Use the air conditioner's electrical input or measured kWh to calculate its running cost. Cooling capacity in BTU/h or thermal kW is not the same as electrical input power. An inverter unit can vary its draw, so connected hours multiplied by its maximum input can overstate ordinary consumption.
Calculate cooling or heating energy
Open the running-cost calculator. Enter measured kWh/day if available. Otherwise use the documented electrical input and equivalent full-power hours, stating the assumption. Calculate cooling and heating separately if their input ratings and usage differ.
A hypothetical 1.2 kW electrical input running at that draw for six hours uses 7.2 kWh. Over 30 days that is 216 kWh, or R756 at illustrative R3.50/kWh. At an average measured draw of 0.6 kW over those same six hours, energy would be 108 kWh/month and R378. Neither example is a promise for a particular model.
Read input, output and efficiency correctly
Look for the manufacturer's electrical input under the intended operating mode. A headline cooling-capacity number describes heat moved, not electricity consumed. Maximum input can help establish an upper operating scenario but does not describe every hour of a modulating unit.
Compare energy labels and manufacturer test conditions for similar products. A room's heat gain, installation, maintenance and chosen settings affect actual operation. An efficiency rating helps compare specified conditions; it does not replace an electricity measurement in your home.
Measure a representative operating pattern
Measure over several comparable days and record hours, settings, room conditions and occupancy. Include the whole system's electrical consumption where the measurement arrangement permits. Do not read only an indoor display and assume it includes every component unless the manufacturer confirms that scope.
Whole-house meter differences include other loads. A kettle, geyser or pump starting during the test can distort a short comparison. Use appropriately rated installed measurement and qualified assistance where required; do not alter a hardwired circuit to fit an unsuitable plug meter.
Apply the household's energy rate
For a flat rate, multiply measured kWh by the current VAT-inclusive energy charge. For monthly blocks, estimate the extra cost above the rest of the household's tally. The tariff hub distinguishes supported rates, fixed charges and schedules requiring further confirmation.
If your tariff changes by time of use, split energy into the corresponding time periods; this simple calculator does not reconstruct an hourly load profile. Shifting run time saves money only when it changes an applicable charge or actual energy use.
Compare practical changes fairly
Compare the same comfort task: the same room, occupancy and comparable weather. Record a change to the set point, operating period or shading and measure again. A shorter run that leaves the room unusable is not the same service as the original run.
Follow the manufacturer's maintenance instructions and use qualified service for faults. Filter condition, installation and unusual operation belong in the measurement notes. Avoid treating a generic wattage table as evidence that a particular unit is faulty.
Air-conditioner questions
Is a 12,000 BTU unit a 12 kW electrical load?
No. Read its electrical input specification. Cooling capacity and electricity input are different quantities.
Can I use one average daily kWh figure?
Use a measured representative figure and retain the conditions. A different season or operating pattern can need a new measurement.
References: energy-efficiency standards guidance and Eskom household energy guidance. Reviewed 1 November 2026. All numerical examples are stated scenarios.