Air-to-air heat pumps in Dartford
Think of an air-to-air heat pump as the air conditioner you were going to buy anyway, used in January as well as July. Across Dartford we fit them in all-electric flats, in loft rooms the radiators barely warm, and in extensions that are freezing in winter and stifling in summer. One unit, two seasons, and the boiler keeps the taps hot.
Price a heat pump
Three details and we call you back with the next step.
- About four units of heat per unit of electricity
- No gas needed in the room
- The boiler keeps doing the hot water
Where does the heat come from on a cold day?
From the air itself, which holds usable energy well below the temperatures that feel cold to us. The refrigerant in the outdoor coil absorbs that energy even at 2°C; the compressor then squeezes the refrigerant until it is hotter than the room, and the indoor coil hands the warmth over. Flip a valve and the whole cycle runs backwards for summer. The electricity is spent moving heat rather than making it, which is how the unit puts out more warmth than the power it draws.
How do the running costs compare?
| Where the warmth comes from | Price of a kilowatt-hour of heat |
|---|---|
| Fan heater, oil radiator or panel heater | 26.32p |
| Gas boiler | 7.97p for the gas, with the boiler's losses on top |
| Air-to-air unit at a seasonal efficiency of 4 | Roughly 6.6p |
The unit rates are the Ofgem price cap for October to December 2026, which resets every three months, and your own tariff may be different. The efficiency of 4 is the Energy Saving Trust's description of typical seasonal performance; what you get depends on the unit, the room and the weather outside. Against electric heaters the gap is enormous. Against gas it is small. Sources: Ofgem; Energy Saving Trust.
Can it take over from the boiler?
Not for hot water, and not for the whole house. The Energy Saving Trust notes that air-to-air systems are not normally designed to supply hot water, so showers and taps stay with the boiler or the cylinder. What the unit heats is the air in the room where its indoor unit hangs. It is the most efficient room heater you can buy, not a replacement for a central heating system across four bedrooms.
Who in Dartford gets the most out of one?
- Homes heated by electricity alone, often with storage or panel heaters: the 2021 Census counted 3,830 in the borough.
- Lofts and rear extensions at the cold end of a radiator circuit.
- Anyone who was going to fit cooling anyway, for whom the heating comes at no extra cost.
- Garden offices with no heating of their own.
The winter is mild here, but not without frost: Greenwich Observatory, our nearest Met Office station, averages about 23 nights of air frost a year, so a unit relied on for heating is sized for the cold mornings as much as the hot afternoons. The full year is charted on our air conditioning in Dartford page. Sources: Census 2021; Met Office.
Why does running it as a heater help with planning?
Because the rules were rewritten with heat pumps in mind. Since 29 May 2025 the permitted development right for a heat pump on a house in England requires that the unit is not used solely for cooling, which an air-to-air unit set up for heating satisfies and a cooling-only unit cannot. The same change lifted the size limit on a house to 1.5 cubic metres and dropped the requirement to keep the unit a metre from the boundary. Flats, listed buildings and road-facing walls in a conservation area still have their own conditions, which the planning guide sets out. Sources: SI 2025/560; Baxi; Planning Portal.
Questions people ask
What happens in a frost?
It keeps heating, with less output, and it stops for a few minutes now and then to defrost its outdoor coil. A unit chosen as the main heat source is sized with those cold mornings in mind.
Does the government grant apply to this?
The grant scheme is designed around air-to-water heat pumps that feed radiators and a hot water cylinder. Ask us what applies to your house and we will tell you only what we can confirm.
Will it heat the landing as well as the bedroom?
Not through a closed door. A multi-split puts an indoor unit in each room you want heated, all fed from one outdoor unit.
Sources we checked
- Ofgem: price cap unit rates and standing charges, October to December 2026
- Energy Saving Trust: an overview of air-to-air heating (slides, 2024)
- Census 2021: type of central heating, Dartford
- Met Office: climate averages for Greenwich Observatory, 1991 to 2020
- legislation.gov.uk: the 2025 amendment to the permitted development order (SI 2025/560)
- Baxi: what changed for heat pump permitted development on 29 May 2025
- Planning Portal: when an air source heat pump on a house or flats is permitted development
Worth knowing before you ring
With these we can usually tell you on the first call whether the job is simple.
- The postcode
- Whether it is a house, a flat or business premises, and roughly its age
- If you rent or lease, who owns the external wall
- Which room, how big, and the direction its window faces
- Any management company, conservation area or listing that applies
Air-to-air heat pumps outside Dartford
Looking for air to air heat pumps in one of the towns around us? Each page below sets out that place's own housing and planning position, and our air conditioning in Dartford page gives the full picture.
Worth reading first
Air conditioning and planning permission: the rules for England
Every permitted development condition in one table, then the twists Dartford's new estates and conservation areas add.
What size of air conditioner does a room need?
Kilowatts and BTU by room size, with the adjustments that matter.
What does air conditioning cost to fit and to run?
Where the money goes: the unit, the labour, the wiring, the electricity, and the extras a flat or a new estate brings.
Jobs that often go with this one
Air conditioning installation
The whole job from the first measurement to the handover of the remote, with every consent checked on the way.
Home air conditioning
The back bedroom, the new flat with the glass wall, the loft nobody can sleep in: cooled in summer, warmed in winter.
Multi-split air conditioning
Several rooms, one box in the garden. The design that fits inside a semi's single permitted outdoor unit.
Conservatory air conditioning
For the glass room that is a greenhouse in July and a fridge in January, and the garden office beside it.
The rest of what we do
Office air conditioning
Offices from a room above a shop to a floor on a business park, with the heat rules and the landlord dealt with.
Commercial air conditioning
Retail and hospitality premises, sized with the door open and the bedroom over the shop remembered.
Server room cooling
Dedicated cooling for the rack, calculated from the wattage on the plugs and running when the office is dark.
Air conditioning servicing
An annual visit for any system by any installer, with the legal leak check where the charge demands one.
Air conditioning repairs
Warm air, a puddle under the indoor unit, ice on the pipes or a blinking code: the cause found before anything is ordered.
Want us to ring you?
A name, a number and a postcode is enough. Say which room if you can. Or ring 01322 952910.