Solar tiles and slates look like the ideal answer for a new home: the roof generates electricity and nobody can tell. They do have drawbacks, and it is worth knowing them before you specify one. For how a BIPV solar roof compares with in-roof panels overall, including planning and Part L 2026, see the comparison guide.
1. It costs more per kWp
Tile and slate products carry interlocking edges and weatherproofing on every unit. A 2022 guide to building-integrated PV on self-build.co.uk puts it plainly: BIPV modules are "a little more expensive per kWp" than building-applied panels, and solar tiles are "more expensive than panellised" systems. Part of the difference is offset because the PV replaces roof covering you would otherwise buy, so compare quotes net of that credit.
2. It generates less per square metre
A small tile has proportionally less active cell area than a full-size panel, so the same area of roof carries fewer kWp. Under Part L 2026 the target is an output equal to a reference array of 0.22 kWp/m² over 40% of the ground floor area, so a lower-density tile system needs more roof to reach it. On a compact house with a small or complicated roof, check early that the target is achievable.
3. It runs warmer
Tiles and slates sit close to the roof structure with little air moving behind them, while panel arrays have a ventilation gap. PV output falls as cell temperature rises, so an integrated roof gives up a little output on hot days.
4. Repairs need matching units
If a tile or slate is damaged, the replacement has to match both the look and the electrical characteristics of its neighbours. Ask for spare units from the same batch at handover, and ask what happens if the manufacturer discontinues the range.
5. Fewer installers can fit it
A BIPV roof needs roofing and electrical skills working together, and some products are fitted only by installers trained by the manufacturer. Check that the installer and the specific product are MCS certified, because the MCS certificate is what lets the homeowner claim Smart Export Guarantee payments.
6. Fire performance is declared, not pass or fail
Roof-integrated mounting kits are tested under MCS 012, which covers wind loading, reaction to fire and resistance to water penetration. For kits that replace the roof covering, the fire test is test-and-declare: the product states its rating rather than simply passing. Check that the declared rating suits the building and its position on the plot.
When the drawbacks do not matter
In a conservation area, within the curtilage of a listed building or on a design-led custom build, the alternative may be no solar at all or a design the planners will not accept. There, the cost and output penalties are the price of getting PV onto the roof, and the roof-covering credit narrows the gap. On a volume site with no design constraints, in-roof panels are usually the better buy.
