How to Reduce Air Conditioning Electricity Use During a Heatwave

Air conditioning uses less electricity when the room gains less heat in the first place. Close external shading, blinds, curtains, or shutters before strong sun reaches the glass where practical; reduce unnecessary heat from cooking, lighting, and electronics; and close doors to rooms you are not cooling. Ventilating at cooler times may help in some homes, but windows should not be left open while a portable or split air conditioner is actively trying to cool the same space. The right approach depends on outdoor temperature, humidity, safety, and the home's ventilation needs.

Choose a realistic comfort setting and avoid repeatedly changing it in response to a hot afternoon. Lowering a thermostat far below the temperature you actually need can extend compressor run time without making a room cool instantly. Use timers, sleep modes, and room-by-room operation where they fit the household. Keep filters clean and make sure portable units have an effective exhaust path; restricted airflow, a poorly fitted window kit, or equipment that is too small for the heat load can make an appliance run longer than expected.

Track the energy rather than guessing from the weather. A plug-in energy meter may help with compatible portable equipment, while a smart meter or electricity account can show total household kWh. Compare one hot-period day with a similar day without cooling where possible, then use the difference as an input to the UK Energy Bill Calculator. This separates added cooling consumption from fixed charges or a tariff change and gives a more useful monthly estimate than a national average alone.

If you have a time-of-use tariff, identify whether the hours you need cooling overlap with a higher-priced period. Safety and comfort come first during dangerous heat, so do not turn off essential cooling solely to avoid a peak rate. Instead, reduce the room's heat gain before the peak period and move flexible loads such as laundry or EV charging when the tariff permits. Check the supplier's current schedule and eligibility rules rather than assuming an advertised off-peak rate applies.

The European Environment Agency notes that heatwaves increase the need for cooling while making building efficiency and passive cooling important. This guide is an energy-use checklist, not heat-health, ventilation, electrical, or building advice. Seek appropriate support for people at higher risk from heat, and consult a qualified professional before changing fixed cooling equipment, electrical circuits, or a building's ventilation arrangement.

For a useful comparison, keep the period, units, and assumptions consistent across each option. Use a calculator to explore the figures, then rely on current documents from the relevant provider or authority for terms that apply to your home.

What to check next

Use the related calculator or guide to compare the assumptions that matter for your home, then confirm any tariff, quote, or program term with the relevant provider or authority.