Most installations slightly oversize the inverter, with a ratio between 1.1-1.25 times the array capacity, to account for these considerations. The size of the solar inverter you need is directly related to the output of your solar panel array. The inverter’s capacity should ideally match the DC rating of your solar panels in kilowatts (kW).
An important consideration in calculating inverter size is the solar panel system:inverter ratio. This is the direct current capacity of the solar array divided by the maximum alternating current output of the inverter. For example, a 3kW solar panel system with a 3kW inverter has an array-to-inverter ratio of 1.0.
Correct sizing of a solar inverter is crucial. The wrong inverter capacity will weaken the performance of the solar panel system. The inverter has to be able to deal with the amount of energy it’s getting from the panels. Inverter sizes are measured in watts (W) or kilowatts (kW) – units of a thousand watts – the same as solar panels.
Commercial solar systems will require higher capacity inverters. Inverters work most efficiently at their maximum power and as a general rule should roughly match the solar panel output. For instance, a 3kW solar panel system needs a power inverter of 3kW or thereabouts. The capacity ratings don’t necessarily have to match exactly.
Apart from solar panel system size, roof size, location and temperature, other factors that can influence the size of inverter you’ll need include: The angle of your solar panels, and their orientation relative to the sun. Shade from neighbouring buildings or nearby trees. The amount of dust or pollution in the air.
For instance, a 3kW solar panel system needs a power inverter of 3kW or thereabouts. The capacity ratings don’t necessarily have to match exactly. Inverters can be sized lower than the kilowatt peak (kWp) of the solar array. This is because solar panels rarely achieve peak power.