Working backward from a fixed inverter
Why start from the inverter instead of the array
Most sizing tools start with a target system size and work toward an inverter that fits it. This one flips that order, useful when the inverter choice is already locked in, whether from a specific product preference, a bulk equipment purchase, or a design constraint elsewhere in the project. Every clipped kilowatt-hour still has a value, which the cost per kWh produced calculator can put a price on. Given that fixed AC rating, the real question becomes how much DC capacity it can support before clipping eats into the benefit.
The same loss curve, run in reverse
This tool uses the same clipping curve as the DC to AC ratio calculator, fitted to published results: essentially no loss up to a 1.10 ratio, about 1.1% at 1.3, 2.2% at 1.4, and 3.5% at 1.5, rising faster beyond that. One study co-authored by NLR and Sandia researchers found fixed-tilt systems at the 1.34 median ratio clip about 1.4% of their DC energy, close to what the curve gives there. Instead of asking what a given ratio costs in lost output, this tool asks the inverse question: what ratio, and therefore what array size, keeps the loss under a chosen number.
Why a small amount of clipping is often the right answer
A moderate DC/AC ratio usually increases total annual output despite some clipping, since the extra panel capacity captures more energy during the long hours of low and moderate sunlight than it loses during the brief midday clipping window. A 0% tolerance is the safest choice but often leaves real output on the table compared to a mildly higher threshold.
Where the threshold stops being worth it
Losses climb slowly at first, then faster: this calculator gives 1.1% at a 1.3 ratio and 3.5% at 1.5, and a ratio above roughly 1.4 is where clipping becomes a deliberate design tradeoff rather than a minor side effect. Each added panel past that point still adds some energy, but less than the one before it, so the question becomes whether the panel's cost is worth the smaller gain. Real losses can run higher than a simple model suggests, because NREL's work on subhourly clipping notes that hourly weather data understates clipping loss by roughly 0.4 points at a 1.25 ratio and 1.5 points at 1.5. Once you have a ceiling, the kW to panel count converter confirms the exact system size.
The AC rating you enter sets the whole ceiling
The maximum array scales directly with the AC figure, so entering a datasheet's peak or maximum rating instead of the continuous one inflates the ceiling by the same percentage. A 7.6 kW inverter listed with an 8 kW maximum would add about half a kilowatt of phantom capacity at a 1% tolerance. The inverter continuous vs peak rating calculator shows which number to use, and the string length vs panel count calculator checks that the resulting panel count also wires correctly across your strings.