A BIPV solar roof uses photovoltaic tiles, slates or modules as the roof covering itself, so the roof keeps the weather out and generates electricity. An in-roof panel array sits in a flush tray in place of the tiles it covers. Both count towards Part L 2026 if they deliver the required output; they differ on cost, output per square metre, appearance and planning. This page compares them for UK new builds.
What is a BIPV solar roof?
BIPV stands for building-integrated photovoltaics: PV that replaces part of the building envelope rather than being fixed on top of it. On a roof, that means the PV units interlock with each other and with the surrounding tiles or slates, and carry their own weatherproofing and drainage. Because the PV is doing the job of the roof covering, you do not buy conventional tiles or slates for that area.
The alternative is BAPV, building-applied photovoltaics: standard panels fixed on rails above a finished roof. BAPV is the usual retrofit approach. On new builds it is rarely chosen, because fitting the PV while the roof is being built makes an integrated system the simpler option.
Types of BIPV roof
- Solar tiles. PV units shaped to lay in courses with a matching tile range, so the array reads as part of a tiled roof.
- Solar slates. Slate-format PV units for slate roofs, often chosen where the neighbouring roofs are natural slate.
- In-roof panel systems. Full-size panels in an integrated tray that replaces the roof covering. Strictly these are BIPV too; in UK usage they are usually described separately as "in-roof", as on this page.
- PV glazing and facades. Glass or cladding units with integrated cells, used on roofs over glazed areas or on walls. Vertical surfaces generate less than a well-pitched roof.
BIPV tiles and slates
PV units that replace conventional tiles or slates course by course. The roof reads as an unbroken tiled or slated surface.
- ✓Closest match to a conventional roof finish
- ✓Often preferred in conservation areas and heritage settings
- ✓Replaces roof covering you would otherwise buy
- ✗Higher cost per kWp than panel systems
- ✗Fewer kWp per square metre, so more roof is needed for the same output
In-roof panels
Standard PV panels in a flush-mounted tray that integrates with the surrounding tile or slate. The lowest-profile panel installation.
- ✓Build-stage cost around £1,200/kWp
- ✓More kWp from the same roof area
- ✓The usual specification on volume sites
- ✗Visibly a solar array from the street
- ✗May be resisted by planners in sensitive settings
Cost: how to compare a BIPV solar roof with panels
Tile and slate products carry interlocking edges and integral weatherproofing on every unit, so they cost more per kWp installed than panel systems. The published build-stage benchmark for in-roof panels is around £1,200/kWp (Spirit Energy), against an MCS retrofit average of £1,565–£1,686/kWp for conventional systems. BIPV quotes vary more by product and roof, so compare like with like:
- the price per kWp and per square metre of roof covered;
- the credit for the conventional tiles or slates the PV replaces;
- whether labour, flashings, inverter, commissioning and MCS certification are included;
- the annual output in the design calculation, which is what Part L 2026 measures.
On a premium custom build the BIPV premium is a small share of the build budget and appearance often decides it. On a volume plot the same premium is harder to justify unless the planning context requires it.
Output: why tiles generate less per square metre
A solar tile or slate has proportionally less active cell area than a full-size panel, because each small unit needs its own frame, overlap and weather detail. The practical effect is fewer kWp on the same area of roof. Tiles also sit close to the roof structure, with less ventilation behind them than a panel array, and PV output falls as cell temperature rises. Compare products on their data-sheet kWp per square metre and on the modelled annual output.
How a BIPV solar roof counts under Part L 2026
Requirement L3 is output-based. Approved Document L 2026, paragraph 5.73, asks for an annual output at least equal to a reference PV array of 0.22 kWp/m² over 40% of the house's ground floor area (south-east to south-west, 45° pitch, not overshaded), or to an array covering the reasonably practicable roof area. The Approved Document does not distinguish between tiles and panels.
For a 42.5 m² ground floor, the reference array is 17 m² × 0.22 = 3.74 kWp. A panel system can usually reach that output on about that area of a south-facing roof. A lower-density tile system needs more roof to produce the same output, so check early that the roof is large enough, especially on a compact plan. The Part L 2026 guide covers the rule in full.
Planning permission and conservation areas
On a new build the roof, PV included, is assessed as part of the planning application for the house, so there is no separate solar consent. Context changes what planners will accept:
- Conservation areas: planners may resist panel arrays on prominent roof slopes and prefer tiles or slates that match neighbouring roofs.
- Article 4 directions: check what the local direction covers; it can remove permitted development rights that would otherwise apply after the house is built.
- Listed-curtilage plots: the effect on the setting of the listed building will be weighed; matching slate or tile products are more likely to be accepted than panels.
- National Landscapes: appearance carries more weight, so expect similar scrutiny to conservation areas.
In a conservation area the planning question is how visible the array is and how closely it matches the roof covering. The solar roof tiles guide compares tile and slate systems on appearance and cost.
Installing a BIPV solar roof: what to check
- MCS certification for the specific product and the installer. Homeowners need the MCS certificate to claim Smart Export Guarantee payments.
- One programme for roofer and electrician. Tiles and slates are laid by or alongside the roofer; the electrical work and commissioning follow. Agree who is responsible for the weathering details at the array edges.
- Grid notification. Systems up to 16 A per phase (3.68 kW on a single phase) are notified to the network operator under G98 after commissioning; larger systems need G99 approval first.
- Warranty provider requirements. Check what your structural warranty provider needs to see for a roof-integrated system before the roof design is fixed.
- Spares. Ask for spare tiles or slates of the same batch, so a damaged unit can be matched later.
Which to choose
For new builds outside heritage-sensitive areas, in-roof panels are the sensible default: lower cost per kWp, more output from the same roof, and the same standing under Part L 2026. For conservation areas, Article 4 zones, National Landscapes and listed-curtilage plots, a BIPV solar roof of tiles or slates is often what planners will accept. For premium custom builds where the architect specifies BIPV for its appearance, the premium is small relative to the build budget.