kW to kWh Calculator - Power Used Over Time

Agarapu Ramesh — Editor and content reviewer
Editorially reviewed Reviewed by Agarapu Ramesh, science educator (chemistry). LinkedIn
Last reviewed: May 2026 | Standard electrical engineering formulas

kW is how fast energy is being used. kWh is how much energy was used over time. A 2 kW load running for 3 hours uses 6 kWh. Same power, longer time, bigger bill.

Formula at a glance

  • kWh = kW x hours
  • hours = kWh / kW
  • cost = kWh x rate

Field note: A device rated 1 kW does not use 1 kWh until it runs for one hour. This is the unit mix-up that never seems to die.

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kW to kWh Calculator

Convert power to energy

kW
hrs
Result
—

Formula

kWhE = P × t

Where:
E = Energy (kWh)
P = Power (kW)
t = Time (hours)

Quick Reference

kW 1 hour 8 hours
1 kW 1 kWh 8 kWh
2 kW 2 kWh 16 kWh
5 kW 5 kWh 40 kWh

Related

kWh to kWWatts to kWhElectricity Bill

How to use the kW to kWh Calculator

Use this as a unit check for energy, power and time. Keep the time period honest, because a one-hour run and a one-month run can make the same load look completely different.

Worked example

Example: a 1.5 kW heater running 4 hours uses 6 kWh. At $0.18 per kWh, that run costs $1.08.

Practical checks before you trust the number

  • Use average kW for cycling loads like AC or refrigeration.
  • For battery planning, remember inverter losses.
  • For utility bills, use the total kWh on the meter, not peak kW.

Common mistake

A device rated 1 kW does not use 1 kWh until it runs for one hour. This is the unit mix-up that never seems to die.

Sources and references

Related calculators

Frequently Asked Questions

kWh = kW × hours. Example: a 2 kW heater running 3 hours uses 6 kWh. This is the formula behind every electricity bill. Multiply by the tariff rate (I/kWh) to get cost. We teach this on day one because it's the most-used formula in residential energy auditing.

kWh = kW × hours. That's it. No PF, no √3 — kWh is just energy = power × time. Example: 1.5 kW AC running 8 hours → 12 kWh. For per-month estimates, multiply by 30 days. For per-year, multiply by 365. Simple, but powerful for cost projection.

kWh = kW × hours = 2 × 5 = 10 kWh. At a tariff of I6/kWh, that's I60 per use. Run it daily and the monthly cost is I60 × 30 = I1800. This kind of quick math helps customers understand which appliance is driving their bill.

kW is power — the rate of energy use at any instant. kWh is energy — the total amount used over time. Think of kW as speed and kWh as distance. A 2 kW appliance running for 3 hours uses 6 kWh, just like a car at 60 km/h for 3 hours covers 180 km. Confusing the two is the most common rookie error in energy audits.

Monthly kWh = kW × hours per day × 30. Example: 1 kW running 8 hours per day → 1 × 8 × 30 = 240 kWh per month. For mixed loads, sum each appliance's contribution. This gives a realistic forecast you can compare against the actual electricity bill to find inefficiencies.

No. kWh requires time. kW × time = kWh. Without time, you only know the rate of energy use, not the total energy. So a 2 kW load tells you how fast energy flows, but you must know the runtime to compute the kWh consumed. Always ask for usage hours when estimating cost.

Yes, that's its main job. Enter appliance kW and daily/monthly hours, multiply, and you get the energy consumption in kWh. Multiply by tariff for cost. Example: AC 1.5 kW × 6 h/day × 30 = 270 kWh/month. At I7/kWh, that's I1890/month for one AC. This kind of clarity drives smart appliance choices.