Solar PV Panels

Filling a roof is easy. Filling it well is the job

Most solar quotes are a packing exercise: count the tiles, count the panels, print the number. A well-designed array is a different piece of work. Strings are planned around shading measured through the day rather than guessed at from the pavement, the array is kept clear of the roof edges where wind uplift is highest, and there is room left to work if a panel ever has to come off.

Roof penetrations are flashed and weathered properly. Panels will be up there for twenty-five years or more, so if the roof underneath has only a few years left in it we will tell you before we fix rails to it — not after.

Mounting options

• On-roof — rails fixed to the rafters through flashed penetrations, panels sitting above the tiles or slates. The standard approach: quickest, cheapest, and the ventilation gap behind the panels helps them run cool.
• In-roof — panels set into the roof plane in place of tiles, with a proprietary tray system underneath. Noticeably tidier, usually preferred on new build and often the route to consent in a conservation area. It costs more and runs slightly warmer.
• Flat roof — ballasted A-frames or east-west “butterfly” layouts. No penetrations, but the wind loading calculation matters and so does whether the roof can carry the ballast.
• Ground-mounted — where there is land and the roof is wrong. Better access for cleaning and maintenance, ideal orientation, but a trench, a longer cable run and, above a certain size, a planning application.

Orientation, pitch and what they are actually worth

South-facing at around 35° gives the highest annual total. That is not the same as the best system for your house. An east–west split array generates across the morning and the evening rather than piling everything into the middle of the day, and if the house is empty from nine until six that shape of generation is often worth more to you than a bigger midday peak you export at seven pence.

We model your specific roof — orientation, pitch, location and measured shading — using the standard MCS methodology, and give you an annual kWh estimate alongside a self-consumption estimate. The second number is the one that decides your bill.

Shading, strings and optimisers

Panels in a string behave a little like a row of taps on one pipe. Shade one and you can drag down everything wired with it. Chimneys, dormers, aerials, satellite dishes, flues and the neighbour’s sycamore all do this, and they do it at different times of day and different times of year.

Two things follow. First, string layout is a design decision that should be made after the shading survey, not before. Second, optimisers — per-panel electronics that stop one shaded module dragging its neighbours down — genuinely earn their money on some roofs and are sold as a default upsell on plenty of others. We will tell you which of the two you are looking at, and why.

Panels we fit

We specify tier-one monocrystalline modules with full-black framing where appearance matters, and we choose on warranty terms and degradation rate rather than headline efficiency. A panel that is half a percent more efficient on a datasheet is worth far less than a string that is not shaded at two o’clock in October.

Product ranges change frequently, so rather than pin this page to a model number we will put the exact modules, inverter and mounting system in your written proposal, with the datasheets attached.

Bird and debris protection

Pigeons nest under arrays and make a mess that is cheap to prevent and expensive to fix. Where they are a known local problem we mesh the array perimeter at installation. It is worth asking any installer whether their quote includes it.

Planning permission

Most domestic roof-mounted solar in England falls under permitted development, subject to conditions on how far the array projects and where it sits. Listed buildings, conservation areas, flats and larger ground-mounted arrays are the common exceptions. We flag anything we spot at survey, but the final position rests with your local planning authority.

What panels alone will and will not do

An array with no storage typically means you use somewhere around a quarter to a third of what you generate and export the rest, and exported power earns a fraction of what it costs to buy back. That can still be a sound investment — particularly if someone is home during the day — but it is why we ask about your evenings before we count panels. Battery storage is what moves that figure, and an EV charger moves it again.

Send us your annual kWh figure and a photo of the roof and we will tell you what is realistic before anyone visits.

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