Installation · Guide
In-roof vs on-roof solar panels: pros, cons and leaks
Most home solar panels are on-roof: fixed on rails above the tiles or slates. In-roof panels, also called integrated panels, sit in the roof itself and replace the tiles where they go.
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Two types
What in-roof and on-roof mean.
This guide compares them, explains how each can leak, and says what to do about water in your loft.
- On-roof (above-roof). MCS describes these as panels mounted above the roof covering without replacing it. Hooks or brackets fix to the rafters and come out between the tiles.
- In-roof (roof-integrated). The panels or their mounting kit replace some or all of the roof covering. The panels sit in a tray or flashing kit, with tiles or slates laid back around the edges.
- Solar roof tiles are a different product. The Energy Saving Trust says they typically produce about 80% of the electricity of panels on the same area.
In-roof kits are for pitched roofs: one manufacturer’s is for slopes of 12 to 50 degrees. Flat roofs use frames instead: see solar panels on a flat roof.
Pros and cons
The pros and cons of each.
- Looks. In-roof panels sit in the plane of the roof, so they look neater. On-roof panels stand above the tiles.
- Birds. Historic England notes that pigeons nest under panels, causing problems with panels and cabling. In-roof panels leave no gap underneath. On-roof arrays can have guards fitted: see bird proofing.
- Heat and output. Panels produce a little less when hot. Historic England says air should move behind an array so heat doesn’t build up, and one in-roof maker accepts in-roof panels run warmer than panels on rails.
- Weight. On-roof panels add weight on top of the tiles. In-roof systems replace tiles, which offsets some weight. MCS requires the roof structure to be checked either way.
- Fire and repairs. An in-roof system is part of the roof covering, so MCS requires it to be fire tested, and the rating usually applies only to the panel family tested. If a panel fails and that model has gone, a replacement can be harder to find.
Cost and new roofs
Cost, new builds and re-roofs.
The Energy Saving Trust lists integrating the panels into the building, and renewing the roof covering, among the things that affect cost.
- On a sound existing roof, on-roof panels go over the tiles you already have.
- In-roof panels mean the tiles under the array come off and the kit is weathered in around its edges. Manufacturers design them to go on as part of a roofing job, for re-roofs and new builds. If existing panels have to come off for roof work, see solar panel removal and refit.
- If your roof needs re-covering soon, decide on solar at the same time, so panels don’t come off again later.
Compare the two for your roof on a clear written quote. We install solar PV across England, Wales and southern Scotland: see solar panel installations and how many solar panels do I need?
Planning
Planning permission and conservation areas.
The planning rules we’ve read don’t treat in-roof panels separately, but they differ across the UK:
- England. Panels on a house are usually permitted development if they project no more than 200 mm from the roof slope and stay below the highest part of the roof. In a conservation area or World Heritage Site they can’t go on a wall, balcony or roof enclosure fronting a highway, and listed buildings aren’t covered. These rules changed on 27 August 2026.
- Wales also uses a 200 mm limit. In a conservation area, panels on front or side walls visible from the highway need consent, and listed buildings are likely to need listed building consent.
- Scotland allows up to 1 metre from the roof. Listed buildings aren’t covered, and in a conservation area panels need to go on the rear, or a side that doesn’t front a road.
Historic England says roof-integrated PV generally doesn’t suit prominent roof slopes of listed buildings. If unsure, ask your council.
In-roof leaks
How in-roof systems leak.
If your in-roof solar is leaking, the weathering around the panels is the usual suspect. MCS 012, the standard for roof mounting kits, requires every in-roof kit to be tested in wind-driven rain, and names where water most often gets in:
- over or through the flashings, where the kit meets the tiles or panels, or at joints between flashing pieces;
- through gaps the kit has opened up in the tiles or slates around it;
- through the underlay, wherever something passes through it unsealed.
Fitting matters as much as the kit. One manufacturer’s instructions require a proper underlay, tiles resting on the flashings with enough overlap, and a roof steep enough for water to run off the top flashing. They also recommend checking occasionally for debris settled into the system.
On-roof leaks
How on-roof systems leak.
On-roof fixings pass between the tiles. Historic England describes the usual method: hooks are fixed to the rafters, and the tile above each hook is notched underneath so it sits back down. Leaks start where that goes wrong:
- Lifted or cracked tiles. A tile that isn’t notched properly, or that a hook presses on, can sit high or crack. MCS requires tiles and slates to be notched or flashed so no new gaps are left.
- Drilled slates. Historic England says slates should never be drilled to fix brackets, as it risks cracking them and letting water in.
Water in the loft
Water in your loft? What to do.
It isn’t always a leak. Condensation can form under a roof that isn’t ventilated well enough, and since 2024 NHBC has treated new-home roofs with in-roof arrays as airtight when designing ventilation. Condensation often shows on cold mornings rather than in heavy rain.
- Stay off the roof, and don’t lean out of windows to look. HSE says almost one in five deaths in construction work involve roof work.
- Check the loft only if it’s safe. Use a torch, stand on boards, never between the joists, and keep clear of the inverter, isolators and cables. If water is near electrical equipment, don’t touch anything. If there is any sign of fire, call 999.
- Catch the drips in a container.
- Photograph it: the wet patch, the timbers above, and where it lines up with the panels. Note the date and the weather.
- Look from the ground for slipped or cracked tiles, loose flashing or storm damage.
- Call someone. For a new build, try the builder first: on NHBC-registered homes, builders must put right defects reported in the first two years. For a recent system, contact the installer.
We repair and service solar systems fitted by any installer, across England, Wales and southern Scotland. Our engineers can check the system and tell you what’s causing the problem. Work on a sloping roof usually needs scaffolding. You get a clear written quote before any work starts. See solar panel repair and solar panel servicing.
Buying a house with in-roof panels? See buying or selling a house with solar panels.
Sources: MCS 012 and MIS 3002; Energy Saving Trust; Historic England; the Planning Portal, Welsh Government and Scottish Government planning guidance; NHBC; HSE; in-roof kit makers’ installation guides.
Questions
The things people ask before they ring.
Not answered here? Call 0800 156 0191, Monday to Friday, 9:00am–5:00pm.
Are in-roof solar panels less efficient?
They can be slightly. Panels lose a little output as they warm up, and in-roof panels have less air behind them. How much depends on the kit and the roof.
Are in-roof solar panels more expensive?
It depends on the roof. On a sound roof, on-roof panels leave the tiles in place. On a new roof or re-roof, in-roof panels replace tiles that would otherwise be bought. Compare both on a clear written quote.
Do roofs with solar panels leak?
They shouldn’t. MCS says a system must not harm a building’s weather tightness for its whole life. Leaks usually come from flashing on in-roof systems, or from lifted, cracked or drilled tiles and slates on on-roof ones.
Can you have in-roof solar panels on a slate roof?
Yes, with a kit made for slate. Manufacturers must declare which roof coverings their kits suit, and one says its in-roof system works on slates as well as tiles.
Ready when you are
Water in the loft, or planning a new roof?
We’ll call you back to talk it through, and you get a clear written quote before any work starts. Mon–Fri 9:00am–5:00pm.