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kWh Calculator

A kilowatt-hour (kWh) is the fundamental international billing unit of electrical energy, representing the consumption of 1,000 watts of power continu

Electrical
Power rating of electrical equipment
Select whether power is in Watts or Kilowatts
hours
Time duration the equipment operates
$/kWh
Rate used to calculate energy financial cost
Formula & Methodology
Energy (kWh) = Power (kW) × Time (hours) = [Power (Watts) ÷ 1000] × Time (hours)

To calculate kilowatt-hours, first convert power into kilowatts by dividing watts by 1,000 (if not already given in kW). Next, multiply the kilowatt rating by the number of hours the device operates. For example, a 2 kW appliance operating for 3 hours consumes exactly 2 × 3 = 6 kWh. To find financial cost, multiply the resulting kWh by your tariff rate.

Total Electrical Energy Consumed

6.00 kWh Kilowatt-Hours

Overview

A kilowatt-hour (kWh) is the fundamental international billing unit of electrical energy, representing the consumption of 1,000 watts of power continuously for exactly one hour. It is vital to understand that kW ≠ kWh: a kilowatt (kW) measures instantaneous power demand, while a kilowatt-hour (kWh) measures the total volume of electrical work performed over a duration of time.

This kWh Calculator converts any combination of electrical power (Watts or Kilowatts) and operating time (hours) into exact energy metrics across Watt-hours (Wh), Kilowatt-hours (kWh), and Megawatt-hours (MWh). Use this tool to calculate solar battery bank capacities, audit commercial power draw, or verify appliance energy claims.

Worked Examples

2 kW Appliance Run for 3 Hours at $0.16/kWh

Power = 2 kW (or 2,000 W), Duration = 3 hours, Rate = $0.16/kWh.

  1. Identify Power in Kilowatts: 2.0 kW
  2. Multiply by Time in Hours: 2.0 kW × 3 hours = 6.0 kWh
  3. Convert to Watt-Hours: 6.0 kWh × 1,000 = 6,000 Wh
  4. Calculate Financial Cost: 6.0 kWh × $0.16 = $0.96
Final Answer: 6.00 kWh (6,000 Wh | Financial Cost: $0.96)

500-Watt Sump Pump Running for 18 Hours

Power = 500 W, Duration = 18 hours, Rate = $0.15/kWh.

  1. Convert Watts to kW: 500 W ÷ 1,000 = 0.5 kW
  2. Calculate Energy: 0.5 kW × 18 hours = 9.0 kWh
  3. Cost: 9.0 kWh × $0.15 = $1.35
Final Answer: 9.00 kWh ($1.35)

Large 10 kW Commercial Bakery Oven Run for 8 Hours

Power = 10 kW, Duration = 8 hours, Rate = $0.12/kWh.

  1. Energy: 10 kW × 8 hours = 80.0 kWh (0.08 MWh)
  2. Cost: 80.0 kWh × $0.12 = $9.60
Final Answer: 80.00 kWh ($9.60)

How to Use This Calculator

  1. Enter the electrical power draw of your equipment.
  2. Select whether the power is specified in Watts (W) or Kilowatts (kW).
  3. Enter the operating duration in hours.
  4. Enter your local electricity rate per kWh to calculate monetary cost.
  5. Click Calculate to see total energy consumed in kWh, Wh, and MWh.

Reference Table

Energy UnitEquivalent in Watts / TimeEquivalent in kWhTypical Application
1 Watt-Hour (Wh)1 Watt for 1 hour0.001 kWhSmall electronics, cell phone battery capacities
1 Kilowatt-Hour (kWh)1,000 Watts for 1 hour1.0 kWhResidential electricity metering, appliance ratings
1 Megawatt-Hour (MWh)1,000,000 Watts for 1 hour1,000 kWhIndustrial factories, EV fleet charging depots
1 Gigawatt-Hour (GWh)1 Billion Watts for 1 hour1,000,000 kWhMunicipal power grid and utility power plant outputs

Frequently Asked Questions

What is the formula to convert Watts to kWh?
The formula is: kWh = (Watts × Hours) ÷ 1,000. For example, a 100-watt light bulb turned on for 10 hours uses (100 × 10) ÷ 1,000 = 1.0 kWh.
How much is 1 kWh of electricity in real terms?
One kilowatt-hour provides enough energy to run a 10-watt LED bulb for 100 hours, power a desktop computer for 4 to 5 hours, watch television for 10 hours, or drive an electric car for approximately 3 to 4 miles.
Is kWh a measure of power or energy?
kWh is strictly a measure of energy (work performed). Power is the rate of energy transfer, measured in Watts or Kilowatts. Running a 1 kW generator for 1 hour generates 1 kWh of energy.
How do solar battery systems use kWh ratings?
Home energy storage systems (like a Tesla Powerwall or Enphase battery) are rated in usable kWh capacity (e.g., 13.5 kWh), indicating how much total electrical energy they can deliver before requiring a recharge.
Can I convert kWh back into Watts?
To convert kWh back to Watts, you must know the duration of time: Watts = (kWh × 1,000) ÷ Hours. Without knowing operating time, you cannot convert energy back into power.

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Reviewed & Authored by: OnlineConvers Engineering Editorial Team · Last Updated: 2026-10-07
Kilowatt-hour computations apply the exact definition of electric energy E = P × t, converting watts to kilowatts via division by 1,000. Energy metrics across Wh, kWh, and MWh are computed at full floating-point precision and formatted deterministically. Tariff multiplication evaluates linear volumetric costs.
Citations: Units of Energy and Power: Bureau International des Poids et Mesures (BIPM) (International System of Units (SI)) · Electrical Energy Measurements and Kilowatt-Hour Standards (National Institute of Standards and Technology (NIST))