What is the difference between system power output and system energy production?
The AC power output of a solar array, measured in watts (W) or kilowatts (kW), is typically given on inverter output displays or remote monitoring sites. It is an instantaneous measurement, determined by the rated DC power output of the solar array, inverter efficiency and system losses, and is proportional to solar irradiance on the array.
The AC energy production of a solar array, measured in kilowatt-hours (kWh), is measured over periods of months and years to compare with sizing and long-term performance expectations. Solar kWh energy production is also typically given on inverter output displays or remote monitoring sites and can be compared with a household.
Note that for grid-connected PV systems, power generated by the solar PV system will first offset any electrical loads in the house, reducing the amount of kilowatt-hours purchased from the utility.