Is My Roof Right for Solar? The 2-Minute Checklist

Cornwall has some of the best solar irradiance in mainland England — but irradiance only matters if your roof can use it. The checklist below covers what an MCS surveyor actually assesses. It takes about two minutes if you can picture your roof, and it tells you whether to expect an easy quote, a caveated one, or a polite "have you considered ground-mount?".

The checklist

• My roof faces somewhere between south-east and south-west. Due south is ideal; SE and SW give up only 5–10% of yield. East–west roofs can still work with panels split across both slopes — north-facing roofs are where the conversation ends.
• The pitch is somewhere near 30–40 degrees. Most Cornish pitched roofs land in this sweet spot naturally. Shallower or steeper still works with modest yield loss; flat roofs need tilt frames and a wind-loading check — very doable, slightly dearer.
• Nothing shades the roof for big parts of the day. Chimneys, dormers, mature trees, the neighbour's taller gable — shade on even one panel drags down a string. Persistent partial shade isn't fatal (optimisers and microinverters exist) but it must be designed around, not discovered later.
• The roof covering has 25+ years of life left. Panels are warranted for 25+ years, and taking an array off to re-roof underneath it is money down the drain. Tired felt, slipped slates or crumbling battens? Re-roof first, then panel. Slate itself is fine — it just needs slate hooks and adds 15–20% to install cost.
• There's a clear, unbroken area of roughly 20m² or more. A 4kW system needs around 10 panels at about 2m² each. Velux windows, vents, chimneys and hips all eat usable area — count the clean rectangle, not the whole slope.
• Someone's home in the daytime — or could shift usage there. Solar pays best when you use it as you make it: home working, EV charging, heat pump, immersion diverter, timer-run appliances. All-out-all-day households lean harder on a battery to make the maths work.
• I know my EPC rating (or can find the certificate). Not a blocker for solar itself, but surveyors ask, some export tariffs and lenders care, and solar typically improves it — useful for holiday-let compliance and future sale paperwork.
• The property isn't listed, and isn't in a conservation area — or I know the constraints if it is. Listed buildings always need listed-building consent; conservation-area homes (parts of Truro, Falmouth, Penzance, St Ives) may need planning where panels face the street. Not fatal — rear slopes and in-roof panels get consented regularly — but it adds months, so flag it early.

Ticked all eight? You're a solar surveyor's easy Tuesday

Expect a straightforward survey, a firm quote around the ranges in our Cornwall cost guide, and one to three days on the roof. Get two or three written quotes from MCS-certified installers and enjoy being fought over.

Couldn't tick something?

Orientation or shading doubts: this is precisely what a free survey resolves — surveyors model your actual roof and horizon rather than guessing. East–west splits and optimiser layouts rescue plenty of "imperfect" roofs.

Roof condition or space: an installer will tell you honestly whether to re-roof first, use fewer higher-output panels, or consider a garden ground-mount or outbuilding roof instead.

Listed or conservation status: read planning constraints as a schedule item, not a refusal. Your installer should confirm the planning position before quoting — ours do.

Daytime usage: a battery converts an away-all-day household into a strong solar case — store the midday generation, use it after dark.

Want the numbers first? The 2026 Cornwall solar cost guide covers prices by system size, and the Tesla Powerwall guide covers the battery question in depth.