A roofing crew that lays clay and concrete tiles every week still slows down the first time a crate of solar roof tiles arrives. The lap looks familiar. The difference is that every unit carries a junction box, two leads and a fixed place in an electrical string.
This guide follows solar roof tile installation in the order it happens on site, from delivery to single-unit replacement. It covers sequence and interfaces; fixing torques, load values, minimum pitch and batten gauge come from the installation drawing supplied with the order.
Solar roof tiles are installed like an interlocking tile roof with a wiring layer underneath. Underlay and mounting rails or battens go on first. Tiles are laid in courses from the eaves up to the ridge, each course lapping over the one below, and plugged into series strings through MC4 connectors as they go. Standard flashing closes the edges, and each string is tested for open-circuit voltage and insulation resistance before it is connected.
Interlocking solar roof tile installation: individual glass PV tiles hook onto mounting rails or battens, interlock with their neighbours and lap over the course below. The tiles replace the roof covering unit for unit. This is the method this guide covers.
Solar shingle strip installation: long, flat PV strips are fixed through a roof deck and underlayment in overlapping courses, the way asphalt shingles are laid.
In-roof tray installation: standard-size PV modules sit inside a flashing tray or frame that forms the watertight layer, with conventional tiles laid around the tray.
Rack-mounted installation: standard modules are clamped to rails on hooks or brackets above a complete roof covering, which still does the waterproofing. Hardware for that route is in our solar panel bracket range.
Quick facts: the tiles this guide is based on
| Item | 650 mm format | 1208 mm format |
|---|---|---|
| Size (mm) | 650 × 432 × 22 | 1208 × 432 × 22 |
| Weight | 5.5 kg | 10 kg |
| Pmax (STC) | 43 W | 85 W |
| Voc / Vmp | 8.2 V / 7.0 V | 16.4 V / 14.0 V |
| Isc / Imp | 6.32 A / 6.08 A | 6.32 A / 6.08 A |
| Voc temperature coefficient | -0.36 %/°C | |
| Max system voltage / max series fuse | 1000 V / 15 A | |
| Connector / junction box | MC4 on 45 cm leads / IP67 | |
| Build | 3.2 mm + 3.2 mm double glass, 182 mm monocrystalline cells | |
| Packing | Wooden crate; tiles per crate (confirmed with the quote) | |
What is solar roof tile installation?
Solar roof tile installation is the process of fixing photovoltaic tiles to a pitched roof so that they form the weatherproof roof covering and a wired PV array at the same time. The roof covering and the generator go on in one pass, by one crew.
Solar roof tiles are a building-integrated photovoltaic (BIPV) product, the category studied by the IEA PVPS Task 15 research programme on BIPV. A BIPV roof product is judged twice: once as roofing, once as an electrical device.
Two trades share the work. The roofing contractor owns the underlay, rails or battens, laps, flashing and fixings. The electrician owns the string design, connector quality, DC protection, testing and the connection to the inverter.
Sequence matters more than on a plain tile roof. Every tile laid is also an electrical joint that the next course will hide, so a fault found after the ridge is closed means lifting finished roof.
What arrives on site for a solar roof tile job
A solar roof tile delivery arrives as glass-glass PV tiles packed in wooden crates, in two crystalline formats: 650 × 432 × 22 mm weighing 5.5 kg, and 1208 × 432 × 22 mm weighing 10 kg. Both formats share the same electrical current, so one roof can use both.
Each tile is a laminate of 3.2 mm glass on both faces around 182 mm monocrystalline cells. On the back sits an IP67 junction box with two MC4 leads, each 45 cm long.
The weight per square metre of tile, calculated from datasheet values, is 10 kg ÷ (1.208 m × 0.432 m = 0.522 m²) = 19.2 kg/m² for the long format, and 5.5 kg ÷ (0.650 m × 0.432 m = 0.281 m²) = 19.6 kg/m² for the short one.
Those figures cover the tile only. Rails, battens, underlay and flashing add to the dead load, and the structural check for the roof stays with the project engineer.
The short 43 W format exists for positions where a full-length tile will not fit. Typical spots are the end of a course at a verge, or the space beside a dormer or roof window.
Checks when the crates are opened:
- Count tiles by format against the delivery note and the roof layout.
- Look at every glass edge and corner for chips before the tile goes to the roof.
- Check that each junction box lid is closed and both leads and connector caps are intact.
- Keep crate labels; batch information matters if a colour-matched spare is needed later.
Carry tiles by the glass edges, never by the leads or junction box. Whether a laid tile can be walked on, and where, is stated on the installation drawing supplied with the order; until you have it, use crawl boards.
