Start with the unit’s power draw and how long it runs. The room and the temperature you set also affect energy use.
The simple sum
Energy use (kWh) = power the unit draws (kW) × hours of use
A typical single-room unit might draw around 0.5 to 1 kW while it’s working hard, and much less once the room has reached temperature. Total energy use depends on how long it runs.
A real-world example
In one example we’ve seen, air conditioning ran overnight in five bedrooms. The units’ total energy use depends on how long each one runs and the temperature set in each room.
What changes the cost
- The temperature you set. The set point affects how hard the unit works. In summer, a higher set point changes how long the unit needs to cool the room. In winter, the heating set point affects run time too.
- How efficient the unit is. Look for a high SEER for cooling and a high SCOP for heating.
- Your home. Insulation, window size and which way the room faces all matter.
- Your tariff. Ask your electricity supplier which tariff applies to the hours you use the unit.
Work out your own
Find the unit’s rated power input on its specification sheet and multiply it by the hours you expect to run it to estimate energy use in kWh. Your electricity tariff determines what that energy costs; check the rate with your supplier.