kWp (Kilowatt Peak)
Unit for the maximum power output of a solar module or PV system under Standard Test Conditions (STC).
Also known as: Kilowatt Peak, kWpeak
What Does kWp Mean?
kWp (Kilowatt Peak) is the unit for the peak electrical power of solar modules and photovoltaic systems. The value indicates the maximum power achieved under standardised test conditions (STC): 1,000 W/m² irradiance, 25 °C cell temperature, and AM 1.5 spectrum.
Practical Significance
The kWp rating enables objective comparison of different solar modules and systems, regardless of manufacturer or technology. A typical residential rooftop system in Germany ranges between 5 and 15 kWp. Per kWp of installed capacity, an annual yield of approximately 900 to 1,100 kWh can be expected in Germany, depending on location, orientation, and tilt.
Relationship with Other Quantities
| Quantity | Meaning |
|---|---|
| 1 kWp | 1,000 Wp |
| Area per kWp | approx. 5—6 m² (modern modules) |
| Annual yield per kWp | approx. 900—1,100 kWh in Germany |
| Cost per kWp (2024) | approx. EUR 1,200—1,800 (installed) |
Practical Tip
The kWp rating describes performance under laboratory conditions. In real operation, actual power is usually lower due to temperature, shading, and module ageing. For yield planning, the site-specific yield in kWh per kWp should always be used.
Related Terms
Wp (Watt Peak)
Unit for the peak power of a single solar module under Standard Test Conditions (STC).
STC (Standard Test Conditions)
Standardised test conditions (1,000 W/m², 25 °C, AM 1.5) under which the rated power of solar modules is measured.
Solar Module
Assembly of multiple solar cells in a weatherproof housing for generating electricity from sunlight.
kWh (Kilowatt-Hour)
Unit of electrical energy -- one kWh equals the energy converted at a power of 1 kW over one hour.