How to prepare the roof for solar roof tiles
Roof preparation for solar roof tiles means a sound structure, a continuous underlay and the mounting rails or battens set out to the tile drawing before any glass goes on. The tiles are the first water-shedding layer, and the underlay is the second line of defence, the same as on a conventional tile roof.
Underlay. Lay the underlay the tile drawing and the local roofing code call for, lapped and dressed into the gutter at the eaves. Cables will run above it, so any hole or tear left now sits under a live array later.
Rails or battens. In the installation example photographed further down, the tiles hang on slotted galvanised steel rails running across the slope, with black clip blocks holding the tile edges. How those rails fix to the roof, onto battens, counter-battens or rafters, is per the installation drawing supplied with the order.
Batten gauge. Set the batten or rail gauge per the tile drawing. The 432 mm tile height is the unit size, and the spacing between rails depends on the lap, which the drawing fixes. Do not derive the gauge from the unit size alone.
Set out in whole tiles. A glass PV tile cannot be cut to length like a clay tile, because cutting would break the laminate and the cell circuit. Measure the roof slope from eaves to ridge and from verge to verge, and plan the PV field as a block of whole tiles, using the 650 mm format to close courses.
Draw the string map first. Before the first tile goes down, the electrician marks which tile belongs to which string and where the home-run cables pass through the underlay. Fit a sealed cable entry there now, while the area is open, and mark the string plan on the rails so the roofer plugs to it.
The solar roof tile laying sequence, from eaves to ridge
Solar roof tiles are laid in horizontal courses starting at the eaves and working up to the ridge, so each new course laps over the head of the course below and sheds water onto it. Each tile is plugged into its string as it is laid, while the connection is still visible.
- Fit the eaves detail. Install the eaves flashing or closure piece shown on the drawing, with the underlay dressed over it into the gutter.
- Fix the first rail. Set the eaves rail or batten at the position the drawing gives for the first course.
- Lay the first course. Start at the verge the drawing indicates and work across. Hook each tile onto its rail and engage the side interlock with its neighbour. The edge profile sets the direction, so every tile in the course faces the same way.
- Plug as you lay. Mate the new tile's MC4 lead to the previous tile's opposite-polarity lead. Push until it clicks, then give it a firm pull to confirm the lock.
- Clip the leads. Secure the leads and connectors to the rail so they do not hang loose, rest on the underlay where water runs or sit against a glass edge.
- Test the course. With a multimeter, read the open-circuit voltage across the part-string laid so far. It should be close to the number of tiles times the tile Voc, corrected for tile temperature. A zero reading means an open joint; fix it now.
- Lay the next course. Lap it over the head of the course below by the overlap on the drawing, in staggered or straight bond as specified.
- Change course with a jumper. Where a string runs from one course to the next, use the extension lead the string map specifies, with the same connector type as the tiles.
- Finish at the ridge. The top course must be whole tiles; the remaining gap up to the ridge is closed with ridge flashing or conventional covering.
- Label and test the string. Tag both home-run ends with the string number and polarity, then run the commissioning tests before anything connects to the inverter.
Staggered bond offsets the side joints of each course from the course below. Straight bond lines them up. The tile drawing states which bond a product is designed for, and the choice also changes how strings run from course to course.
How solar roof tiles meet eaves, verges, ridge, valleys and penetrations
Solar roof tiles meet the rest of the roof at five kinds of interface (eaves, verges, ridge, valleys or hips, and penetrations), and each is closed with standard flashing or conventional roof covering, with no PV tile cut to fit. A PV field laid as a block of whole tiles keeps these details routine for a roofer.
| Interface | What happens there | What handles it | Check before covering |
|---|---|---|---|
| Eaves | First course; water leaves the roof | Eaves flashing or closure, underlay dressed into the gutter | First rail position per drawing; no cable in the drip line |
| Verge | Side edge of the PV field | 650 mm tile to close the course, then verge flashing or conventional verge | Side lap fully engaged; string end reachable |
| Ridge | Top of the field | Ridge flashing or ridge tiles over a whole-tile top course | Ridge ventilation per roof design |
| Valley or hip | Diagonal line across courses | PV field stops short; conventional tiles cut to the valley or hip, flashed to the field | No PV tile cut or overhanging the valley gutter |
| Penetrations | Vents, flues, roof windows, cable entries | Kept outside the PV field where possible; standard flashing kit in conventional covering | Cable entry sealed to the underlay |
| Field to conventional covering | Head or side of the PV block | Head and side flashing per drawing | Laps run the same direction as the tiles |
The tiles use a low-pitch waterproof overlap design, as stated by the supplier. The minimum roof pitch for a given product and roof build-up is confirmed per project on the installation drawing, not assumed from that description.
