Pitched-Roof Solar Installation

The standard UK solar install — and who it suits

If you own a house with a tiled or slated pitched roof — which describes most UK homeowners looking at solar — this is the installation type nearly every quote you receive will be describing. Panels clamped to aluminium rails above the tiles, fixed through the tile line into the rafters, wired down to an inverter: the on-roof method is the default for concrete tile, clay tile and slate, and MCS-reported installation data puts the England average price at roughly £1,565–£1,590 per kW as at spring 2026.

A typical domestic system is 3.5–6 kWp — eight to fourteen panels of 440–475 W each, occupying 18–32 m² of roof — generating 3,000–5,500 kWh a year depending on size, orientation and shading. Fully installed, most homes land between £5,500 and £9,500, with payback around eight years at current electricity prices.

This page explains how the job is actually done, because the installation is where that money either becomes a 25-year asset or a source of winter leaks. The panels are broadly commodity items now. What separates a good installation from a bad one is almost entirely the work: where the anchors land, how the strings are designed, where the inverter lives, and whether the paperwork arrives.

How a pitched-roof installation is actually done

Two trades deliver a pitched-roof install: a roof crew and an electrician, usually working in parallel across one to two days once the scaffold is up. Here is the sequence a properly-run job follows.

Before anyone climbs a ladder

The real work starts at survey. Someone should physically get into your loft to check rafter size, spacing and condition — an on-roof array adds roughly 15–20 kg/m², which most post-war trussed roofs carry comfortably, but “most” is not “all”. The surveyor should also open your consumer unit to check spare ways and the earthing arrangement, map shading from chimneys, dormers and neighbouring trees, and confirm the planning position in writing. A quote produced from Google Earth without a loft or fuse-board inspection is guesswork, and the gap tends to surface as “extras” on installation day.

Scaffold goes up first

Scaffolding to the working eave is a legal working-at-height requirement on almost every pitched-roof job — roof work from ladders is indefensible for a crew handling panels. It is typically £600–£1,200 of a domestic quote, erected a day or two ahead of the install crew by a separate scaffolding firm. Coordination matters here: scaffold arriving weeks adrift of the install crew is one of the most common complaints about badly-run projects, so ask who owns that scheduling.

Day one: fixings, rails, panels

The roof crew sets out the array positions, then fixes the mounting. On a tiled roof this means lifting tiles along the fixing lines and screwing roof hooks (anchors) through into the rafters — structural timber, never just the felt or battens. The lifted tile is then ground or worked around the hook so it sits back flush; a tile left riding proud of a hook will crack under foot traffic or wind load. On natural slate the detail changes to slate-specific hooks or careful dressing, and it is fair to ask how many slate roofs the crew has actually done, because a concrete-tile crew can crack a lot of slate while learning.

Fixings are the single biggest quality tell of the whole job. Anchors bedded on felt, glued with foam, or screwed into thin air between rafters are the failures that produce leaks the following winter — often after the installer has stopped answering the phone. A confident installer photographs every fixing before the panels cover it and puts the photo set in your handover pack. If a firm cannot show you fixing photos from previous jobs, that silence is informative.

With hooks in, the crew bolts aluminium rails across them, checks alignment and torque, and lands the panels, clamping each one and connecting the pre-fitted plug-and-socket DC connectors panel to panel as they go.

The electrical side runs in parallel

While the roof crew works, the electrician routes the DC cabling from the array down to the inverter position — ideally a cool, ventilated space such as a garage or utility area rather than a baking loft, because inverters derate and age faster in heat. They mount the inverter, fit DC and AC isolators, add surge protection where the design calls for it, and connect into the consumer unit. String design matters more than panel brand here: how the panels are grouped into strings around chimneys, dormers and shading patterns decides real-world yield, and optimisers or micro-inverters belong on the quote only where shading genuinely justifies them, not as a default upsell.

Commissioning and sign-off

Commissioning closes the job: insulation-resistance and polarity tests on the DC side, inverter configuration, a check of the generation metering, and a walkthrough of the monitoring app so you know what normal output looks like. You should end the final day with the system generating and a clear written list of the paperwork that follows — MCS certificate, Electrical Installation Certificate, DNO notification evidence and warranty registrations.

What corner-cutting looks like

The pattern of a rushed job is consistent: no loft inspection at survey, anchors foam-glued or bedded on felt, cracked tiles walked in and left, the inverter hung in the hottest corner of the loft because the cable run was short, no fixing photos, and DNO paperwork “to follow” indefinitely. Every one of those is checkable, which is precisely why this page describes the method in detail.

Sizing and cost in 2026

Sizing starts from your consumption, not your roof area. A home using 3,500–4,500 kWh a year with some daytime occupancy is usually well served by 3.5–5 kWp; add an EV or a heat pump and 6–8 kWp with storage starts to justify itself. With 440–475 W panels now mainstream, the old “12 panels for 3 kW” rule of thumb overshoots — fewer, bigger panels cover most homes, which is why 8–14 panels is the typical count.

