kW to kWh

Turn a power rating and a running time into the energy consumed — and what it costs at your tariff.

Need the power figure before the energy figure? Work it out with the kVA to kW converter first.

kW to kWh Calculator

kWh = kW × hours
5 kW
kW
8 h
h
Quick values
0.15 per kWh
per kWh

In your own currency

At a glance

kWh = kW × hours
Energy used
40 kWh
Power
5 kW
Running time
8 h
Electricity rate
0.15 per kWh

Every diagram and table on this page updates with the calculator above.

Output

Live
Energy used
40kWh
kWh = 5 kW × 8 h = 40 kWh
Running cost6
If run 24 h120 kWh

The kW to kWh Formula

The conversion everyone needs and almost everyone states incorrectly at least once.

kWh = kW × hours

A kilowatt is a rate; a kilowatt-hour is the energy that rate delivers in an hour.

Kilowatt (kW)
Power — how fast energy is flowing right now. It is an instantaneous quantity.
Kilowatt-hour (kWh)
Energy — an amount that has accumulated. This is what your meter counts and your bill charges.
Load factor
Average power ÷ peak power over a period. Low load factors mean expensive demand charges.
There is no such thing as "kW per hour"

The phrase mixes a rate with a duration. A 5 kW load running for 8 hours uses 40 kWh — never "40 kW per hour".

The conversion

Live
Input5kW
Result40kWh
Power multiplied by time

Energy Accumulates While the Load Runs

The shaded area is the energy consumed: constant height for a steady load, growing wider with every hour it runs. Both dimensions matter equally — halving the power or halving the time saves exactly the same energy.

Real loads are rarely rectangles. Thermostatically controlled equipment cycles on and off, so its average power is well below its rating — which is why a 2 kW fridge compressor does not use 48 kWh a day.

Energy over time

Live
5 kW024 h
Energy delivered40 kWh
Area = power × time

What It Actually Costs to Run

Cost = kW × hours × rate

Enter your own tariff in the calculator to get a figure in your currency.

An always-on 300 W server

Given
  • Power: 0.3 kW
  • Running: 24 h/day, 365 days
  • Tariff: 0.15 per kWh
Working
  1. Annual kWh = 0.3 × 8,760 = 2,628
  2. Cost = 2,628 × 0.15

About 394 per year — and roughly the same again to remove the heat if it sits in a cooled room.

Tariff elementCharged onTypical unit
Energy chargeEvery kWh consumedper kWh
Standing chargeEvery day, regardless of useper day
Maximum demandHighest kW in the periodper kW per month
Power factor penaltyReactive power or low PFper kVArh or a surcharge
Time-of-use bandkWh in peak hourshigher per kWh

Cost against run time

Live
55800744Running time (h)
8 h6 cost
Cost accumulating across the whole time range at your tariff

Energy Use by Running Time

How your power rating accumulates over different durations, with the cost at your tariff.

Conversion chart

Live
hEnergy (kWh)Cost ()
0.5 h2.50.38
1 h50.75
2 h101.5
4 h203
6 h304.5
8 h406
10 h507.5
12 h609
16 h8012
24 h12018
48 h24036
168 h840126
730 h3,650547.5

Energy for Every Load and Duration

Read down for bigger loads, across for longer runs. The highlighted cell tracks the calculator.

kWh lookup grid

Live
kWh for each kW × h combination
kW1 h4 h8 h24 h168 h
0.5 kW0.5241284
1 kW14824168
2 kW281648336
5 kW52040120840
10 kW1040802401,680
25 kW251002006004,200
50 kW502004001,2008,400

What Ordinary Things Consume

AppliancePowerTypical daily kWh
LED lighting, whole house60 W0.3
Fridge-freezer150 W cycling1.0 – 1.5
Desktop computer150 W1.2
Electric shower8.5 kW1.4 (10 min)
Tumble dryer2.5 kW2.5 (1 cycle)
Electric vehicle charging7 kW20 – 40
Air-source heat pump2 – 4 kW10 – 30 in winter

Notice how the big numbers come from things that run long hours, not from the highest-rated appliances. A 60 W lamp left on all day beats a 2 kW kettle used twice.

Consumption bands

Live
Single appliance
Household day
Large home
Commercial
40 kWh
Where your figure sits against familiar consumption levels

Three Levers That Actually Cut the Bill

  1. Reduce the power

    More efficient equipment lowers the height of the rectangle. Best where a load runs constantly.

  2. Reduce the hours

    Controls, timers and occupancy sensors narrow the rectangle. Usually the cheapest intervention by far.

  3. Move the hours

    Shifting consumption to an off-peak band does not save energy, but it cuts cost on a time-of-use tariff.

Quick audit
  • Identify the three largest continuous loads — they dominate the bill.
  • Check whether anything runs outside occupied hours without needing to.
  • Compare your peak kW against the demand charge on the tariff.
  • Look for equipment left idling rather than switched off.
  • Verify that timers and setpoints still match how the site is actually used.

Three schedules

Live
8 h/day
Energy
40 kWh
Cost
6
12 h/day
Energy
60 kWh
Cost
9
24 h/day
Energy
120 kWh
Cost
18
The same load on three different operating schedules

Every Power Converter in One Place

29 calculators built on the same maths as the tool above. Each one has its own inputs, interactive diagrams and worked examples.

View all converters

kW to kWh Questions

Common questions about converting kw to kwh.

Multiply power by the hours it runs: kWh = kW × hours.

120 kWh if it runs continuously for 24 hours. Most equipment runs intermittently, so multiply by the actual running hours instead.

No. kW is the rate of energy use at any instant; kWh is the total energy consumed over time.

Multiply its kilowatt rating by the hours used, then by your tariff per kWh. Remember that thermostatically controlled appliances cycle on and off.

A commercial tariff component based on the highest kW recorded in a billing period, charged separately from the kWh consumed.

Standing charges, time-of-use bands, demand charges and taxes sit on top of the energy cost. The kWh figure is only one line of the bill.

A little. Standby consumption is typically 0.5–3 W per device, which adds up across a house but is small next to heating and hot water.

Related Converters

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