As we know, the solar panels will produce DC electricity which will be converted to AC electricity afterwards via solar inverter. The AC electricity will be injected to the power grid or to be used directly to power our loads like domestic or commercial building or any other applications.
What we are searching for here is what should be the ratio between DC power generated from the solar panel and inverter AC power (its power rating), what are the advantages and disadvantages if this ratio is above 1 (means solar panel DC generated power is larger than inverter power rating)?
How does the solar inverter output AC power change throughout the day?
Usually at the beginning of the day, the AC output power of solar inverter is low, then it increases gradually with the increasing of the sun light reaching its max at noon time (2-3pm), then it reduces gradually and reaches its lowest value at the end of the day with the sun light absence. So, it’s like a bell curve.
So normally, oversizing the solar array power capacity will shift this curve up, which means more energy production can be gotten and vice versa.
Solar inverter clipping
When DC power generated from the solar panels is larger than the inverter power rating, and this is happening when we oversize the solar panels power capacity (ratio is above 1) and during noon time (peak production hours) where the solar irradiance is at or above standard test condition value (1000 W/m2 ), at that point the extra DC power generated above inverter rated capacity will be clipped by the inverter to ensure its working at its rated value, and resulting in some of energy production lost, and this is the only disadvantage of oversizing the solar panels over the inverter capacity (above one ratio).
In the other side, oversizing the solar panels power capacity will increase energy production in most of day times especially at the morning and at the end of the day (late afternoon).
So, the solar system designer should take into consideration the energy production loss due to solar inverter clipping and the increase of energy production due to oversizing the solar array (in the morning and late afternoon times), as aforementioned. of course, depth analysis and simulation should be done to indicate to what extent we should oversize the solar array above the inverter capacity.
Some solar systems designers add another solar inverter to increase energy production while avoid solar inverter clipping, but the second solar inverter price and installation cost should be taken into consideration in compare to extra energy yield we shall get.