On price, the MCS-reported England average of roughly £1,565–£1,590 per kW as at spring 2026 gives you a sanity check on any quote: a typical 3.5 kWp installation lands around £5,500–£8,000 fully installed, and 5–6 kWp roughly £7,500–£9,500 and up. Quotes a long way either side of the per-kW average deserve an itemised explanation — the usual suspects are scaffolding (in or out), inverter class (budget string versus hybrid battery-ready), whether the DNO and MCS paperwork is handled for you, and whether the survey was real. Domestic installations currently attract 0% VAT, a genuine dated saving that runs until 31 March 2027 before reverting to 5%. The full price breakdown by system size is on our cost guide, and the export and VAT positions are covered under grants and funding routes.

Self-consumption drives the payback more than headline yield: a unit you use on site is worth your import price (around 26p), while an exported unit earns your Smart Export Guarantee rate — roughly 12–16p/kWh on leading tariffs as at mid-2026, always worth re-checking before you sign. That gap is why array orientation splits and battery pairing are sizing decisions rather than extras; if storage is on your list, the solar battery installation page covers the siting and paperwork implications properly.

Planning rules and the paperwork trail

For most houses in England, rooftop solar is permitted development under GPDO Part 14 Class A — no planning application needed. The rules were rewritten by SI 2026/896 with effect from 27 August 2026: roof-slope panels keep their 0.2 m projection limit, while wall-mounted panels on a house may now project up to 0.4 m (0.2 m where the wall fronts a highway). The exceptions that still catch people are listed buildings (always need consent), certain conservation-area elevations, and some flat configurations. Note the England-only caveat: the GPDO is English legislation, and Scotland and Wales run their own regimes. A proper installer confirms the planning position in writing at survey rather than leaving you to assume.

The electrical side is notifiable work under Building Regulations Part P, executed to BS 7671 with an Electrical Installation Certificate at handover. Grid connection runs through your District Network Operator — the company that owns the wires, not your supplier. Up to 16 A per phase (about 3.68 kW of inverter output) the installer connects and then notifies within 28 days under G98. Above that — which includes most solar-plus-battery combinations — a G99 application must be approved before the system is energised, and the DNO can impose export limits. An installer who says they will “sort the paperwork after fitting” on a G99-scale system is describing the wrong order of operations, and it can end with an inverter forced to run export-limited.

A worked scenario: 4.4 kWp on a 1930s semi

A scenario, not a client case study — the numbers are modelled from the ranges above. Take a 1930s semi with a south-east/south-west roof split: 10 × 440 W panels across the two faces (4.4 kWp), a hybrid inverter, and a 9.5 kWh battery sited in the garage in line with PAS 63100. Because the battery tips the system past G98 limits, the G99 application goes in at survey stage and comes back approved before installation. Scaffold up on day zero; panels, electrics and commissioning complete across two days; fixing photos in the handover pack.

PVGIS modelling for the split orientation puts annual generation around 3,900 kWh. With the battery, modelled self-consumption is roughly 78% versus about 42% without — and that difference, combined with off-peak overnight charging on a smart tariff and SEG export at current dated rates, produces an annual benefit in the £1,050–£1,250 range and a payback around 8.5 years. The same roof without storage models closer to an 11-year payback. The point of the scenario is that the design decisions — orientation split, string layout, battery siting, paperwork order — move the outcome more than any panel brand choice.

Pitched-roof installation questions

How long does a pitched-roof installation take?

One to two days on the roof for a typical domestic system: scaffold up beforehand, mounting and panels on day one, electrical connection 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 — for battery or larger systems — DNO approval.

How are the panels actually fixed to my roof?

Through it, not to it. Roof hooks are screwed into the rafters beneath the tile line, tiles are worked around the hooks so they sit flush, and the panels clamp to rails bolted across the hooks. Nothing should rely on adhesive, felt or battens. Ask to see fixing photographs — a good installer takes them on every job before the panels go on.

Will the installers damage my tiles?

Some tile lifting is inherent to the method, and a competent crew works around fragile tiles and replaces any casualties as part of the job. Natural slate and older clay tiles need more care than concrete — breakage handling should be agreed in the quote, not negotiated on the day. Cracked tiles walked in and left is a corner-cutting tell.

Do I need planning permission for panels on a pitched roof?

For most houses in England, no — it is permitted development under Part 14 Class A, and the roof-slope projection limit stays 0.2 m, and from 27 August 2026 wall-mounted panels on houses gained a 0.4 m allowance (SI 2026/896). Listed buildings always need consent, some conservation-area elevations are restricted, and Scotland and Wales have their own rules. Get the planning position in writing at survey.

What paperwork should I have at the end?

Five documents: the MCS certificate (within about 10 working days — it unlocks Smart Export Guarantee registration), the Electrical Installation Certificate, DNO notification or G99 approval evidence, manufacturer warranty registrations (panels typically 25 years performance, inverter 10–12), and the insurance-backed workmanship warranty. Missing paperwork surfaces at house sale — conveyancers increasingly ask for the set.

Where to go next

If your roof is coming off anyway, or a conservation officer objects to panels above the tile line, an in-roof solar installation sits flush in the roofline and is at its cheapest at re-roof time. Pairing the array with storage changes the paperwork and siting rules — the solar battery installation page explains PAS 63100 siting and the G99 sequence. For numbers, see typical costs and payback, check what funding applies, or request a quote and have the survey done properly.