To convert kW to kWh, multiply total electrical power by operating time: kWh = kW × hours. A constant 5 kW load running for 3 hours uses 15 kWh. The same relationship applies to single-phase and three-phase loads when the input is already total electrical kW.
kW → kWh Calculator
How to calculate kWh?
Why system phase matters?
kW to kWh conversion table
These values assume the stated total electrical input remains constant throughout the interval. One table covers all phase arrangements; the kW-to-kWh conversion does not need a phase multiplier.
| Power (kW) | 1 hour (kWh) | 4 hours (kWh) | 8 hours (kWh) | 24 hours (kWh) |
|---|---|---|---|---|
| 0.5 | 0.5 | 2 | 4 | 12 |
| 1 | 1 | 4 | 8 | 24 |
| 2 | 2 | 8 | 16 | 48 |
| 3 | 3 | 12 | 24 | 72 |
| 5 | 5 | 20 | 40 | 120 |
| 7.5 | 7.5 | 30 | 60 | 180 |
| 10 | 10 | 40 | 80 | 240 |
| 15 | 15 | 60 | 120 | 360 |
| 20 | 20 | 80 | 160 | 480 |
| 30 | 30 | 120 | 240 | 720 |
| 50 | 50 | 200 | 400 | 1200 |
| 60 | 60 | 240 | 480 | 1440 |
Formula: power multiplied by time
E (kWh) = P (kW) × t (hours). Convert minutes to hours by dividing by 60. If power changes, calculate each interval separately and add the energy: E = P₁t₁ + P₂t₂ + … .
The U.S. Energy Information Administration explains the distinction between power and energy: watts and kilowatts measure power, while watt-hours and kilowatt-hours measure energy over time.
Single-phase, split-phase and three-phase inputs
The calculator’s system selector is a reference label; it does not change the result. Enter the load’s total electrical input in kW. Do not multiply that value by 2, 3 or √3 simply because the supply has multiple conductors or phases.
Phase configuration matters when you first derive power from voltage and current. For a single-phase AC load, electrical kW = V × I × PF ÷ 1,000. For a balanced three-phase load, electrical kW = √3 × VLL × IL × PF ÷ 1,000, using line-to-line voltage and line current. Once that total kW is known, multiply it by hours once. For an unbalanced system, use measured total active power or sum the individual phase powers.
A residential 120/240 V split-phase service is single-phase. Its two hot conductors do not mean that an already-known total kW value should be doubled.
Power factor and motor efficiency are different
Do not multiply or divide an electrical kW input by PF again. PF connects apparent power and real power: electrical kW = kVA × PF. If your starting value is apparent power, use our kVA to kW calculator first.
Motor nameplate kW often denotes mechanical shaft output. If that is your starting value, electrical input kW = shaft output kW ÷ efficiency, with efficiency expressed as a decimal. Use efficiency and power at the actual operating load. If measured electrical input is already available, do not apply efficiency again.
Worked kW to kWh examples
| Scenario | Calculation | Energy |
|---|---|---|
| 3 kW heater, 4 hours actually heating | 3 × 4 | 12 kWh |
| 15 kW total electrical input, three-phase, 8 hours | 15 × 8 | 120 kWh |
| 20 kW electrical input, PF 0.85, 10 hours | 20 × 10; no second PF factor | 200 kWh |
| 15 kW shaft output, efficiency 90%, 8 hours | (15 ÷ 0.90) × 8 | 133.33 kWh |
| 7.2 kW electrical input, 45 minutes | 7.2 × (45 ÷ 60) | 5.4 kWh |
| 5 kW for 4 hours, 7 kW for 2 hours, 3 kW for 6 hours | (5 × 4) + (7 × 2) + (3 × 6) | 52 kWh |
A thermostat-controlled heater may be connected for 4 hours without heating for all 4 hours. Use measured average power, actual on-time, or an appropriate duty-cycle estimate. Standby consumption should be added separately when relevant.
From kWh to electricity cost
Energy charge = kWh × price per kWh. For an illustrative flat rate of $0.20/kWh, a 5 kW load operating 4 hours daily for 30 days uses 600 kWh and costs $120 in energy charges. Use the rate on your bill; fixed charges, demand charges, taxes and tiered or time-of-use pricing may require separate calculations.
For several appliances, open the electricity cost calculator with an appliance inventory. Enter quantities, watts, hours, duty cycles, days and your rate; save alternative scenarios and download the inventory. If your equipment label is in watts, the watts to kWh calculator handles the division by 1,000.
Compare power, energy and operating schedules in our kW vs kWh guide with worked examples.
Frequently asked questions
How many kWh is 1 kW?
It depends on time: a constant 1 kW load uses 1 kWh in one hour, 8 kWh in eight hours and 24 kWh in 24 hours.
Does a three-phase 10 kW load use 30 kWh in one hour?
No. If 10 kW is the total electrical input, it uses 10 kWh in one hour. Multiplying total power by three would count the phases again.
Can I convert kWh back to kW?
Average kW = kWh ÷ hours, for a nonzero duration. For example, 60 kWh over 12 hours corresponds to 5 kW average power. It does not reveal the highest instantaneous power.
Does improving power factor automatically reduce kWh?
No. For the same measured active power and operating time, kWh stays the same. Power-factor correction can affect current, system losses or tariff charges, but those effects require their own assessment.