Most UK businesses treat air conditioning as a summer expense and a gas boiler as a winter one. If your building has modern air conditioning installed, that assumption is costing you money — because almost every system fitted in the last twenty years is a heat pump, and it can heat your building as well as cool it.
With winter energy budgets being set now, this is the right month to ask a straightforward commercial question: is it cheaper to heat your premises with the air conditioning you already own, or with the boiler you already pay to maintain? Here is the honest answer, with the numbers.
Your air conditioning is already a heat pump
An air conditioning system moves heat rather than creating it. In summer it takes heat out of the building and rejects it outside. Run the cycle in reverse and it takes heat from outside air — even at low temperatures — and delivers it indoors.
That reversal is not an upgrade or an add-on. If you have a split system, a multi-split, or a VRV/VRF system from Daikin or Mitsubishi installed within roughly the last two decades, heating mode is almost certainly already there. In our experience taking on new maintenance clients, a significant number are running gas heating through the winter while a perfectly capable heat pump sits idle on the roof.
Why heat pumps beat direct electric heating
A fan heater or electric panel heater converts one unit of electricity into one unit of heat. A heat pump typically delivers three to four units of heat for every unit of electricity it consumes, because most of the energy is moved rather than generated. That ratio is the Coefficient of Performance (COP), and it is what makes the running-cost comparison work at all.
The running-cost comparison
Using typical 2026 UK business energy rates — around 25p/kWh for electricity and around 7p/kWh for gas — the comparison per unit of useful heat delivered looks like this:
| Heat source | Efficiency | Cost per kWh of heat |
|---|---|---|
| Direct electric heating | 100% | ~25p |
| Gas boiler (real-world) | ~85% | ~8.2p |
| Air conditioning in heating mode (COP 3.0) | 300% | ~8.3p |
| Air conditioning in heating mode (COP 4.0) | 400% | ~6.3p |
Two conclusions worth taking seriously, because a lot of marketing on this subject overstates the case:
- Against gas, a well-maintained heat pump is roughly at parity to modestly cheaper. Anyone promising you a 60% heating bill reduction against a working gas boiler is selling, not calculating.
- Against direct electric heating, it is not close. If you are heating offices, back-of-house areas or a warehouse mezzanine with electric heaters, your air conditioning will do the same job for roughly a quarter of the cost.
Where the real commercial gains sit
Because the gas comparison is close, the case for using your air conditioning in heating mode usually rests on the things that sit around the fuel cost:
- Zonal control. A boiler heats the whole circuit. A VRV system heats the three rooms that are occupied on a Friday afternoon and leaves the rest alone. In part-occupied buildings this is where the money actually is.
- Heat recovery. On a VRV/VRF heat recovery system, heat extracted from a server room or a south-facing meeting room is moved to the cold north side of the building rather than dumped outside. You get that heat effectively free.
- One system, one maintenance contract. Using existing plant for heating removes the cost and compliance burden of maintaining a separate gas system.
- Carbon reporting. As the grid decarbonises, electric heat improves your reported emissions every year without you doing anything. Gas does the opposite.
- Building regulations. Where you are refurbishing or replacing plant, Part L increasingly pushes new heating provision away from fossil fuels. Read more in our guide to compliance.
What determines whether it works in your building
Heating mode is not automatically the right answer everywhere. The honest checklist:
- Equipment age and condition. A neglected system with low refrigerant charge and blocked coils will not achieve a COP of 3.5. It might not achieve 2. Efficiency is entirely dependent on condition.
- Outdoor temperature. COP falls as ambient temperature drops. Modern inverter systems still deliver useful heat well below freezing, but performance on the coldest days of the year is not the performance you see in October.
- Defrost cycles. Outdoor coils ice up in cold, damp conditions and the unit periodically reverses to clear it. Correctly commissioned, this is a minor overhead. Badly set up, it is a comfort complaint every winter.
- Emitter suitability. Air conditioning delivers warm air, not radiant heat. In high-ceilinged warehouse space, destratification or a different approach may be a better answer than simply switching to heating mode.
- Ventilation. Heating a building you are also over-ventilating wastes the saving. Where heating and ventilation are addressed together, the numbers improve considerably.
The maintenance point that decides the outcome
Every figure in the table above assumes a system in good condition. Winter operation puts different demands on equipment than summer operation, and systems that have only ever been serviced for cooling frequently develop faults the first time they are asked to run in reverse in earnest.
Before you rely on air conditioning as your winter heating, it needs a proper pre-season service: refrigerant charge verified, coils cleaned, defrost operation checked, controls configured for heating setpoints and time schedules rather than left on a summer profile. That is standard on an AKS planned maintenance contract, and it is the difference between the 8p figure and the 12p one.
Get an honest answer for your building
AKS Air Conditioning has 34+ years of experience designing, installing and maintaining commercial systems across the North West and nationally, for clients including Deichmann, Footasylum, B&M, AO and Fitness First. As Daikin and Mitsubishi partners, we work with heat pump technology every day — and we will tell you plainly if your existing plant is not the right way to heat your building.
If you want to know what your air conditioning would actually cost to run in heating mode this winter, we will survey the system, check its condition and give you the figures for your building rather than a generic estimate.
Call AKS Air Conditioning on 01704 833 755 or get in touch here to arrange a pre-winter system review.
