Use the calculator and worked examples to estimate the electricity cost for one to five active rooms. Choose the average cooling capacity of the indoor units, then adjust the tariff and expected usage.
This calculator asks for the average cooling capacity of the indoor units because that is the size customers normally recognise, such as 2.5 kW. It then estimates electrical input using an illustrative EER of 3.3. Actual inverter consumption changes continuously with demand.
Assumption: 2.5 kW average cooling capacity per active room, converted to approximately 0.76 kW electrical input using an illustrative EER of 3.3; six hours per day, 30 days, at 26.11p/kWh. All rooms are assumed to be active for the full period.
This is a planning estimate rather than a promise of consumption. Inverter systems normally reduce compressor input after rooms approach the set temperature, while very hot rooms, low setpoints, poor insulation, open doors or undersized equipment can increase demand.
Loft rooms, south-facing glazing, flat roofs and garden rooms can create much higher cooling loads.
A moderate setpoint normally requires less energy than trying to make the room extremely cold.
Running one bedroom at night is different from cooling five rooms throughout the day.
SEER, part-load performance and the selected indoor/outdoor combination affect seasonal consumption.
Insulation, shading, blinds, glazing and air leakage influence how quickly heat enters the room.
Clean filters and unobstructed coils help preserve airflow and heat-transfer performance.
A unit described as 2.5 kW delivers approximately 2.5 kW of nominal cooling capacity; it does not continuously consume 2.5 kW of electricity.
The calculator divides cooling capacity by an illustrative EER of 3.3. A 2.5 kW unit therefore uses approximately 0.76 kW in this rated-condition example.
Estimated input kW × operating hours × £ per kWh gives the simple electricity-cost estimate.
An inverter system ramps up and down. Product-specific power-input data and post-installation monitoring give a more accurate answer.
Close blinds or curtains before strong sun heats the room.
A stable comfortable temperature is usually more efficient than extreme cooling.
Use zoning and schedules instead of cooling every room automatically.
Do not continually replace cooled indoor air with hot outside air.
Restricted airflow can reduce performance and comfort.
Maintaining a sensible temperature can be easier than recovering a room after it becomes extremely hot.
Tell us the room sizes, glazing, property type and expected usage. We can recommend capacities and provide product-specific efficiency information rather than relying on a generic calculator assumption.
Multiply the unit electrical input in kW by the hours used and your electricity tariff. A 0.5 kW average input used for six hours at 26.11p/kWh costs about 78p for that day.
Not necessarily. It depends on how many rooms are active, their heat loads and the outdoor-unit combination. The calculator provides a simple active-room estimate rather than a system design prediction.
Normally no. Inverter systems reduce output after the room approaches the set temperature. Very hot weather, low setpoints, open doors or undersized equipment can keep demand higher.
Daytime solar generation can offset some air-conditioning electricity use when generation and cooling demand occur together. The amount depends on the solar system, household load and export arrangements.
Ofgem energy price-cap rates are reviewed quarterly. Calculator defaults should be updated when the tariff reference period changes.
