KWp is the nameplate rating of Solar PV modules and kW is the actual power delivered to the load. For instance, a 0.3kWp (300Wp nameplate) module under ideal conditions (25 degrees C and 1000 watts per sq. metre radiation, etc.) will give an output of 0.3kW. However, in real life weather conditions, the output will be lower than the nameplate rating which is denoted in kW.