Electricity cost calculator
Enter an appliance's wattage, how many hours a day it runs and your electricity price to see the energy used, the cost for the period and the annual cost.
Uses the rated wattage; variable-speed and standby consumption are approximated.
How this calculator works
Electricity is billed in kilowatt-hours (kWh). One kWh is 1,000 watts used for one hour, so an appliance's cost is its power rating in kilowatts, times the hours it runs, times the price per kWh. A 1,500 W space heater running 4 hours a day uses 6 kWh a day; at $0.15 per kWh that is $0.90 a day, around $27 a month.
Heating and cooling appliances dominate household bills because they run for long periods at high wattage. A 60 W television watched 4 hours a day uses 0.24 kWh — under 4 cents. The same logic explains why switching an old incandescent bulb for an LED saves real money: an 8 W LED replacing a 60 W bulb for 5 hours a day saves 0.26 kWh a day, or about 95 kWh a year per bulb. Use the appliance's actual label rating; some devices draw less than the label suggests in normal use, and older appliances often draw more.
The formula
kWh = (watts / 1,000) × hours/day × days
cost = kWh × price per kWh
per day = cost / days
per year ≈ cost per day × 365For a 1,500 W appliance used 4 h/day for 30 days at $0.15/kWh: 6 kWh/day × 30 = 180 kWh, and 180 × $0.15 = $27.00.
Worked example
A 1,500-watt appliance used 4 hours a day for 30 days consumes 180.0 kWh. At 0.15 per kWh that costs $27.00 for the period — about $0.90 a day and $329 a year at the same usage.
Common mistakes
- Using the maximum wattage for a variable appliance. Fridges, heat pumps and laptops cycle on and off; average draw is lower than the peak rating.
- Forgetting standby power. Devices on standby can draw 1–10 W continuously, which adds up across a house.
- Ignoring time-of-use tariffs. If your price changes by hour, run heavy appliances off-peak and calculate with the applicable rate.
Frequently asked questions
How much does it cost to run a 1,500 W heater?
At 4 hours a day and $0.15/kWh, it uses 6 kWh a day and costs $0.90 — about $27 a month and $328 a year at that usage.
How many kWh does a refrigerator use?
A typical modern fridge uses about 1–1.5 kWh a day, so 30–45 kWh a month. Older appliances can use noticeably more.
How do I read my electricity meter?
Your bill shows kWh consumed and the price per kWh, which may include several components. Divide the total bill by the kWh used to get the effective all-in rate to enter here.
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