays on a boiler, an electric shower or an immersion heater. At Ofgem’s October 2026 cap, immersion hot water costs 26.32p per kWh of heat, against about 10.5p from a heat pump at an assumed 250%.
Check with your council first. Scotland’s permitted development class for air source heat pumps requires the unit to be used only for domestic heating or hot water, so a unit fitted for cooling falls outside it. Listed buildings and conservation areas bring tighter rules on top.
Per kWh of heat the two can run at similar efficiencies, because both are heat pumps on the same electricity price. An air to air system heats only the rooms with an indoor head, so in a Scottish home the hot water and the other rooms stay on direct electric heat at 26.32p per kWh, which raises the total bill.
A £0 survey measures your heat loss room by room and checks where a cylinder and an outdoor unit can go.
Get my £0 survey 0141 673 1810
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