Photovoltaic (PV) system sizes are listed in a variety of kilowatt (kW) terms:
- Nameplate kW (or Standard Test Conditions, STC)
- PVUSA Test Conditions kW (PTC)
- CEC-AC kW , after the inverter efficiency is applied
- CSI-kW, which includes site-specific design conditions that may reduce annual generation
Example: On the SF Peninsula a 1 kilowatt (AC) PV system is estimated to generate between 1,600 and 1,800 kilowatt-hours (kWh) per year. Therefore to calculate the system size needed to meet all your electric consumption, divide your annual electric consumption (kWh) by 1,700 to get a the PV system size in kilowatts (CEC-AC).
Your results may vary!