About this tool
Solar Inverter Sizing & DC-AC Ratio Calculator is a free, in-browser tool that recommends the inverter AC rating for a PV array and checks the DC-to-AC ratio (the inverter load ratio, or ILR) for clipping. It reports the recommended AC size in watts and kW, your current ratio, and whether it sits in the healthy band.
The recommended AC size is arrayDC ÷ targetRatio, with a default target of 1.2 — arrays are deliberately oversized relative to the inverter because panels rarely hit nameplate output. If you enter an inverter AC rating, the ratio is arrayDC ÷ inverterAC; below 1.15 the inverter is oversized (wasted cost), above 1.5 the array is so large the inverter clips peak production, and 1.15–1.5 is the normal design band.
Use it to pick a string or hybrid inverter for a given array, or to check whether an existing inverter is well matched. Enter the array DC watts, choose a target ratio, and optionally your inverter's AC rating to see the clipping assessment. All computed in your browser.
Frequently asked questions
What is the DC-AC ratio (ILR)?
It is the array's DC nameplate watts divided by the inverter's AC watts. Because modules seldom produce full nameplate power, a ratio above 1 lets a smaller, cheaper inverter run near capacity more of the time without wasting energy.
Is a ratio above 1 a mistake?
No — oversizing the array is standard practice. A ratio of about 1.1–1.3 is typical and 1.5 is a common upper limit. Only past that do you clip enough peak output for the loss to outweigh the inverter savings.
What does clipping mean?
When the array briefly produces more DC power than the inverter's AC rating, the inverter caps output and the excess is lost. A little clipping at midday peaks is economically fine; heavy clipping means the inverter is undersized for the array.
What if I leave the inverter field blank?
The tool still gives you the recommended AC size from your array and target ratio; the ratio and clipping assessment simply wait until you enter an inverter rating to compare against. Everything runs locally in your browser.
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