In-Roof Solar Panels

In-roof solar panels replace part of your roof covering rather than sitting above it on brackets. MCS calls this a "roof integrated installation" and defines it as "an installation where the solar panels or roof mounting system (or an individual component of a roof mounting system) replaces some or all of the roof covering". The array ends up flush with the tiles instead of standing proud of them. It looks better, it usually costs more to retrofit, and it is tested to a noticeably harder standard than a normal on-roof system. There is also one moment in a house's life when the extra cost of going in-roof nearly disappears.

This page covers what changes when the panels go into the roof instead of onto it: the certification, the fire rule that can dictate where on your roof the array is allowed to sit, the cost drivers the Energy Saving Trust actually names, and the planning position in England. Everything below was verified on 20 August 2026 against MCS 012 Issue 3.0, both current versions of MIS 3002, the Energy Saving Trust, HMRC VAT Notice 708/6 and the Town and Country Planning (General Permitted Development) (England) Order 2015.

What in-roof actually means, in the standard's own words

MCS splits domestic pitched-roof solar into exactly two categories, and the dividing line is whether the roof covering is replaced. MCS 012 Issue 3.0, The Solar Mounting Standard, dated 10 May 2023, defines both:

• Roof integrated installations are "an installation where the solar panels or roof mounting system (or an individual component of a roof mounting system) replaces some or all of the roof covering".
• Above roof installations are "an installation where the solar panel is mounted above the roof covering and the installation system does not replace or significantly alter the roof covering beneath it".

In practice, an in-roof job means the installer strips the tiles or slates from the array footprint, fits a moulded tray or flashing system into the gap, drops standard PV modules into it, and dresses the surrounding tiles into the flashing. The finished roof has a rectangle of glass where the tiles were, sitting at roughly the same level as the covering around it. An on-roof job leaves every tile in place and lifts the panels above them on hooks and rails.

The second half of that MCS definition is the bit that matters. Because the mounting system replaces the roof covering, the mounting system is the roof covering across that area. Everything the tiles were doing about wind, rain and fire is now the kit's responsibility, and the standards treat it accordingly.

In-roof is not the same thing as solar roof tiles

An in-roof system uses ordinary rectangular PV modules held in a tray. Solar roof tiles are PV built into individual tile-shaped or slate-shaped units that lay like a roof covering. Both are "integrated" in the loose sense and both end up flush, but they are different products at different prices, and MCS certifies them under different standards.

MCS 012's scope covers both, listing "products which enable roof integrated installations of solar panels" and, separately, "active solar products which become part of the roof covering in roof integrated installations. This includes PV tiles and other products where PV elements are bonded to roof coverings such as standing seam roof sheets. Such products would also require certification in accordance with MCS 005." Bespoke building-integrated products go further again, under MCS 017. Our guide to solar roof tiles in the UK covers that end of the market.

If you want the flush look at the lowest cost, in-roof with standard modules is the cheaper of the two routes, because the panels themselves are the same mass-market modules used on every on-roof install. You are paying for the tray, not for bespoke glass.

The certification difference nobody explains at the quote stage

Every roof integrated system has to be fire tested and weathertightness tested to earn MCS certification. An above-roof system only has to be tested in specific circumstances. This is the single biggest technical difference between the two routes, and it is written into MCS 012 Issue 3.0 in two flat sentences.

On fire, clause A2.1 states: "All roof integrated systems shall be tested." For above-roof mounting, clause A2.2 requires testing only where the components "increase the gaps in a discontinuous roof covering more than would be the case without the mounting system", or are made from an organic material and are either inserted through gaps in the covering or replace part of it. A metal roof hook on a tiled roof frequently falls outside all three triggers.

On water, clause A3.5 states: "All roof integrated systems shall be tested." Above-roof products are tested only where they penetrate a continuous covering (A3.6) or are inserted between the gaps of a discontinuous one (A3.7).

The weathertightness test itself is not a token. For roofs pitched above 10 degrees, MCS 012 requires the wind-driven rain methods of PD CEN/TR 15601:2012, and specifies sub-tests B and D from a set that covers "a range of severe UK coastal conditions". A sample section of roof is built, sprayed continuously, blasted with calibrated wind at 10 metres per second, run-off water applied at the top, and the air pressure across the specimen stepped up and down while leakage is measured. Clause A3.14 requires the test to be run "at the minimum pitch of the roof covering/solar panel combination", meaning the worst case rather than a flattering one.

