--- title: "What Does Air Conditioning Cost to Run? | R.K Plumbing & Heating" description: "What air conditioning costs to run, how to work it out from your own unit and tariff, and why heating with it can cost less than electric heaters." canonical: "https://www.rkplumbingandheatingservices.com/blog/what-does-air-conditioning-cost-to-run" last_updated: "2026-08-20T22:31:45.872Z" --- # What Does Air Conditioning Cost to Run? PublishedMonday, 17 August 2026 What air conditioning costs to run comes down to three things: how much electricity the unit draws, how long it runs for, and what you pay per unit of electricity. None of those are the same from one house to the next, which is why any single headline figure would be wrong for almost everybody. Here is how to work it out for your own system instead. ## The arithmetic Running cost for any electrical appliance is: **power drawn (kW) × hours running × your electricity unit rate (p per kWh)** To fill that in you need two numbers: - **The power input.** This is on the data plate on the unit and in the manual. Look for _power input_ or _rated input_ in kW, not _cooling capacity_ or _output_, which is a different and much larger figure. Mixing the two up is the most common reason people badly overestimate what their system costs. - **Your unit rate.** This is on your latest electricity bill, in pence per kWh. As a worked example, a unit drawing 0.7 kW, running for four hours, on a tariff of 25p per kWh, comes out at 0.7 × 4 × 25 = 70p for that session. Put your own figures in and you have a real number rather than a guess. > The headline figure on the box is the heat the unit moves, not the electricity it uses. They are not the same thing. ## Why the rated figure is not what you will actually pay Almost every system fitted now is an inverter unit. Rather than switching on and off at full power, it modulates: it works hard to pull the room to temperature, then throttles right back to hold it there. Most of the time it is running well below its rated input. That has two practical consequences. Steady running is cheaper than letting a room drift and then hauling it back. And the first hour after switch-on will always cost more than the hours that follow it. ## Heating usually costs less than people expect This is the part that surprises most people. A reverse-cycle system does not make heat, it moves it, so for every unit of electricity it draws it can deliver several units of heat. That is why heating a room with air conditioning generally costs considerably less than heating the same room with a plug-in electric heater, which can only ever give you one unit of heat for one unit of electricity. For a garden office, a loft conversion, or a room the central heating has never quite reached, that changes the sums a great deal. We have written separately about [using air conditioning to heat as well as cool](/blog/can-air-conditioning-heat-your-home). ## What makes the biggest difference - **Where you set it.** Every degree lower in summer, or higher in winter, costs more. Picking a sensible temperature and leaving it alone beats chasing extremes. - **How well the room holds temperature.** Glazing, insulation and how much sun the room takes matter more than the unit does. A conservatory will always cost more to hold at temperature than an internal bedroom. - **Whether the system is sized correctly.** An undersized unit runs flat out and never quite gets there. An oversized one short-cycles. Both cost more to run than a correctly sized system, which is the main reason we survey before quoting. - **Clean filters.** A blocked filter makes the unit run longer for the same result. It is the easiest saving available, and it is free. - **Only conditioning the rooms in use.** With a multi-split, each indoor unit is controlled separately, so there is no reason to be cooling rooms nobody is sitting in. ## Running cost and installation cost are different questions Worth keeping the two apart when you are budgeting. What a system costs to fit is a one-off, and depends on the unit, the pipe run, the electrical supply and the standard of finish. We have covered that in [what air conditioning costs to install](/blog/how-much-does-air-conditioning-cost-uk). ## Getting the sizing right in the first place The single biggest lever on running cost is a decision made before anything is fitted: choosing the right capacity for the room it is going in. That is what a survey is for. R.K Plumbing & Heating are based in Woodingdean and install and maintain air conditioning across Brighton, Hove, Worthing, Lewes, Shoreham-by-Sea, Haywards Heath, Seaford, Burgess Hill and surrounding Sussex towns. If you would like us to look at a room and talk through what it would cost to run as well as to fit, call 01273 911551 or have a look at our [air conditioning installation](/services/air-conditioning-installation) page. From the blog ## Recent articles [All articles](/blog) [ 4 min ### Can Air Conditioning Heat Your Home? ](/blog/can-air-conditioning-heat-your-home)[ 3 min ### How Often Should Air Conditioning Be Serviced? ](/blog/how-often-should-air-conditioning-be-serviced)[ 4 min ### Do You Need Planning Permission for Air Conditioning? ](/blog/do-you-need-planning-permission-for-air-conditioning)