How Much Does It Cost to Run an Air Conditioner for 24 Hours?

With more UK households considering air conditioning, one of the biggest concerns is the cost of running it continuously. While most people only use air conditioning for a few hours at a time, it is useful to understand the potential 24-hour running cost. This helps homeowners in Hampshire, Berkshire, Surrey, and Oxfordshire decide whether air conditioning is a practical option, particularly for bedrooms or open-plan family spaces.

Understanding the Basics

The cost of running an air conditioner for 24 hours depends on:

• Size of the unit (kW capacity): Larger systems consume more energy.
• Efficiency (SEER/SCOP ratings): High efficiency systems use less electricity for the same output.
• Building characteristics: Insulation, glazing, and shading all influence demand.
• Local electricity tariff: The average UK rate in 2025 is around 28p per kWh.
• How the system is used: Inverter-driven compressors rarely run at full load all day.

Calculating the Cost

Let’s take three common residential scenarios.

Bedroom Unit (2.5 kW split)

Power draw: around 0.7 kW.
Cost per hour at 28p per kWh: about 20p.
24-hour running cost: £4.80.

Family Room Unit (5 kW split)

Power draw: around 1.5 kW.
Cost per hour: about 40p.
24-hour running cost: £9.60.

Kitchen Diner Unit (7 kW split)

Power draw: around 2.2 kW.
Cost per hour: about 60p.
24-hour running cost: £14.40.

These figures assume continuous full load. In reality, inverter systems reduce their output once the set temperature is reached, so actual costs may be 30 to 40 percent lower.

Practical Example

A homeowner in Reading runs a 2.5 kW bedroom unit through a particularly hot summer weekend. The system is switched on at midday Saturday and left running until midday Sunday. While the theoretical cost is £4.80, in practice the system modulates down overnight when the outside air is cooler. The actual electricity used may be closer to 12 kWh, costing about £3.35 for the 24-hour period.

What About Running Multiple Units?

In towns like Winchester or Wokingham, larger homes often have several splits. Running three units for 24 hours at the same time would theoretically cost around £29. In practice, careful zoning means you would rarely need them all on full power continuously.

For example, bedrooms may run overnight, while the kitchen diner and lounge are used during the day. This keeps daily costs much lower than the headline figure.

Comparing with Other Appliances

To put costs into context:

• A tumble dryer may use around 5 kWh per cycle, costing £1.40.
• An electric oven running for two hours can use 3 kWh, costing about 84p.
• A modern air conditioner cooling a bedroom overnight can cost less than running the tumble dryer once.

Cost in the Context of Comfort

In areas like Basingstoke or Guildford, where summer nights can become uncomfortable during heatwaves, many households are now willing to accept the modest running cost for the benefit of restful sleep. Being able to keep bedrooms cool during a hot spell adds significant value to quality of life.

Reducing the 24-Hour Cost

Homeowners can take simple steps to keep costs manageable:

• Set realistic temperatures: 22°C is more efficient than 18°C.
• Use timers and sleep modes: Ensure the system runs only when needed.
• Improve insulation: Keeps cool air inside for longer.
• Close blinds on sunny sides: Reduces solar gain.

Installers like ClimateWorks design systems with zoning in mind, ensuring energy is only used where it delivers real benefit.

The Bigger Picture

While a headline figure of £5 to £15 for 24 hours might sound high, the reality is that most UK households do not run air conditioning non-stop. With inverter technology and good zoning, actual costs are often half the theoretical maximum. For many homeowners in Hampshire, Berkshire, Surrey, and Oxfordshire, the comfort gained is well worth the modest expense.

References

• Ofgem, Electricity prices and tariffs 2025 – Ofgem
• Energy Saving Trust, Energy consumption of household appliances – Energy Saving Trust
• Mitsubishi Electric UK, Air Conditioning Efficiency – Mitsubishi Electric

About the Author

Dr. Julian Carter – Technical & Compliance Director, ClimateWorks

Dr. Julian Carter is a recognised specialist in building services engineering with over 25 years of experience in ventilation, refrigeration, and air conditioning. As Technical & Compliance Director at ClimateWorks, he advises on best practice for system design, installation, and maintenance across residential and commercial projects in Hampshire, Berkshire, Surrey, and Oxfordshire. He also lectures part-time at a leading UK university, sharing his expertise with the next generation of engineers.

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