MCS is candid about where an in-roof system leaks when it does. The standard's own note lists the biggest risks for roof integrated products as "the risk of water entry over the flashing system which is around, between and, in some cases, under the panels", at the interface with the roof covering, at the interface with the panels, or through joints in the flashings.

So a certified in-roof kit has been through more testing than a certified on-roof kit. That is reassuring. The flip side is that an uncertified in-roof arrangement, or a certified kit used with a roof covering it was never tested against, strips away the only evidence anyone has that your roof will stay dry. Clause A3.8 requires the manufacturer to declare which generic classes of roof covering the system can be used with, listing single lapped pantiles or plain tiles, double lapped plain tiles, double lapped slates, profiled or standing seam metal sheet, and any other generic type. Your roof needs to be on that list.

Your installer is required to use a certified kit, with one narrow exception

MIS 3002, the Solar PV Installation Standard, requires certified mounting products for both routes. The clause is short: "Solar PV systems mounted above, or integrated into, pitched roofs shall utilise products tested and certified according to MCS 012 Pitched Roof Installation Kits." Both current versions of the standard are dated 18 March 2026, and MCS states that "compliance with this Standard becomes mandatory for MCS installers certified in accordance with MIS 3002 from 18 June 2026".

One thing to know before you quote a clause number at anyone. MCS currently publishes MIS 3002 as two parallel documents: Issue 6.0 for the current installer scheme, and MIS 3002:2025 Issue 2.0 for the redeveloped installer scheme. The wording of the clauses below is effectively identical in both, but the numbering is not: the current-scheme document uses a 5.x prefix where the redeveloped-scheme document uses 3.x. We give both numbers throughout, so the requirement above is clause 5.5.2 (current scheme) or 3.5.2 (redeveloped scheme). Ask your installer which scheme they are certified under if you want the exact reference.

Clause 5.5.5, or 3.5.5 in the redeveloped-scheme document, provides the exception, and it is worth knowing because in-roof kits are a narrower market than on-roof rails. It is also the clause MCS specifically rewrote in the March 2026 update. Where an installation falls outside MCS 012's scope, or where no certified mounting system suits the job, an uncertified system may be used only if the contractor can evidence all six of the following:

• The install keeps the building compliant with current Building Regulations for structural safety, fire safety and weathertightness. The standard names the documents per nation: Approved Documents A, B and C in England and Wales; Sections 1, 2 and 3 of the Building Standards Technical Handbook in Scotland; and Technical Booklets D, E and C in Northern Ireland.
• A structural assessment and a wind loading calculation have been completed for the specific mounting system, based on manufacturer calculations, a third-party structural engineer or an appropriate software platform.
• The customer has been told they should get an updated Fire Risk Assessment to confirm the roof's fire performance has been maintained.
• There is evidence of how the weathertightness of the roof has been maintained, which "may include photographic records, installation method statements, and/or confirmation that existing warranties remain valid, and that the quality is no less than if an MCS 012 certified mounting system was used".
• The components are evidenced as compatible with one another.
• The system is installed in accordance with the manufacturer's instructions, for every component, "even when supplied from different manufacturers".

Two related clauses matter on an in-roof quote. Clause 5.5.3, or 3.5.3, requires that all mounting components "shall be specifically approved to work together unless described by the manufacturer as universally compatible", and clause 5.5.4, or 3.5.4, is blunter: "Where mounting systems are certified or listed using a named PV module or modules then only those modules shall be used." In-roof trays are moulded to particular module dimensions. If your installer offers to swap the panel model after the tray is specified, that clause is the one to quote back.

The fire rule that can decide where on your roof the array is allowed to sit

Because an in-roof kit becomes the roof covering, its fire classification interacts with how close your roof is to a boundary. On a terrace or a tight semi, that can restrict where the array goes. This constraint does not exist in the same way for a standard on-roof system fitted over concrete or clay tiles.

MIS 3002 clause 5.8.1, numbered 3.8.1 in the redeveloped-scheme document, requires the contractor to "demonstrate that the installation of the modules has not affected the fire performance of the roof", and gives two ways to do it: "(a) Mounting above an existing non-combustible roof covering (pitched roofs)" or "(b) Where in-roof (forming the main roof covering) using an in-roof kit with the appropriate fire performance rating for the proposed location of the array."

