Should I avoid panels in the shaded zone entirely?

With string inverters: yes — one shaded panel affects the entire string. With micro-inverters: place panels there — they'll produce 70-90% of unshaded output without affecting other panels.

Shading Calculator: Output Loss

By Home Solar Guide Team|Updated 20 March 2026|educational

Independently written | Plain-English guide

Shading calculator — Chimney: 3-5% loss. Trees: 15-20%. Micro-inverters reduce losses by 60-80%.

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Panel count depends on your electricity use, roof space and direction — not on a rule of thumb. Get a recommended size and what it should cost.

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Find the right system size for your roof

Panel count depends on your electricity use, roof space and direction — not on a rule of thumb. Get a recommended size and what it should cost.

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How much output do you lose from shading?

Solar shading impact — quantified for common UK scenarios: CHIMNEY SHADOW (covers 1-2 panels for 2hrs/day): String inverter: 3-8% annual output loss (£30-£80/yr). With optimisers/micro: 1-3% loss (£10-£30/yr). TREE LINE (blocks morning sun until 10am): String: 15-25% loss (£150-£250/yr). With optimisers/micro: 5-10% (£50-£100/yr). NEIGHBOURING BUILDING (shadows bottom 2 panels afternoon): String: 10-18% loss (£100-£180/yr). With optimisers/micro: 3-7% (£30-£70/yr). SELF-SHADING (rows too close on flat roof): String: 5-10% loss. Solution: adequate spacing (minimum 1.5× panel height between rows). SEASONAL: Shading impact is 2-3× worse in winter (lower sun angle) vs summer. Annual figure is weighted toward summer (when most generation occurs). MITIGATION COST vs BENEFIT: Micro-inverters add £800-£1,200. If shading causes >8% loss: micro-inverters pay for themselves in 5-8 years. Sources: PVsyst shading methodology, manufacturer bypass diode performance data, academic studies.