How it is calculated
kWh per day = watts × hours × quantity ÷ 1000 Monthly cost = kWh per day × 30 × price per kWhWattage is on the appliance label. Compressor appliances (fridge, AC) do not run at full power all the time, so enter approximate actual running hours.
Many utilities use tiered tariffs; use your average price from your bill.
Worked example
A 1,500 W air conditioner running 8 hours a day: 1,500 × 8 ÷ 1000 = 12 kWh a day, 360 a month; at 1.2 per kWh = 432 a month.
Frequently asked questions
How do I find my price per kWh?
Divide the energy charge on your bill (before fixed fees) by the kWh used.
Does standby use power?
Yes, a little (1–5 W per device), but it adds up over a year.
What uses the most?
Air conditioners, water heaters, electric ovens and heaters.