Route (a) is the easy one. Concrete or clay tiles are non-combustible, so a normal on-roof array over them is done. Route (b) sends you to the fire classification table from Approved Document B, which applies in England and Wales, and to the worked example MCS reproduces. Here is what those classifications mean for a semi-detached pair with a 1,000 cubic metre capacity, bounded on three sides by other properties and on the fourth by a road, where d is the distance to the relevant boundary:

Read the middle row again, because it is the one that bites. A D-rated or E-rated in-roof kit on a house 8 metres from the boundary cannot be laid as one continuous array. It has to be broken into patches of no more than 3 square metres with 1.5 metre tiled gaps between them, and those gaps themselves have to meet a classification of no less than A2-s3, d2. On a typical 20 to 30 square metre domestic array, that is a completely different roof layout and a completely different quote.

This is why the fire classification of the specific kit belongs on your quote, next to the panel model, rather than buried in a folder you never see. Ask for it in writing.

One footnote for anyone reading the standard alongside this page, because the two parallel documents diverge here. Both versions of the clause tell you to "See Appendix C for a worked example and guidance on fire classification relevant to distance from boundaries reproduced from Approved Document B". In the current-scheme Issue 6.0 document that is right: Appendix C is the Fire Rating Worked Example. In the redeveloped-scheme MIS 3002:2025 Issue 2.0, the appendices were cut down to three and Appendix C is the commissioning templates, while the fire rating worked example sits at Appendix A. The cross-reference was carried across without being renumbered. If you go looking for the fire table in the 2025 document and find handover paperwork, you are in the right document and the wrong appendix.

What in-roof costs, and the two moments the premium nearly disappears

No UK body publishes an in-roof premium, but the Energy Saving Trust names building integration as a cost driver in its own list, and names the two situations that bring the cost down. Anything more precise than that would be a number someone made up, so here is exactly what the Trust does say.

Its solar panel guidance, last updated 13 August 2026, puts a typical domestic system at "around 4.5 kWp" costing "around £7,600", covering 20 to 30 square metres with around 12 panels. It then lists what moves that price:

• the size of system
• any difficulty accessing your roof
• whether you choose panels or tiles
• whether you integrate the panels into the building
• whether you need to renew the roof covering

Three of those five bear directly on an in-roof job. And then the Trust adds the line that matters most here: "You can lower the cost of installation costs if you already have scaffolding up for roof repairs or if you're building a new house."

That is the whole economic case for in-roof, in one sentence. The extra cost of going in-roof on an existing roof is largely the cost of stripping and disposing of tiles you already own, fitting a tray, and re-dressing the surrounding covering, on top of scaffolding you are paying for anyway. If the roof is coming off regardless, because it is being re-covered or because the house has not been roofed yet, most of that work is happening either way. You are then choosing between paying a roofer to lay tiles across an area, or paying for a tray in the same area. The gap narrows sharply.

The reverse is also true and worth saying plainly. Retrofitting in-roof onto a sound roof that has 20 years left in it means paying to remove a working roof covering for aesthetic reasons. On a front elevation that is a perfectly good reason. Just make it a decision with the number in front of you, rather than a default. Our guide to solar panel costs in the UK sets out the baseline an in-roof quote should be measured against, and our walkthrough of the installation process covers what the scaffolding and survey stages involve.

Planning permission in England: in-roof clears the height rule easily

In England, permitted development for domestic solar is lost if the equipment protrudes more than 0.2 metres beyond the roof slope. A flush in-roof array clears that comfortably, which is one genuine planning advantage over a bracket-mounted system.

Class A of Part 14, Schedule 2 of the Town and Country Planning (General Permitted Development) (England) Order 2015 removes permitted development where the equipment "would protrude more than 0.2 metres beyond the plane of the wall or, in the case of a pitched roof, the roof slope, when measured from the perpendicular with the external surface of the wall or roof slope". An on-roof system on hooks and rails typically sits somewhere in the region of 100mm to 150mm proud, so it is usually inside the limit too, but it is using up most of the allowance. An in-roof array is at or below the plane of the covering.

The second England condition favours in-roof as well. Condition A.2(a) requires that the equipment "is, so far as practicable, sited so as to minimise its effect on the external appearance of the building". A flush array is the easier case to argue where a planning officer is involved, for example on a property where permitted development rights have been removed by an Article 4 direction.

Three limits still apply in England whichever way you mount. Permitted development does not cover installation on a scheduled monument, or on a building within the curtilage of a listed building, and in a conservation area or World Heritage Site it does not cover equipment on a wall which fronts a highway. A listed building itself needs listed building consent regardless of how flush the panels are, and going in-roof does not change that, although conservation officers often prefer the flush appearance when consent is being negotiated.

Scotland, Wales and Northern Ireland each set their own permitted development rules, and the figures above are England only. Our guide to permitted development for solar panels takes the four nations separately.

