What is the difference between a megawatt and a megawatt-hour?
A megawatt measures how fast electricity flows at one moment. A megawatt-hour measures how much was delivered over time.
Think of a tap and a bucket. The megawatt, MW, is the size of the tap: the rate at which power can flow. The megawatt-hour, MWh, is the water in the bucket: the energy actually delivered. A 100 MW plant running flat out for one hour produces 100 MWh.
The distinction matters most for batteries. A battery described as 100 MW and 400 MWh can deliver 100 MW for four hours. One described as 100 MW and 100 MWh empties in one hour. Both have the same headline power and very different uses and prices.
It also explains why capacity figures for solar and wind need care. A 100 MW solar farm only reaches 100 MW around midday in good weather. Over a year it delivers perhaps a fifth to a quarter of what a plant running continuously at 100 MW would.
- MW
- Power. A rate
- MWh
- Energy. A quantity
Explainers describe how things generally work. They are not advice for a specific project or country. See our editorial policy.