How to use it
Pick a mode
Use By watts if you know the device's power and daily hours, or By kWh if you already know its daily energy use. The preset chips fill typical values for common appliances.
Set your price
Enter your price per kWh from your electricity bill. The default of 0.17 is only a placeholder — rates vary widely by country and tariff.
Read the table
The headline shows the monthly cost, and the table breaks down kWh and cost per day, week, month and year.
About the electricity cost calculator
The math is simple — kWh = watts × hours ÷ 1000, cost = kWh × price — but two details matter. First, many devices draw power even when "off": TVs, game consoles, chargers and set-top boxes sip a few watts around the clock. These phantom loads look tiny per device but can add up to a noticeable share of a household bill, which is why cutting standby power is one of the cheapest savings available.
Second, the fridge preset uses 24 hours at 150 W deliberately. A fridge is plugged in all day, but its compressor cycles on and off, so 150 W here represents an averaged draw rather than the peak on its nameplate. For any cycling appliance — fridges, freezers, AC units, heat pumps — an averaged figure over a full day gives a far more realistic cost than the maximum rating.
Questions
How do I find a device's wattage?
Check the label or nameplate on the device itself, or on its power adapter — most list watts directly. If it only shows amps and volts, multiply them: watts = amps × volts. For a measured figure, a cheap plug-in power meter reads real consumption including standby.
Is a month 30 days here?
No — the calculator uses 30.42 days per month, which is 365 ÷ 12. That way the twelve monthly figures add up to exactly one year instead of undercounting by about five days.
Does this include standby power?
Only if you account for it yourself. The calculation covers the watts and hours you enter, so a TV used 4 hours a day but drawing 2 W in standby the other 20 hours uses slightly more than shown. You can add standby as a second calculation or use a measured kWh figure in By kWh mode.
Is anything uploaded?
No. The calculation runs entirely in your browser — nothing is sent to a server, and the tool is free with no sign-up.