Running an air conditioning system in the UK doesn't have to be expensive. With the right habits, settings, and maintenance routine, you can stay comfortable year-round while keeping your electricity bills firmly under control. This guide brings together the most effective tips for reducing air conditioning running costs — whether you have a split system, portable unit, or air source heat pump.
1. Set the Right Temperature
The single biggest factor in your air conditioning running costs is the temperature you set. It's a common misconception that setting the unit to its coldest setting will cool the room faster — it won't. It simply forces the unit to work harder for longer, consuming significantly more electricity.
Studies show that running your air con at 25–27°C instead of 18°C can reduce electricity consumption by up to 30%. For most people in the UK, 24–26°C is perfectly comfortable. For heating mode, 18–21°C is the recommended range. Set it and leave it — constantly adjusting the thermostat is one of the most common causes of inefficiency.
2. Use Sleep Timers and Fans Together
Leaving the air con running all night is one of the easiest ways to run up unnecessary costs. Most modern units have a sleep timer or auto-off function — set it to switch off one to two hours after you go to bed. By that point the room will have cooled sufficiently, and a ceiling or desk fan can circulate the remaining cool air at a fraction of the running cost.
If your unit is older and lacks these features, a replacement remote control with timer functionality can unlock them without needing a full unit replacement.
3. Keep the Heat Out Before It Gets In
Reducing the heat load on your air conditioning system is just as important as the unit itself. Heavy curtains, blackout blinds, or external shading can significantly reduce how much solar heat enters a room during the day, meaning your unit has less work to do.
Also check for gaps around doors and windows. Warm air infiltrating through poorly sealed frames forces your system to compensate continuously. Sealing these with draught excluders or insulation tape is a low-cost fix with a meaningful impact on efficiency.
4. Clean and Maintain Filters Regularly
A dirty filter is one of the most common causes of reduced efficiency and increased running costs. Blocked filters restrict airflow, force the unit to work harder, reduce cooling output, and degrade indoor air quality. Clean your filters at least once a month during periods of heavy use, and arrange a full service once or twice a year — ideally before summer.
Regular maintenance also extends the lifespan of the unit significantly, protecting your investment long-term.
5. Don't Block Vents or Airflow Paths
Check that furniture, curtains, or other objects aren't obstructing indoor vents or the outdoor unit. Restricted airflow forces the system to work harder and reduces its efficiency. If your outdoor unit is in direct sunlight, shading it with an awning or cover can also improve performance — an overheating compressor runs less efficiently.
Similarly, avoid closing off too many internal doors. Air conditioning systems are designed to condition a space, not individual rooms. Closing off rooms can create pressure imbalances that reduce overall effectiveness.
6. Reduce Internal Heat Sources
Your air conditioning system has to work against every source of heat in the building — not just the sun. Incandescent and halogen bulbs generate significant heat; switching to LED alternatives reduces both your lighting costs and the heat load on your air con. Electronic devices left on standby also generate heat — unplugging them when not in use makes a small but cumulative difference.
During summer, try to avoid using the oven during the hottest part of the day. Cooking in the evening when temperatures are lower reduces the demand on your cooling system considerably.
7. Use a Programmable or Smart Thermostat
If you're out of the house for long periods, a programmable thermostat allows you to maintain a stable background temperature rather than letting the space heat up and then having to cool it back down rapidly — which is far less efficient. Maintaining a steady temperature uses less energy than repeated large temperature swings.
8. Optimise Usage Timing
Running your air conditioning during the cooler parts of the day — early morning or late evening — means the unit has less temperature differential to overcome and will reach the target temperature faster and with less energy. Pre-cooling a space before the hottest part of the day is often more efficient than trying to cool it down once it has already heated up.
9. Insulate Pipework Properly
For split systems and heat pumps, well-insulated refrigerant pipework between the indoor and outdoor units reduces heat gain and improves system efficiency. If your pipework insulation is degraded or missing, replacing it is a straightforward job. Armaflex EVO pipe insulation is a Class O rated option suitable for air conditioning and refrigeration applications, and K-FLEX ST insulation tape provides a vapour barrier finish for exposed joints.
10. Best Settings for Air Source Heat Pumps
Air source heat pumps operate differently to conventional air conditioning units and have their own efficiency considerations:
- Set the thermostat to 18–21°C for heating — heat pumps work most efficiently at lower flow temperatures over longer periods, rather than short high-temperature bursts
- Set the timer to begin heating at least 2–3 hours before you need it, and reduce the temperature 2–3 hours before bed
- Set the hot water cylinder to 40–50°C for daily use, with a weekly hygiene cycle at 60°C to prevent legionella bacteria growth
- Check and clean filters and coils regularly to maintain airflow and performance
- Use a weather compensation controller if available — this automatically adjusts the flow temperature based on outdoor conditions, which is the most efficient way to run a heat pump
A well-insulated building envelope is essential for heat pump efficiency. The better your insulation, the lower the flow temperature your heat pump needs to maintain comfort — and the lower your running costs.
Frequently Asked Questions
What temperature should I set my air con to save money?
25–27°C for cooling, 18–21°C for heating. Every degree closer to the outdoor temperature reduces energy consumption.
How often should I clean my air con filter?
At least once a month during heavy use, and a full professional service once or twice a year.
Does shading the outdoor unit really make a difference?
Yes. An outdoor unit in direct sunlight has to work harder to reject heat. Shading it can improve efficiency, but ensure airflow around the unit is not restricted.
Is it cheaper to leave the air con on all day or turn it on and off?
For most UK homes, turning it off when the space is unoccupied and using a programmable thermostat to pre-condition the space before you return is more efficient than leaving it running continuously.