Electricity Cost Calculator
Work out what any appliance costs to run per day, month and year from its wattage, hours of use and your electricity rate per kWh.
The formula
kWh/day = watts × hours ÷ 1000 · cost = kWh × rate per kWh
A kilowatt-hour is what a 1,000 W appliance uses in one hour — it's the "unit" on your electricity bill.
Worked example
A 1,500 W air conditioner running 4 h/day at 0.15 per kWh: 1,500 × 4 ÷ 1000 = 6 kWh/day →
0.90/day, 27.00 per month, about 328 per year. Running it one hour less per day saves ~82 a year.
Typical appliance wattages
| Appliance | Typical power |
|---|
| LED bulb | 10 W |
| Wi-Fi router | 10 W |
| TV (LED, 50″) | 100 W |
| Fridge (average draw) | 150 W |
| Desktop PC | 200 W |
| Washing machine (cycle avg) | 500 W |
| Microwave | 1,000 W |
| Air conditioner (1.5 t) | 1,500 W |
| Electric kettle | 2,000 W |
| Water heater/geyser | 2,500 W |
Heating and cooling dominate most bills — the big wins are AC/heater hours, water heating and, for always-on
devices, standby power (a smart plug or power strip fixes that).
Frequently asked questions
How do I calculate an appliance’s electricity cost?
kWh per day = watts × hours per day ÷ 1000; cost = kWh × your rate per kWh. A 1,500 W AC running 4 hours uses 6 kWh a day — at 0.15/kWh that’s 0.90 per day, about 27 per month.
Where do I find my rate per kWh?
On your electricity bill — divide the total charge by the kWh billed for a real-world average that includes fixed charges and taxes, or use the listed per-unit tariff for the marginal rate.
Do appliances use power when switched off?
Many do — standby ("vampire") power. TVs, consoles and chargers can draw 1–10 W continuously, which across a household is commonly 5–10% of the bill. Anything warm when "off" is drawing power.
Why is my fridge’s cost lower than its rated wattage suggests?
Compressors cycle on and off, so a fridge rated 150 W might average 40–60 W over a day. For cycling appliances, use an average draw or a plug-in energy meter for accuracy.