Power StationsWORLDWIDETHE GLOBAL EDITION 01
Electricity essentials

MW vs MWh: reading power and energy correctly

Understand megawatts, megawatt-hours, plant capacity, average output and the limits of converting station size into annual electricity.

By Power Stations Worldwide · Reviewed 28 September 2026 · Editorial approach

What is the difference between MW and MWh?

MW measures power: the rate of producing or using energy. MWh measures an amount of energy over time. A station’s MW figure describes its rated size; an MWh figure needs a reporting period. Keeping that distinction prevents the most common error when reading a power-plant map.

Sources: EIA: Measuring electricity

How do I convert MW into MWh?

Multiply average power in MW by elapsed hours. In an illustrative calculation, a generator maintaining 20 MW for three hours delivers 60 MWh. If its output changes, calculate each interval separately and add the energy. A single peak output reading cannot establish a whole day’s production.

Sources: EIA: Measuring electricity

How do kW, MW, GW and TWh relate?

Each step from kW to MW to GW multiplies power by 1,000. For energy, 1 GWh equals 1,000 MWh, and 1 TWh equals one million MWh. Convert both compared values to the same unit before calculating a ratio; retain the hour when expressing energy.

Sources: EIA: Measuring electricity

Does a 100 MW power station always produce 100 MW?

No. Capacity is a rating, while actual generation changes with operating conditions and scheduling. Maintenance, fuel or resource availability, and the demand for electricity can affect output. Treat a 100 MW record as information about rated capability, not evidence of what the station is producing now.

Sources: EIA: Generation, capacity and sales

How can I estimate annual generation from capacity?

You also need a justified capacity factor and the hours in the period. The relationship is energy = capacity × hours × capacity factor. For illustration, 10 MW × 8,760 hours × 0.50 is 43,800 MWh. That assumed factor is an example, not a forecast for a real plant.

Sources: EIA: Capacity definitions

What is the difference between gross and net generation?

Gross generation is measured before subtracting electricity used to operate the generating plant. Net generation deducts those station requirements. Compare figures measured on the same basis; a gross number and a net number can differ even when both correctly describe the same facility and reporting period.

Sources: EIA glossary: Net generation and capacity

Can I convert a station’s MW rating into homes supplied?

Not reliably from capacity alone. You would need actual or explicitly assumed generation and a household-consumption benchmark for the same period and place. Peak demand adds another question. This atlas therefore displays reported capacity instead of presenting a universal homes-powered conversion as a plant fact.

Atlas context: Data coverage and methodology

Which units should I use when exploring this atlas?

Use MW to compare reported station size and TWh to compare country electricity production. Record the year beside either quantity. When moving from a map record to Energy Insights, remember that a plant inventory and an annual national energy balance answer different questions and may use different source dates.

Atlas context: Data coverage and methodology

Textbook references

The science on this page follows these standard engineering textbooks. See the full bibliography.

  1. Renewable and Efficient Electric Power Systems (2nd ed.) — Masters, G. M., Wiley-IEEE Press, 2013 · ISBN 978-1-118-14062-8Power, energy and electrical units.
  2. Sustainable Energy — Without the Hot Air — MacKay, D. J. C., UIT Cambridge, 2009 · ISBN 978-0-9544529-3-3 · free to readConverting between power and energy in everyday terms.

Keep exploring