VAT: the same zero rate, with one thing to check on the quote

Installing solar panels in the UK is zero-rated for VAT until 31 March 2027, after which the reduced rate of 5% applies. That is the same for in-roof and on-roof. HMRC's VAT Notice 708/6 sets out the relief for the installation of energy-saving materials in residential accommodation, and section 2.11 includes "photovoltaic (PV) panels with cabling, control panel and AC/DC inverter" within solar panels. The relief covers the installation service and the materials supplied by the person installing them. Materials supplied without installation are standard-rated.

The in-roof specific question is the roofing work. Stripping tiles, fitting flashings and re-dressing the covering is building work carried out to make the solar installation possible. Section 2.5.1 of the notice sets the test: "A single supply is where one element of the supply is the principal element to which all other elements are ancillary", and its worked example is cutting a new loft hatch to install loft insulation, which is treated as ancillary to the insulation. The notice gives no roof-specific example, so the honest advice is not to assume. Ask the installer to show how the roofing element is treated on the quote, before you sign. Our guide to VAT on solar panels covers the relief and the 2027 change in full.

What going in-roof does not change

Mounting choice has no effect on export payments, grid paperwork or the arithmetic of payback. Worth saying plainly, because in-roof is sometimes sold as though it were a different class of system.

• Export payments. The Smart Export Guarantee still requires an MCS-certified installation, and rates are still set by each supplier rather than by government. Our page on Smart Export Guarantee rates compares what suppliers currently pay.
• Grid notification. Your Distribution Network Operator still needs the G98 or G99 notification, and the Energy Saving Trust confirms the installer normally handles it, with NIE Networks the relevant body in Northern Ireland.
• The payback maths. Generation is driven by the size of the array, its orientation and shading, not by whether it sits in or on the roof. The Trust's payback table, based on July 2026 fuel prices for England, Scotland and Wales, gives 9 years in London, 9 in Aberystwyth, 10 in Manchester and 11 in Stirling for a household home all day, with export payments included. The import and export gap that drives those numbers is unchanged: Ofgem's price cap for 1 July to 30 September 2026 sets the average Direct Debit electricity unit rate at 26.11 pence per kWh, while the Trust puts typical export earnings at "around 12p for every unit that you don't use yourself".

If the in-roof premium is real and the generation is identical, the premium extends your payback by whatever the premium is divided by your annual saving. That is the calculation to ask for, and any installer quoting both options should be able to do it in front of you.

What to ask before you sign an in-roof quote

Five questions separate a properly specified in-roof job from an optimistic one. You do not need to understand the answers to ask them.

1. "Is the in-roof kit MCS 012 certified, and can I see it?" MIS 3002 clause 5.5.2, or 3.5.2 in the redeveloped-scheme document, requires certified products for integrated pitched-roof systems. If the answer is no, the six evidence requirements of clause 5.5.5, or 3.5.5, apply instead, and you are entitled to see all six.
2. "Is my roof covering on the kit's declared list?" MCS 012 clause A3.8 requires the manufacturer to declare which generic classes of covering the system is tested with. Plain tiles, pantiles, natural or synthetic slate and profiled metal sheet are all separate classes.
3. "What is the kit's fire classification, and how far is my array from the boundary?" The table above shows why. A D-rated or E-rated kit close to a boundary changes the array layout, not just the paperwork.
4. "Is the panel model the one the tray is certified with?" Clause 5.5.4, or 3.5.4, permits only the named modules where a mounting system is listed with them.
5. "What does the same system cost on-roof?" Get both prices on the same quote. That is the only way to see the premium you are actually paying for the flush look.

Get three quotes and compare the answers, not just the totals. Our guide to choosing a solar panel installer in the UK covers how to check certification and consumer-code membership, and you can request quotes through RenewQuote to start the comparison.

Frequently asked questions

All rules and figures on this page were verified on 20 August 2026 against MCS 012 Issue 3.0, The Solar Mounting Standard, dated 10 May 2023; MIS 3002, The Solar PV Installation Standard, in both of its current versions, Issue 6.0 for the current installer scheme and MIS 3002:2025 Issue 2.0 for the redeveloped installer scheme, both dated 18 March 2026 and mandatory from 18 June 2026; the Energy Saving Trust's solar panel guidance, last updated 13 August 2026; HMRC VAT Notice 708/6; Ofgem's published price cap for 1 July to 30 September 2026; and Schedule 2, Part 14, Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015. Standards, tax rates and planning rules change, and permitted development rights can be removed from an individual property, so confirm the position for your own roof before committing. RenewQuote is a quote comparison service and does not design, survey or install solar systems.