How to use it
- Enter the power in watts. Look on the appliance label or rating plate — for example 1500 for a typical heater, 60 for a light bulb, or 2000 for a kettle. If the label only shows kilowatts, multiply by 1000 (1.2 kW is 1200 W).
- Enter the hours used per day. How long the device runs on an average day, e.g. 4 hours. You can use decimals — 0.5 for thirty minutes.
- Enter your price per kWh. This is the unit rate from your electricity bill, in your own currency, e.g. 0.15. Leave it blank to see just the energy used.
- Read the results. The cards show the kWh per day the appliance uses and the running cost per day, per month (30 days) and per year (365 days).
Every card recalculates the instant you change a number, so you can compare appliances or usage habits without pressing a button.
The formula behind the numbers
Electricity is billed by the kilowatt-hour (kWh) — the energy of a 1000-watt device running for one hour. To find an appliance’s daily energy use, the calculator converts watts to kilowatts and multiplies by the hours per day:kWh per day = watts ÷ 1000 × hours. The cost is simply kWh × price per kWh. A 1500-watt heater used 4 hours a day uses 1.5 × 4 = 6 kWh; at a price of 0.15 that is6 × 0.15 = 0.90 per day, about 27 per month and 328.50 per year.
Why it helps to know running costs
- Spot the energy hogs: heaters, kettles, dryers and air conditioners draw far more power than phones or LED bulbs — the per-year figure makes the gap obvious.
- Decide on upgrades: compare an old appliance against a more efficient model by entering each one’s wattage and the same hours.
- Cut your bill: see how trimming an hour of daily use, or switching off standby loads, changes the yearly total.
- Budget with confidence: add up the yearly cost of the things you use most to understand where the bill comes from.
Remember the estimate assumes the appliance draws its rated power the whole time it is on. Devices that cycle on and off — like fridges, thermostats and ovens — use less than their peak rating over a full day, so treat their figures as an upper bound. Motors and heaters can also briefly spike above their label when they start up.
Is it private?
Yes. The Electricity Bill Calculator is plain JavaScript that runs entirely inside your browser tab. The wattages, hours and prices you type are never uploaded, logged or stored anywhere — there are no accounts and no tracking of your inputs. Once the page has loaded you can even use it offline.
Frequently asked questions
My appliance is rated in kilowatts (kW), not watts — what do I enter?
Multiply the kilowatts by 1000 to get watts. A 2.4 kW appliance is 2400 W, and a 0.8 kW one is 800 W. Then enter that number in the power field.
What currency does it use?
Whatever you like. The calculator is currency-neutral: it just multiplies the energy by the price you type, so the cost cards come out in the same currency as your price per kWh.
Why might my real bill differ from this estimate?
Bills can include fixed standing charges, taxes, tiered or time-of-use rates, and appliances that don’t run at full power continuously. This tool estimates the energy cost of one device at a steady rate, which is ideal for comparisons but not a substitute for your itemised bill.
Estimates assume steady power draw and a flat per-kWh price; check your bill for standing charges and tiered rates.