How much does air conditioning cost to run?

An air conditioner doesn’t “make cold”: it moves heat from inside to outside. For every kWh of electricity it removes several kWh of heat, depending on its efficiency. In real seasonal use — cycling on and off, very hot days — an old unit achieves about 2.3 and a recent inverter about 3.8.

What a summer costs

Take a 12,000 BTU unit (3.5 kW of cooling) used 6 hours a day for 90 days, at half power on average: it removes about 945 kWh of heat from the room.

• Old unit: about 410 kWh a season — roughly €111, £107 or $74 at typical prices of €0.27, £0.26 or $0.18 per kWh.
• Recent high-efficiency inverter: about 250 kWh a season — roughly €67, £65 or $45.

Habits that matter

• Set 26–27 °C (79–81 °F): every degree cooler adds roughly 6–8% to consumption.
• Use dry / dehumidify mode on muggy but not scorching days: more comfort for less energy.
• Close blinds and curtains during sunny hours: heat that never gets in doesn’t need removing.
• Clean the filters every 2–3 weeks in summer.
• Don’t keep switching an inverter off and on: it works best at a steady low output.

Is it worth replacing?

If your unit is over 10 years old and you use it every summer, a modern inverter saves money — and in winter it can heat as a heat pump, often more cheaply than a gas boiler. The calculator estimates the saving for your home and climate; see inverter air conditioners on Amazon in your country.