It's the first question almost everyone asks, and the honest answer is that it depends on your home. Two bedrooms of the same size can cost quite different amounts to cool if one is on the ground floor next to the garden and the other is a loft room at the top of a three-storey Victorian house in Malvern. This guide explains what drives the price, what a proper quote should include, and how to estimate running costs yourself.
What decides the installation price
A fitted split system has an indoor unit on the wall of the room and an outdoor unit outside. They're connected by insulated refrigerant pipes, a condensate drain and a control cable. Most of the cost comes from these things:
- The number of rooms. One room needs one indoor and one outdoor unit. Two to five rooms can often share a single outdoor unit on a multi-split system, which costs more than a single split but less than several separate systems.
- The size of each unit. This is set by the room: its floor area, ceiling height, windows and which way it faces. A south-facing loft room needs more cooling than a north-facing bedroom of the same size.
- The pipe run. The distance between indoor and outdoor units, and how the pipes get there, whether straight through a wall, across a loft or down the outside of the house, affects both materials and labour.
- The outdoor unit position. Ground-level bases are simplest. High wall brackets, flat roofs and raised positions in flood-risk areas take more time and equipment.
- Wall construction. Drilling a cavity-brick 1980s semi in Redditch is quicker than going through half a metre of stone in a Broadway cottage.
- Electrics. Most systems need their own circuit from the consumer unit. If your consumer unit is old or full, that adds work.
What a good quote should include
When you compare quotes, check that each one covers:
- The make and model of every indoor and outdoor unit, and their cooling and heating capacities in kW
- Confirmation that the installing business holds the appropriate F-Gas company certification, and that the work includes pressure testing, evacuation and commissioning
- The electrical work, and who certifies it
- The condensate drain route
- Making good the wall where the pipes go through
- Pipe trunking or covers where pipework runs outside
- Registration of the manufacturer's warranty, and what the warranty requires, for example annual servicing
- Any access equipment, such as scaffolding for high walls
Ask whether the price is fixed, when it becomes fixed, and what could change it.
How to work out running costs
Running cost depends on how much electricity the unit draws, how long you run it and what you pay per unit (kWh). You can estimate it like this:
Power drawn (kW) × hours of use × your price per kWh = cost
A modern inverter unit doesn't run at full power all the time. It works hard to bring the room down to temperature, then slows right down to hold it there. For a typical bedroom-sized unit (about 2.5 kW of cooling), the electrical draw once the room is comfortable can be somewhere around 0.2 to 0.6 kW, depending on the model and conditions.
A worked example
Illustrative example, September 2026. Assumptions: a bedroom unit of about 2.5 kW cooling capacity, averaging 0.4 kW of electrical draw once the room is at temperature, run for 8 hours a night, with electricity at 25p per kWh. These are assumptions, not measurements of any particular system or tariff. Check your bill for your actual rate.
| Step | Working | Result |
|---|---|---|
| Energy per night | 0.4 kW × 8 hours | 3.2 kWh |
| Cost per night | 3.2 kWh × 25p | 80p |
| A summer of 30 hot nights | 30 × 80p | £24 |
This shows the method, not a prediction. Real figures depend on the unit's efficiency rating, the room, the weather, how well the room is insulated, the temperature you set and your tariff. A higher target temperature generally means lower running costs.
Heating
A reversible split system is an air-to-air heat pump, so it can heat the rooms it serves as well as cool them. As a heat pump, it can deliver more heat than the electricity it uses, though how much depends on the model and the outdoor temperature. Whether using it for heating saves money compared with your existing heating depends on your fuel prices, tariff and how you use it.
Servicing
You should clean the indoor unit's filters every few weeks when it's in regular use. That's a two-minute job. Some manufacturers' extended warranties require an annual service, so check the warranty terms, so ask about this when you get your quote.
Get a price for your home
The fastest way to a real figure is a survey. Tell us which rooms you'd like to cool and we'll pass your enquiry to an independent local installer, who can contact you about a survey and quotation. There's no obligation. If you're wondering about permission for the outdoor unit, read our guide to planning rules in Worcestershire.