Settle flashing supply before the job is priced: ask whether the flashings come with the tiles or are sourced locally to the drawing.
How solar roof tiles are wired into series strings
Solar roof tiles are wired in series strings: the positive MC4 lead of one tile plugs into the negative lead of the next, and each string's two free ends run as home-run cables to the inverter input or a combiner. The voltages add along the string while the current stays the same.
The datasheet values that drive string design are Voc 8.2 V (43 W) and 16.4 V (85 W), Vmp 7.0 V and 14.0 V, Imp 6.08 A and Isc 6.32 A for both formats, a maximum system voltage of 1000 V and a maximum series fuse rating of 15 A.
Open-circuit voltage rises in cold weather. The Voc temperature coefficient is -0.36 %/°C, so the string voltage on the coldest morning sets the limit. The design temperature is project-specific: the lowest expected ambient for the site, taken from local code or climate data.
String length formula
Voc,max per tile = Voc,STC × [1 + (-0.36 / 100) × (Tmin - 25 °C)]
Maximum tiles per string = floor( Vlimit ÷ Voc,max per tile ), where Vlimit is the lower of 1000 V and the inverter's maximum DC input voltage.
Worked example, calculated from datasheet values, with an assumed design temperature of -10 °C: correction factor = 1 + (-0.0036 × -35) = 1.126. For the 85 W tile, 16.4 V × 1.126 = 18.47 V, and 1000 ÷ 18.47 = 54.1, so 54 tiles. For the 43 W tile, 8.2 V × 1.126 = 9.23 V, and 1000 ÷ 9.23 = 108.3, so 108 tiles.
A string that mixes formats is checked the same way: (number of 85 W tiles × 18.47 V) + (number of 43 W tiles × 9.23 V) must stay at or below Vlimit.
In practice the inverter's input window usually decides string length before the 1000 V limit does. For example, a string of 20 of the 85 W tiles (a length assumed for illustration) has an operating voltage of 20 × 14.0 V = 280 V and a rated power of 20 × 85 W = 1,700 W (calculated from datasheet values), which the electrician checks against the inverter's MPPT range at both hot and cold conditions.
Parallel strings and fusing. Where strings are paralleled on one input, any string fuse must not exceed the 15 A maximum series fuse rating. Whether fuses are needed at all depends on the number of parallel strings and local electrical rules.
Connection count. A string of N tiles has N - 1 tile-to-tile MC4 joints under the roof. One kilowatt of the 85 W format is 12 tiles (1000 ÷ 85 = 11.8, rounded up), so a 54-tile string hides 53 joints. Every one is a potential open circuit or leak path for current, so mate only connectors of the type specified for the tiles.
Lead reach. Each tile has two 45 cm leads. Check on the tile drawing where the junction box sits and whether the leads reach the neighbouring tile's leads directly; if they do not, the string map should show extension leads of the same connector type.
Cable routing. Run leads and jumpers along the rails, clipped at intervals, clear of sharp rail edges and off the underlay where water runs. Take home runs through the sealed underlay entry fitted during preparation.
The IP67 junction box is dust-tight and protected against temporary immersion; connectors still belong off the underlay water path.
Bonding. The installation example shows yellow-green bonding leads between rail sections. Whether the metal rail system needs equipotential bonding, and how it is terminated, follows local electrical code and the installation drawing.
Commissioning checks for a solar roof tile system
Commissioning a solar roof tile system means proving that each string is wired, insulated and producing correctly before it is connected, with polarity, open-circuit voltage, current and insulation resistance recorded string by string. IEC 62446-1 sets out the commissioning tests, inspection and documentation expected for grid-connected PV systems.
Polarity. Confirm at the tagged home-run ends that positive and negative are where the labels say. A reversed pair at the inverter is the cheapest fault to catch here and one of the most expensive to catch later.
String open-circuit voltage. Measure each string's Voc and compare it with the expected value: tiles in the string times 16.4 V (or 8.2 V for short tiles), adjusted for tile temperature at the time of the test.
A reading of zero points to an open connector. A reading short by one tile's Voc, or a multiple of it, points to a tile that was skipped or is not contributing. Equal strings measured in the same light should read close to each other.
Current. Check the short-circuit or operating current per string with suitable test equipment, scaled against the 6.32 A Isc for the irradiance at the time of the test.
Insulation resistance. Test between each string pole and earth at the test voltage the standard gives for the system voltage. A lead nicked by a rail edge during laying shows up here, while the location is still recorded on the string map.
