How Solar Panels Are Installed: Step by Step (2026)

The part of solar nobody shows you

If you have spent any time researching solar, you will have seen a hundred pages comparing panel brands and almost none explaining what actually happens when a crew arrives at your house. That gap matters. The panels fitted in Leeds are the same panels fitted in Plymouth — what separates a good installation from a bad one is the work: where the anchors land, how the strings are designed, where the inverter goes, and whether the paperwork arrives afterwards.

This guide walks through a professional UK domestic installation from scaffold to handover, so you know what good looks like before anyone touches your roof. If you are still at the pricing stage, start with what installation actually costs in 2026 and our cost guide, then come back here.

Before anyone climbs a ladder

A properly-run installation is mostly decided before installation day. Three things should already have happened.

A real survey. Someone should have been in your loft checking rafter size, spacing and condition, and at your consumer unit checking spare ways and the earthing arrangement. A quote produced from Google Earth without either check is guesswork, and it is where “surprise extras” on the day come from. An on-roof array adds roughly 15–20 kg per square metre; most post-war trussed roofs carry that comfortably, but the survey is what confirms yours does.

The grid paperwork, in the right order. Systems up to 16 A per phase — about 3.68 kW of inverter output — can be connected and then notified to your Distribution Network Operator within 28 days under G98. Anything larger, which includes most solar-plus-battery systems, needs a G99 application approved before the system is energised. The Energy Networks Association connection guidance explains both routes and helps you find your DNO. We cover the boundary in detail in G98 vs G99 explained — the short version is that on a G99-scale job, an installer who says “we’ll sort the paperwork after fitting” is proposing to do it in the wrong order.

Scaffold booked and coordinated. Roof work from ladders is indefensible for a crew installing panels — the HSE’s work-at-height guidance is why scaffolding appears on almost every quote, typically at £600–£1,200. The scaffold usually goes up a day or two before the crew arrives. If your installer subcontracts it (most do), ask who owns the coordination, because scaffold arriving a fortnight before or after the install crew is one of the most common complaints in this industry.

Step 1: Setting out the array

On the morning of the install, the roof crew measures and marks the array position against the design drawing — not by eye. Setting out fixes the array’s position relative to the roof edges and, critically, locates the rafters. On a tiled roof the crew finds rafters by lifting tiles and sighting the timber line; positions are then marked so every anchor lands in structural timber.

This is also the moment string design earns its keep. A string is a run of panels wired in series into one inverter input. If a chimney shades three panels for two hours each morning, those panels belong on their own string — or on optimisers — so they do not drag down the whole array. Shading strategy decided at the design stage does far more for real-world yield than the badge on the panel.

Step 2: Roof anchors — the quality tell

Roof anchors (also called roof hooks) are the single most important components on the job, and the ones you will never see again once the panels go on.

On a concrete or clay tile roof, the crew lifts a tile, screws the anchor through the membrane zone into the rafter with structural coach screws, then dresses the tile back over the anchor — grinding or working the tile around the bracket so it sits flat and sheds water. On slate, the detail changes: slate is brittle, so slate-specific hooks or careful dressing are needed, and a crew that has mostly done concrete tile can crack a lot of slate learning.

What must never happen: anchors screwed into thin air or batten only, anchors bedded on felt, or brackets foam-glued to the roof covering. Every one of those fails slowly — the leak arrives the following winter, long after the invoice was paid.

The single best piece of advice in this guide: ask for fixing photos. A good crew photographs each anchor landed in its rafter before the rails and panels cover the evidence, and the photo set goes in your handover pack. If an installer cannot show you fixing photos from previous jobs, that tells you something about how they fix.

Step 3: Rails and bonding

Aluminium mounting rails bolt to the anchors and are levelled and aligned across the roof face. The crew torques the connections to the manufacturer’s specification — rail systems are engineered products with wind-load calculations behind them, not generic metalwork. Where required by the earthing design, the rails and panel frames are bonded so the whole array sits at the same potential.

Rail time is also when bird-proofing should be discussed if your street has a pigeon population. Mesh fitted now, clipped to the panel frames, costs a fraction of a retrofit visit that needs the scaffold back up.

Step 4: Panels and DC cabling

Panels are carried up, laid onto the rails and clamped — mid-clamps between panels, end-clamps at the row ends, all torqued rather than gunned tight. As each panel lands, the crew connects its leads to the next panel in the string using the MC4-style connectors, and the string cabling is clipped and routed so it cannot chafe on tiles or dangle onto the membrane. Sagging DC cable that touches the roof surface is a small detail that separates tidy crews from careless ones; it abrades over 25 years of wind movement.

