The right numbers for your household costs
Free calculators and fact-checked guides: what your appliances really use, what they cost to run, and how much material to buy for your projects. Every figure is sourced.
All our calculators
Tools →Appliance running cost calculator
Enter an appliance's wattage and daily use to get kWh and running cost per hour, day, month and year, using current US, UK or European electricity prices or your own rate.
CalculatorConcrete calculator (slabs, footings, post holes)
Work out how much concrete you need for a slab, footing or round post hole, with a waste allowance, in cubic yards or cubic meters, plus the number of 80 lb or 60 lb bags.
CalculatorPaint calculator for a room
Enter room size, doors, windows, coats and coverage to get the wall area, gallons (or liters) of paint needed and the cans to buy.
CalculatorWatts to amps calculator
Convert watts to amps or amps to watts for 120 V, 230 V, 240 V or three-phase supplies, and work out energy use in kWh. Formulas and worked examples.
DataHow much electricity appliances really use: measured data
Median annual kWh for 36 household appliances, measured every 10 minutes in 100 homes (ADEME, 2023–2024): water heaters, fridges, routers, TVs, washers and more, with running costs.
DataElectricity prices in Europe: country ranking
Average household electricity price per kWh in every EU country plus Norway and Liechtenstein, including all taxes, from Eurostat. Which countries pay the most and the least?
Latest guides
How much electricity does a fridge use?
A fridge-freezer uses about 268 kWh a year at the median in measured homes (ADEME), roughly 0.73 kWh a day: about $49 a year at the US average price or £71 under the UK price cap.
EnergyHow much does it cost to run a space heater?
A 1,500 W space heater costs about 27¢ per hour at full power at the US average electricity price, and a 2 kW heater about 53p per hour under the UK price cap. Calculator and examples.
EnergyHow much does it cost to boil a kettle?
Boiling 1 liter of water takes about 0.1 kWh: roughly 3p under the UK price cap, 2¢ at the US average price. The physics, a full-kettle example and how to cut the cost.
DIYHow many bags of concrete do I need?
One cubic yard of concrete takes 45 bags of 80 lb or 60 bags of 60 lb QUIKRETE Concrete Mix. Formulas, a bag chart for common slabs and post holes, and when to order ready-mix.
DIYHow much paint do I need for a room?
A 12 × 12 ft bedroom with 8 ft ceilings needs about 2.2 gallons for two coats on the walls. Step-by-step method, a chart by room size and the mistakes to avoid.
EnergyHow much electricity does a router use?
An internet router/box used 76 kWh a year at the median in measured homes (ADEME), an average of about 9 W: roughly $14 a year at the US average price or £20 under the UK price cap.
EnergyWatts vs kilowatt-hours: what's the difference?
Watts measure power (how fast energy is used); kilowatt-hours measure energy (how much is used over time). Clear examples, conversions and how to read your electricity bill.