Visual inspection. Walk the field from the crawl boards: every tile seated and interlocked, no cracked glass, all flashing complete and no cable visible at the laps.
Electroluminescence (EL). Pre-shipment EL images reveal cell cracks that a visual check cannot. Ask the supplier for pre-shipment EL and flash test data for the batch; both are available on request.
Handover record. Keep the string map, each string's readings with test date and conditions, and photos of the wiring taken before each area was covered.
How to replace a single solar roof tile
A single solar roof tile is replaced by isolating its string, lifting or releasing the tiles that lap over it, unplugging its two MC4 leads and fitting a new unit of the same format. Because each tile is its own unit, the rest of the roof stays in place.
- Isolate the string. Switch the inverter off and open the DC isolator so no current flows. The tiles still produce voltage in daylight, so never separate an MC4 joint under load.
- Find the tile. Locate it on the string map; the handover photos show where its leads run.
- Release the course above. Lift or unclip the overlapping tiles by the method on the installation drawing.
- Unplug and unhook. Separate the two MC4 joints with the proper unlocking tool, then unhook the tile from its rail.
- Fit the replacement. Hook in a tile of the same format and colour, plug both leads, pull-test the joints and clip the leads.
- Relay and retest. Refit the overlapping tiles, then re-measure the string Voc and insulation resistance before reconnecting.
Colour matching decides how clean a repair looks. The tiles come in custom colours, so order a few spare units of each format with the main order, from the same batch, and store them with the handover file.
What to ask the supplier before the first solar roof tile job
Before the first solar roof tile job, a contractor should get the installation drawing, string design limits, interface details and commercial terms in writing from the supplier. Everything this guide marks "per the installation drawing" belongs on that list.
- Installation drawing: rail or batten gauge, fixing method and spacing, lap dimension, side interlock direction, bond type and minimum roof pitch.
- Interface details: eaves, verge, ridge, valley and penetration flashings, and who supplies each piece.
- Access: whether laid tiles can be walked on, and where.
- Wiring: junction box position, lead reach to the neighbouring tile, extension leads for course changes and the connector type to mate with.
- Datasheet: Voc, Vmp, Isc, Imp, temperature coefficients, maximum system voltage and maximum series fuse for each format.
- Test reports: the crystalline tiles we supply are tested to IEC 61215:2021 / IEC 61730:2016, test reports available on request.
- Quality data: pre-shipment EL and flash test data per batch, available on request.
- Packing: tiles per crate confirmed with the quote.
- Commercial terms: MOQ, lead time, unit price and warranty terms are set out in the project quote.
- Sample: a paid sample, quoted on request, to build a small mock-up of the lap before the production order.
A mock-up of a few courses with real flashing is the fastest way for a roofer to sign off a lap detail they have not laid before. Formats, specifications and sample requests are on our solar roof tiles supply page.
If the project keeps its existing roof covering and adds PV on top, compare the rack-mounted route in our guide to solar panel racking systems. For a tile project, contact us with the roof drawing, site location and preferred inverter, and we will reply with the datasheet and a quotation.
Solar roof tile installation FAQ
Solar roof tile installation questions from contractors mostly cover whether the tiles work, cost, downsides, cutting and who does the wiring.
Do solar roof tiles work as a real roof and a real PV system?
Solar roof tiles work as both roof covering and generator when they are laid to the installation drawing and wired to a proper string design. The 85 W tile is rated at 85 W at standard test conditions, and the lapped courses shed water like a conventional tile roof.
How much does a solar tile roof cost to install?
The cost of a solar tile roof depends on roof area, the mix of 650 mm and 1208 mm formats, the flashing work at the interfaces and the electrical design, so it is quoted per project. LinkSolar quotes the tile supply from the roof drawing; installation labour is priced by the contractor.
What are the downsides of installing solar roof tiles instead of panels on a roof?
The main installation downside of solar roof tiles is the number of electrical connections: 12 of the 85 W tiles per kilowatt, each with its own junction box and MC4 joint, against a handful of large modules. That means more plugging time and more joints to test.
Can a solar roof tile be cut to fit a valley or verge?
A solar roof tile cannot be cut, because it is a glass laminate with a live cell circuit inside. Valleys, hips and odd-shaped edges are finished in conventional roof covering with flashing, and the 650 mm format closes courses where a full tile will not fit.
Can a roofer install solar roof tiles without an electrician?
A roofer can lay and plug solar roof tiles to a string map, but string design, DC protection, testing and grid connection need a qualified electrician under local rules. For US projects, the U.S. Department of Energy homeowner's guide to going solar outlines the permitting and utility interconnection steps.