How do I work out the running cost of an appliance?

Cost = power in kilowatts x hours used x price per kWh. A 2000 W (2 kW) heater run 4 hours uses 8 kWh; at a 27p unit rate that is about 2.16 a day. This tool does the maths for every appliance at once and scales it to a week, month and year.

What is a kWh and how does it relate to watts?

A kilowatt-hour (kWh) is the energy used by a 1000 W appliance running for one hour. To get kWh, multiply watts by hours and divide by 1000. Your electricity meter and bill are measured in kWh, which is why the calculator converts wattage and usage time into kWh before applying your price.

What is a standing charge?

A standing charge is a fixed daily fee you pay just to be connected to the grid, regardless of how much electricity you use. It covers network and metering costs. Enter your daily standing charge separately so the yearly total reflects both your usage and this fixed cost.

Where do I find my price per kWh and standing charge?

Both appear on your electricity bill or in your online account, usually under tariff details or unit rates. The price per kWh (sometimes called the unit rate) and the standing charge per day are listed separately. Enter them exactly as shown for an accurate estimate.

Why does days-per-week matter?

Many appliances are not used every day — a tumble dryer or oven might only run a few times a week. Setting days-per-week averages the usage across the whole week so the monthly and yearly figures are realistic rather than assuming daily use.

How accurate is the CO2 estimate?

It multiplies your yearly kWh by the grid carbon intensity in grams of CO2e per kWh. The default is a typical figure, but grid intensity varies by country and time of day, so adjust it to your local value for a closer estimate. It is a guide, not an audited carbon footprint.

Electricity Cost Calculator

The electricity cost calculator turns the wattage of your appliances into real money: it lists every device you own, applies your tariff, and shows exactly what each one costs to run per day, week, month and year. Where a single-appliance tool stops at one gadget, this one adds up your whole home — fridge, kettle, TV, heater, EV charger and more — so you can see your total bill and, crucially, which appliance is quietly costing the most. It is for anyone trying to cut an energy bill, compare a new appliance against an old one, size a solar or battery system, or simply understand where the money goes.

How it works

Electricity is billed in kilowatt-hours (kWh). One kWh is the energy a 1000-watt appliance uses in one hour. The calculator converts each appliance to kWh with the formula:

kWh per day = (watts x quantity x hours per day x days per week / 7) / 1000

It then multiplies your total daily kWh by your price per kWh to get the usage cost, adds your fixed standing charge (a flat daily fee just for being connected to the grid), and scales the result to a week (x7), a month (x365/12) and a year (x365). The days-per-week control averages intermittent appliances — a dryer used three days a week is counted at 3/7 of its daily figure — so the totals stay realistic. Finally it estimates yearly CO2 by multiplying your annual kWh by the grid carbon intensity you enter.

Worked example

Suppose you list three things: a fridge-freezer (150 W, 8 hrs/day, every day), an electric kettle (3000 W, about 18 minutes/day) and a 55-inch TV (90 W, 4 hrs/day). The fridge uses 150 x 8 / 1000 = 1.2 kWh/day, the kettle roughly 0.9 kWh/day, and the TV 90 x 4 / 1000 = 0.36 kWh/day — about 2.46 kWh/day combined. At a unit rate of 27.03p that is 0.66/day in usage, plus a 0.61/day standing charge, giving 1.27/day, roughly 38.65/month and about 464/year. Add an electric heater run 4 hours a day in winter and the yearly figure jumps by well over 200, which is why the chart ranking appliances by annual cost is so useful for deciding what to switch off.

Formula reference

Quantity	Formula
Energy per appliance	kWh/day = watts x qty x hrs x (days/7) / 1000
Usage cost	total kWh/day x price per kWh
Daily total	usage cost + standing charge
Monthly cost	daily total x 365 / 12
Yearly cost	daily total x 365
CO2 per year	yearly kWh x grid intensity (g/kWh) / 1000

Power factor and surge/idle draw are ignored — nameplate wattage is treated as steady-state, which is the standard assumption for resistive and most household loads. Every figure is calculated in your browser; no numbers are ever uploaded or stored on a server.