Electricity Cost Calculator — Appliance Running Cost
Work out what an appliance costs to run per day, month and year from its wattage, hours of use and your electricity rate. Free, 100% in your browser.
🔒 Calculated in your browser — nothing is uploaded. You enter your own tariff, so no live-rate lookup is needed. Month = ×30, year = ×365.
What an appliance costs to run
Enter a device's power in watts, how many hours a day you use it, and your electricity rate per kWh. The tool multiplies them into daily, monthly and yearly cost, plus the kWh it uses per day. Useful for space heaters, air conditioners, PCs, fridges, EV charging and more.
Why it needs no live data
You enter your own tariff, so there's no need to look up live rates — the result stays accurate for your bill and everything runs in your browser. Monthly figures use 30 days and yearly use 365; adjust the hours to model seasonal use.
Watts, kilowatt-hours and the tariff
Watts are a rate — how fast a device draws power. A kilowatt-hour is an amount: one kilowatt drawn for one hour, and the unit your bill is priced in. The conversion is the whole calculation: watts ÷ 1000 × hours gives kilowatt-hours, and that times your rate gives the cost. A 2,000 W heater run for three hours is 6 kWh; the same 6 kWh is a 100 W fridge compressor running for sixty. The tariff is yours to enter because rates differ by supplier, region, time of day and season, and a calculator that guessed one would be wrong for almost everybody.
Nameplate watts are not what it draws
The figure on the label is usually maximum draw, and most appliances spend most of their time well below it. A fridge is rated for its compressor but the compressor cycles; a washing machine's peak is the heating element, which runs for a fraction of the cycle; a laptop charger rated 65 W draws that only while charging hard. For anything that cycles, an energy label's annual kWh figure divided by 365 is a better daily input than the nameplate. Standby matters more than it looks: a few watts left on all year is tens of kilowatt-hours. This page treats a month as 30 days and a year as 365, so the monthly figure is a level month rather than a calendar one.
Frequently asked questions
How do I calculate the cost to run an appliance?
kWh = watts ÷ 1000 × hours per day, then cost = kWh × your rate. A 100 W device for 5 h/day at $0.15/kWh is about $2.25 a month.
Where do I find an appliance's wattage?
On the rating plate — the sticker on the back or underside — or in the manual, printed in watts (W) or as amps × volts. For anything that cycles on and off, prefer the annual kWh figure from the energy label: divide it by 365 and enter that as a day of running at one hour.
Is a month 30 days here?
Yes, and a year is 365. The monthly figure is a level month so that twelve of them and one year agree closely, rather than tracking the calendar.
Why is my bill higher than this?
A bill is every appliance plus standing charges, taxes and often a tiered rate where later units cost more. This tool prices one device at one flat rate — useful for comparing two appliances or deciding whether something is worth switching off, not for predicting a bill.