How microinverters change the shading math
Microinverters versus string inverters
With a string inverter, panels are wired together and the whole string drops to the output level of its most shaded panel, while microinverters let each panel convert its own power independently, so a shaded panel only loses its own output. That's the core reason this calculator works panel by panel instead of applying one derate to the whole array, similar in spirit to the panel-level comparisons in the power optimizer output calculator. A NLR study of shaded grid-tied PV systems found that in a standard series string, shading just one cell group can zero out that group's entire output, the exact failure mode microinverters are designed to contain.
What partial shading actually costs you
With microinverters, you lose roughly the shaded panels' own share of production times their shade loss percentage, not a system-wide penalty, so 4 out of 20 panels at a 60% shade loss costs around 12% of total output rather than dragging the whole array down. That's a meaningfully smaller hit than the same shading would cause on a string inverter setup.
Shading still matters, just contained
Microinverters don't make panel-level shading irrelevant. Each shaded panel still loses output relative to its own unshaded potential, microinverters just stop that loss from spreading to the unshaded panels around it. That containment is the whole value proposition compared to a string setup, and it's worth comparing against the annual output estimator if you're weighing microinverters against a simpler string design. If shading is significant enough to influence your overall system size and layout rather than just your equipment choice, the partial roof shading sizing adjustment tool addresses that broader decision.
Efficiency versus shading handling
Microinverters typically run in a similar efficiency range to string inverters, so the bigger difference in real-world output usually comes from how shading is handled rather than from raw conversion efficiency. NLR's PVWatts calculator, the industry-standard modeling tool behind most professional solar estimates, applies a similar inverter efficiency assumption regardless of inverter architecture, treating shading and orientation as the bigger variables in a real-world estimate. If your roof has little to no shading, the choice between the two matters a lot less for total output. For a broader look at real-world losses, see the real-world vs nameplate gap calculator.