How to Use the Solar Inverter Size Calculator
It's tempting to assume your inverter should match your panel capacity exactly, but in practice, inverters are usually sized a bit smaller than the panel array. Enter your total panel capacity and a DC:AC design ratio, and this calculator instantly returns the recommended inverter size.
The DC:AC ratio is your panels' total DC capacity divided by the inverter's rated AC capacity. Panels only approach their full rated output briefly around solar noon on a clear day, and produce less than that most of the time — so sizing the inverter 1.1-1.3x smaller than the array barely reduces total energy captured while cutting the cost of the inverter itself.
For example, a 5kW panel array designed at a 1.2 ratio needs roughly a 4.17kW inverter. A lower ratio (1.1) gives more headroom but costs more; a higher ratio (1.3) saves money but can increase "clipping" losses — power lost when output briefly exceeds the inverter's rated capacity on sunny midday hours. Around 1.2 is a common middle-ground choice for residential systems.
Frequently Asked Questions
It's the ratio of your panels' total DC capacity to the inverter's rated AC capacity. Designing between 1.1 and 1.3 typically lets you use the inverter more efficiently.
No. Panels rarely produce their full rated output, so it's common practice to size the inverter slightly smaller than the panel array (1.1-1.3x lower).