kW to kWh Calculator

kW measures power, the rate of consumption at an instant; kWh measures energy, the amount consumed over time. The relationship is the same as speed and distance: speed tells you how fast you are going, distance tells you how far you went. A 10 kW machine running for 8 hours uses 80 kWh. Suppliers bill you for the kWh consumed, while supply capacity and demand charges relate to kW or kVA.

Multiply power by time: kWh = kW x hours. A 3 kW heater on for 5 hours uses 15 kWh; a 50 kW chiller running continuously uses 1,200 kWh per day. For loads that cycle on and off, use the actual running hours, not the hours the equipment is switched on: a compressor at 50 percent duty over a 10 hour shift counts as 5 running hours.

Yes. The unit on a UK electricity bill is one kilowatt-hour, so a tariff quoted in pence per unit is pence per kWh, and the consumption line on your invoice is simply the kWh recorded by your meter between reads. Once this calculator gives you kWh, multiply by your own contract unit rate to estimate cost; rates vary by contract, so use the figure on your agreement.

Double it. Each half-hourly reading is the energy used in 30 minutes, so the average power across that period is the kWh figure multiplied by two. A reading of 45 kWh in a settlement period means an average demand of 90 kW. Your maximum demand, which matters for capacity charges and DCP161 excess charges, is the highest of these half-hourly averages, expressed in kW or kVA.

No, it uses 1 kWh: 2 kW x 0.5 hours. Mixing up the rating and the consumption is the most common error in load estimates. The kW figure on a rating plate is also a maximum, not a typical draw; many machines spend much of their time below it, so metered kWh often comes in lower than a plate-based estimate. Sub-metering gives the true figure where the load justifies it.