kWh: power vs energy
The unit you trade. Easy to mix up. Worth getting right on day one.
The market sells energy, not power. Two words. Two different things.
- Power is a rate. The kettle is using 9 kW right now. Think of it as the speedometer.
- Energy is an amount. The kettle used 0.9 kWh in the last 6 minutes. Think of it as the odometer.
You get energy by multiplying power by time.
flowchart LR
P([Power<br/>9 kW]) --> T([× Time<br/>6 minutes])
T --> E([= Energy<br/>0.9 kWh])
style P fill:#dbeafe,stroke:#1e40af,color:#1e3a8a
style T fill:#fef3c7,stroke:#a16207,color:#713f12
style E fill:#fed7aa,stroke:#c2410c,color:#7c2d12
Same formula at the big scale. A 2 MW wind turbine running flat out for one hour gives 2 MWh. At a Nord Pool price of 600 SEK/MWh, that hour is worth 1,200 SEK.
Where each unit shows up
| You see this | It is talking about |
|---|---|
| MW on a turbine, a generator, a battery | power (rate) |
| MWh on a market price, a bill, yearly output | energy (amount) |
| kW on a heat pump or a charger | power (rate) |
| kWh on your monthly bill | energy (amount) |
Quick test. My house used 6 kW yesterday. What is wrong with that sentence? 6 kW is a rate, not an amount. They probably meant 6 kWh.
Next
Now the strange rule that shapes the rest of the market. See The one weird rule.