Capacity / power / nominal power

kWh / kW / kWp

In the jungle of abbreviations and technical terms we explain the meaning and differences of terms. Our first part deals with kWh / kW / kWp, i.e. capacity, input and output power and nominal power of photovoltaics.

kWh = capacity

Battery storage systems are measured in kWh (kilowatt hours). The total capacity of the battery storage is indicated in kWh, which is the total volume of stored energy.

Imagine a water tank. In our comparison, the capacity of the tank corresponds to the capacity of a battery storage. GREENROCK Home storage systems are available from a capacity of 5 kWh to 30 kWh and GREENROCK Business storage is available from 30 kWh to 270 kWh.

Stacksaltwater battery with 2,5 kWh

kW = power

The power is specified in W (Watt) or kW (kilowatt = 1,000W). To stay with the above example of the water tank, the power is shown with a hose for inlet or outlet. The thicker the hose, the more power you can draw from the tank. At high power the tank will empty faster. Our GREENROCK storage systems provide constant performance over 5 hours. They are designed to ensure long-term supply during the night hours. The capacity of your electrical appliances is also indicated in kW. For example, a dough mixer has a power of 1,000 W. If you operate it for a full hour, you have consumed one kWh.


kWp = nominal power of the PV

kWp (kilowatt peak) specifies the maximum output of the photovoltaic system. This means that under optimal conditions (position of the sun, no clouds, …) the PV system can produce the specified output. The actual energy (effective power) is then measured in kW. In most cases, the active power is slightly lower than the specified nominal power in kWp. If you want to dimension the size of a battery storage, you take into account the kWp output of the PV system and self-consumption. How much electricity can I produce? How much electricity is consumed directly (immediately)? How much is left over and should be stored for the night hours?

PV Paneele