kWp

Kilowatt-peak (kWp) is the power a set of panels is rated to produce in standard laboratory test conditions. It describes the panels’ size, not what they’ll produce on your balcony. A kit with two 440 Wp panels is 0.88 kWp.

For plug-in solar, keep kWp separate from the 800 W limit. The legal cap applies to the inverter’s AC output, while the panels can add up to 2,000 W (2 kWp) of DC power (IPS §4.1). If the panels could produce more than 800 W at a given moment, the inverter clips the extra. The specification also says that above 960 W of panels, manufacturers must advise you to consider a professional check of your electrical installation.

Yield figures are often quoted in kWh per kWp, which is how PVGIS, the EU tool we use, works (PVGIS). Multiply by the kit’s kWp for a rough annual total, but remember that clipping at 800 W reduces it for larger arrays.