The DC runs then come off the roof — usually through a weathered entry or alongside a soil stack — and travel to the inverter position. DC cabling at several hundred volts deserves respect: it is run in its own containment, clearly labelled, with a DC isolator near the inverter so the array can be safely disconnected.

Step 5: The inverter, and where it should go

The inverter converts the array’s DC output to 230 V AC and works hard every daylight hour for its 10–12 year typical life. Heat is what kills inverters, which is why siting matters: a cool, ventilated garage, utility room or plant cupboard beats a baking loft. Lofts are the easy cable run, not the right answer — UK loft temperatures in summer shorten electronics’ lives, and if a battery is involved the siting question becomes a safety standard, not a preference. PAS 63100:2024 steers domestic batteries away from lofts, escape routes and bedrooms entirely — we cover it fully in where a home battery should go.

The electrician mounts the inverter, fits the AC and DC isolators, connects into your consumer unit (with surge protection where the design calls for it), and installs the generation meter and any consumer-unit alterations that were — or should have been — identified at survey.

Step 6: Commissioning — the tests that prove the job

Commissioning is not “switch it on and see”. Working to BS 7671 and the IET Code of Practice for grid-connected solar, the electrician should:

• Test insulation resistance on each DC string, proving the cabling has no damage or moisture ingress
• Verify polarity and string voltages — open-circuit voltage per string checked against the design figures, which catches miswired strings immediately
• Confirm earth continuity and bonding across the array and containment
• Configure the inverter for the correct grid code (G98/G99 settings) and check it connects, synchronises and exports as designed
• Record everything on a test schedule that forms part of your Electrical Installation Certificate

Then the walkthrough: the monitoring app set up on your phone, an explanation of what normal generation looks like for the season, and where the isolators are if you ever need to shut the system down. You should end the day with the system generating and a clear statement of what paperwork follows.

What the crew should leave behind

The physical install is half the product. The other half is documentation, and each item has a job:

1. The MCS certificate — registered within about 10 working days of commissioning. This is the gateway to Smart Export Guarantee payments; you can verify any installer on the MCS certification scheme site before you sign. No certificate, no export income.
2. The Electrical Installation Certificate under BS 7671, with the test results schedule attached.
3. DNO evidence — the G98 notification confirmation or the G99 approval, depending on system size.
4. Warranty registrations — panels typically 25 years performance, inverter typically 10–12 years.
5. The insurance-backed workmanship warranty, which steps in if the installing firm ever ceases trading.

Plus the extras a proud crew includes: the fixing photo set, an as-built layout drawing showing string arrangement, and the monitoring login. Missing paperwork is not a technicality — conveyancers increasingly ask for the full set at house sale, and chasing it years later from a firm that has changed hands is miserable.

How long the whole thing takes

The on-roof work for a typical 8–14 panel domestic system is one to two days: scaffold up beforehand, mounting and panels day one, electrical completion and commissioning finishing day one or two. The full journey from accepted quote to switch-on is typically four to eight weeks, driven by scaffold scheduling, kit lead times and — on battery or larger systems — DNO approval timescales. The details differ by roof construction; our pitched-roof installation guide covers the standard UK tile and slate install in more depth.

Questions people ask about installation day

Do I need to be home during the installation? For the roof work, no — but the electrician needs access to your consumer unit, loft and the inverter location, and the commissioning walkthrough is genuinely worth being present for. Most installers ask for someone home on the final afternoon. If the crew finishes and nobody has shown you the isolators and the app, that walkthrough was skipped, not unnecessary.

Will the installers damage my tiles? Some tile lifting and occasional breakage is normal on older roofs, and a professional crew carries spares or reuses sound tiles from the array footprint. What is not normal is cracked tiles walked in across the roof and left. Ask before the job how breakages are handled, and ask specifically about slate experience if you have a slate roof — the fixing detail and the breakage risk are both different.

What happens if it rains on installation day? Light rain slows a crew; heavy rain or high wind stops roof work, because working-at-height rules and common sense both say so. A crew that pushes on through a gale is not one you want fixing anchors. The membrane under your tiles keeps the roof weathertight while tiles are lifted, so a paused job is an inconvenience rather than a risk.

Ready to compare quotes properly? Request a free quote — or if you want the numbers first, our cost guide and FAQs cover what a properly-itemised 2026 quote should contain.