In-roof solar panels: are they better than on-roof?

What are in-roof solar panels?

In-roof solar panels, also called integrated, roof-integrated or flush solar panels, sit in the plane of a pitched roof: the kit replaces the tiles over its area and becomes the roof covering there, which MCS calls "forming the main roof covering" [1]. On-roof panels are fixed on rails or brackets above the existing tiles. On pitched roofs, MCS installers are to use kits certified under MCS 012 for both, unless none suits and MCS's conditions for another system are met [1][4]. Solar roof tiles are a separate product, covered in solar tiles, and panels with an integrated micro inverter (a small inverter on each panel) are a different idea again.

Are in-roof solar panels better?

Neither is better in every case; they trade appearance and timing against output and simplicity. Side by side, from MCS's installation standard and the other sources cited:

The planning row is for England. Planning rules for Wales, Scotland and Northern Ireland are in do you need planning permission for solar panels, and building rules differ too: MCS points Scottish installers to the Building Standards Technical Handbook and Northern Irish ones to the Technical Booklets [1].

Do in-roof panels make less electricity?

A little, because they run warmer. PVGIS, the European Commission's solar tool, models two extremes: panels with air flowing freely behind them, and panels completely built into a roof with no air movement behind them, which it says can run considerably hotter [6]. Comparing the two extremes, the built-in case made 2.7 to 3.1 per cent less a year in our five places and three layouts (south at 35 and 30 degrees, south-east at 35), by our calculation [5]. The manual says some mountings fall between the two and perform in between [6]; on-roof panels are not fully free-standing either, so the gap between two real systems is likely smaller.

How much do in-roof solar panels cost in the UK?

The government's cost tables do not split prices by how panels are mounted, so they give no in-roof price [7]. They do separate new homes from existing ones. From April 2025 to March 2026, MCS-registered domestic installations up to 4 kW in Great Britain with valid cost data cost a mean of £1,518 per kW of total installed capacity (TIC) on new homes (21,414 installations) against £2,109 on existing homes (60,713); the costs include VAT where it applied and exclude extended warranties and any other material or works carried out on the solar equipment [7]. The data give no reason for the gap and do not say how many of either were in-roof, so they are not an in-roof price.

Compare two quotes. When re-roofing, ask for in-roof as part of the new roof, and for the new roof plus on-roof panels.

When is in-roof not worth it?

On a sound roof with years of life left, in-roof means taking off tiles that do not need replacing, because the kit becomes the covering [1]; on-roof panels leave the roof covering in place. The next step there is a quote for on-roof panels. In-roof also depends on the kit suiting the roof: one maker states its kit is MCS accredited at 15 degrees pitch [13].

New builds and the Future Homes Standard

In England, the Future Homes Standard adds a new legal requirement for new homes. When a home is built, a system for renewable electricity generation is to be installed on the building or within its grounds, which the government expects to mean solar panels in most cases [8]. There are limits: buildings with a storey at least 18 m above ground are exempt, a directly connected off-site system giving equivalent output can count instead, and the guidance says no panels are needed if the available roof cannot produce 720 kWh a year [8].

Key dates, England. The new rules come into force on 24 March 2027 for most new homes and on 24 September 2027 for higher-risk buildings, subject to transitional provisions [8].

We found nothing in the government response on whether panels should be in-roof or on-roof, so ask the developer which they fit, and get the kit's certificate with the handover documents.

Fire rating: the check to ask about

Which are the best integrated solar panels for your roof? There is no single answer, but two checks come first: the kit is certified for your roof's pitch, and its fire rating suits where it sits. MCS installers shall be able to show that an installation has not affected the roof's fire performance; for an in-roof kit, MCS's note gives a kit with a fire rating appropriate for the array's location as the way to show it [1]. Ask for the fire classification of the exact panel and mounting-kit combination, and for confirmation that it suits your building, its position on the roof and its distance from the relevant boundary. In England, Approved Document B classifies roof coverings with the Test 4 suffix, for example BROOF(t4), and says Test 4 is to be used [11]; a rating from a different test is not the same thing. How close to the boundary a lower-rated covering can go also depends on the building: in England, for example, some ratings are not acceptable on a terrace of three or more houses [11]. Wales has its own Approved Document B [12], Scotland uses its Building Standards Technical Handbook and Northern Ireland Technical Booklet E [1], so ask the installer to show how the design meets your nation's rules for the whole roof. Makers publish ratings for their own tested systems: one states its in-roof system is tested to BROOF(t4) [13]; another that its 445AG panel and its own mounting kit, tested together, are classified BROOF under Test 4, the UK test, and are listed on its MCS certificates [14]. Each rating applies to the combination that was tested, not to other panels or kits. In England, building regulations normally apply to roof panels, including the roof's load and the electrical work [10].

What to ask the roofer and installer

1. Which kit, and is this panel and kit combination on its MCS 012 certificate?
2. Its fire rating, and does it suit this building and how close the roof is to the boundary under your nation's building rules?
3. The roof pitch the kit is certified for, against your roof.
4. Who is responsible for weather tightness where the kit meets the tiles, and for how long?
5. The roof warranty: if the roof is under warranty, has the provider been consulted, and will you be asked to agree in writing before work that may invalidate it?
6. Both prices: in-roof as part of the roof, and on-roof, so you can compare.

How a solar installation goes from survey to switch-on is in solar panel installation; the planning rules are in do you need planning permission for solar panels.