Solar Shading Loss Calculator

Estimate how trees, chimneys, or roof features cut your solar output — and find out whether microinverters would pay for themselves on your roof.

% of roof area shaded

Estimate what fraction of panel area receives shade

When does shading occur?

Shading source

Inverter type

System size

Peak sun hours

hrs/day

Electricity rate

$/kWh

Shading is the most underestimated solar problem

Most solar quotes show you production estimates assuming full, unobstructed sunlight — the NREL PVWatts default. Real roofs in real neighborhoods have trees, chimneys, dormers, and neighboring buildings that create shade patterns that shift throughout the day and year. Missing this step can mean your system produces 20–40% less energy than the proposal said.

The string inverter multiplication effect

This is the most important thing to understand about shading and solar: in a traditional string inverter system, shading one panel out of 20 can reduce output from all 20 panels in that string. The shaded panel becomes a bottleneck because current must flow equally through every panel. A 5% shaded roof area can cause 25–40% total system loss — a five-to-eight-times multiplication of the actual shadow.

Panel-level electronics solve this

Microinverters (Enphase) and DC power optimizers (SolarEdge, Tigo) break the series-string dependency. Each panel operates at its own maximum power point, completely independently. Shading one panel in a 20-panel system only reduces that panel's output, not the other 19. On any roof with even occasional shading, the extra cost of panel-level electronics (typically $0.10–0.25/W more) pays back in 3–7 years through recovered production.

Frequently asked questions

How much do trees reduce solar production?

It depends on how much shading occurs and what type of inverter you use. Partial shading that covers 20% of a roof with a string inverter can cause 30–50% total system output loss, because one shaded panel drags down the entire string. The same shading with microinverters causes only about 20–25% loss, since each panel operates independently.

What is the difference between a string inverter and microinverters for shading?

In a string inverter system, panels are wired in series like a chain of Christmas lights — the weakest link (the shaded panel) limits the entire string output. Microinverters (Enphase) and power optimizers (SolarEdge, Tigo) allow each panel to harvest its maximum possible power independently, so a shaded panel only affects its own output, not the whole system.

Should I cut my trees to improve solar output?

It depends on the dollar value of the shading loss vs the cost and ecological loss of removing trees. For mature shade trees, removal typically costs $1,000–$3,000 each. If shading is causing $200/yr in production loss, it takes 5–15 years to recover tree-removal costs — often longer than the upgrade to microinverters would cost. Microinverters are usually the better economic choice.

What is the best inverter for a shaded roof?

Enphase microinverters offer the best shading mitigation because each panel has its own inverter with independent maximum power point tracking (MPPT). SolarEdge with power optimizers is a strong second choice. String inverters are only appropriate for roofs with zero shade — full sun exposure throughout the day.

Can solar installers model shading before installation?

Yes — reputable installers use software like Aurora Solar, Helioscope, or PVWatts to model your specific roof shade profile using satellite imagery and sun-angle data for your latitude. Ask to see the shade report as part of any proposal. If an installer doesn't model shading, that is a red flag.