kWh (Kilowatt-Hour)
Unit of electrical energy -- one kWh equals the energy converted at a power of 1 kW over one hour.
Also known as: Kilowatt-Hour
What Is a kWh?
The kilowatt-hour (kWh) is the most common unit of electrical energy. One kWh equals the amount of energy generated or consumed at a constant power of one kilowatt (1,000 watts) over one hour.
Significance for Photovoltaics
In the solar industry, the kWh is used to measure both generated solar electricity and household consumption. An average four-person household in Germany consumes about 4,000 to 5,000 kWh per year. A PV system with 10 kWp generates approximately 9,000 to 11,000 kWh annually in Germany.
Examples
| Device / System | Energy Amount |
|---|---|
| Washing machine (one cycle) | approx. 1 kWh |
| Refrigerator (per day) | approx. 0.5—1 kWh |
| 10 kWp PV system (per year) | approx. 9,500 kWh |
| Feed-in tariff (per kWh) | 8.1 ct (2024, surplus feed-in) |
Practical Tip
For the economic evaluation of a solar system, the comparison between the levelised cost of electricity (in cents per kWh) and the current grid electricity price is decisive. Self-generated solar electricity costs about 5—10 cents per kWh today, which is significantly cheaper than grid electricity.
Related Terms
kWp (Kilowatt Peak)
Unit for the maximum power output of a solar module or PV system under Standard Test Conditions (STC).
Self-Consumption
Share of self-generated solar electricity consumed directly in the household rather than fed into the grid.
Feed-in Tariff
Legally guaranteed remuneration for solar electricity fed into the public grid, governed by the EEG.
Levelised Cost of Electricity (LCOE)
Total cost of electricity generation per kWh over the lifetime of a system -- for PV currently 5--10 cents/kWh.