Solar Panels for Garages: The Roof Everyone Forgets
Garage roofs are 10–15% cheaper to panel than house roofs, with the same planning rights. But flat roofs hide a one-tonne catch — here’s the honest guide.
The short answer
Yes — garage roofs are genuinely good solar real estate, and oddly overlooked. They carry the same permitted development rights as house roofs, installs run 10–15% cheaper (low roofs often need no scaffolding), and a south-facing garage earns the same per panel as a south-facing house. A single garage fits 4–6 panels (~1.8–2.7kW), a double fits 8–10 (~3.5–4.5kW). The smart money move: add garage panels to a house install, where the marginal cost per panel is small — a standalone garage system needs about six panels minimum to pay its way (from ~£4,000–£5,500).
The honest catches: flat roofs need ballasted mounting — roughly 80kg of ballast per panel, about a tonne for ten — which many prefab concrete and single-skin garages simply can’t carry; corrugated asbestos garage roofs shouldn’t be drilled at all; and no, a couple of panels won’t run a garage heater in winter. Structure first, then panels.
What this guide covers
Installers quote house roofs all day while a perfectly good south-facing garage sits ignored ten feet away. Sometimes the garage is the better roof — unshaded, ideally angled, cheap to work on. Sometimes it’s a prefab box that would buckle under a ballasted array. This guide is about telling the difference before anyone’s money moves.
Planning rights — and why garage installs cost less
Garages and outbuildings within your property’s curtilage enjoy the same permitted development rights as your house roof: no planning application for the vast majority of homes (the exceptions are the usual ones — listed buildings and conservation areas, where, interestingly, an outbuilding install is often the winning consent strategy precisely because it spares the main roof). The cost advantage is practical: garage roofs are low. Less or no scaffolding, easier access, shorter working time — installs typically come in 10–15% below equivalent house-roof work. And output-wise, orientation is all that matters: a south-facing garage panel earns exactly what a south-facing house panel does. Physics doesn’t check the building type.
How many panels fit a garage?
| Garage type | Usable roof | Panels (450–500W) | System size |
|---|---|---|---|
| Single (pitched, good slope) | ~10–13m² | 4–5 | ~1.8–2.5kW |
| Single (flat, ballasted) | ~12–15m² | 4–6 | ~1.8–2.7kW |
| Double (pitched or flat) | ~25–30m² | 8–10 | ~3.5–4.5kW |
| Larger outbuilding / workshop | 30m²+ | 10+ | 4.5kW+ |
Quick self-check: modern panels run about 2m × 1.1m — call it 2.2m² each — so measure your usable roof, divide, and knock one off for edge margins. On pitched roofs only the well-oriented slope counts; on flat roofs the angled frames need row spacing to avoid shading each other, which trims the total. A double garage’s 8–10 panels is no toy — that’s 4kW-system territory, a proper household contribution. Our roof-fit calculator guide works for garages exactly as it does for houses.
The catch: flat roofs, ballast and prefab garages
The one-tonne problem
Here’s what the brochures skip. You can’t drill rail mounts into a flat roof — the holes leak — so flat-roof panels sit on angled A-frames held down by ballast: roughly 80kg per 20kg panel. That means a 10-panel ballasted array totals around a tonne, sitting on your garage roof through every storm. A solid concrete slab roof or well-built timber deck may shrug at that. A prefab concrete-panel garage or single-skin timber roof very often cannot take it — and plenty of British garages are exactly that. The related warning: countless older garage roofs are corrugated asbestos cement, and those should never be drilled or loaded — as our asbestos roof guide explains, replacement first is the only sensible route. None of this kills the project; it just means the structural check comes before the quote, and any installer who skips it is telling you something.
Costs — and the golden rule of garage solar
The economics split cleanly into two cases. Case one: the garage as an add-on. If you’re having house solar installed, adding the garage slope is the closest thing to free capacity in solar: labour, electrics and scaffolding dominate system costs, so extra panels on an easy low roof add little more than their hardware price. If your house roof is tight, shaded or nearly full, this is how you grow the system. Case two: the garage as the whole project — usually because the house roof is unsuitable (north-facing, shaded, protected). Standalone installs carry the full fixed costs, so scale matters: around six 450W panels (~2.7kW) is the sensible minimum, typically £4,000–£5,500 installed, with a double-garage 4kW system at £5,000–£7,000 — those 10–15% savings versus house-roof prices intact. Below six panels, grid-tied maths gets thin, and the off-grid route below beats it. Panel choice works exactly as on a house — the same brands, the same comparisons.
Detached garages: the wiring question
A detached garage’s panels still feed your house — the connection just travels. The standard method runs armoured SWA cable from the garage to your consumer unit or inverter position, either as AC from a garage-mounted inverter or as DC back to an inverter indoors. The cost lever is distance: a garage beside the house adds little; one at the bottom of a long garden means a trenched cable run that can add several hundred pounds. It remains one system on one supply — a single G98 notification covers it — and if the garage already has power from the house, the existing route often carries the new cabling. Worth noting the natural pairing while you’re at it: a garage with solar overhead is the perfect home for a smart EV charger — solar-aware charging where the car actually parks is one of the best-returning combinations in home energy.
Lights, door openers — and the garage heater truth
Not every garage needs a grid-tied system. If all you want is lighting, a door opener and somewhere to charge tools, a small off-grid kit does it for £150–£300: a 100W–200W panel, a charge controller and a leisure battery, with no G98 paperwork because it never touches the grid — a genuinely satisfying weekend DIY job, and the right tool for sheds and remote garages (our small panels guide covers the kit in detail). But we owe you honesty on the most-searched garage dream: solar garage heating. A 2kW fan heater burns more in one hour than a small array generates in an entire December day — heating demand peaks exactly when solar output troughs. Insulating the garage will make it warmer than any affordable panel setup ever will; if solar is to contribute to heat, it does so as a proper grid-tied system feeding the whole house, not a kit behind a heater.
Frequently asked questions
Can you put solar panels on a garage roof?
Yes — same permitted development rights as house panels (listed/conservation excepted), typically 10–15% cheaper to install thanks to easy low-roof access, and identical returns per panel when south-facing. The proviso: structure first — pitched roofs need sound rafters, flat roofs need to carry ballast.
How many panels fit?
Single garage: 4–6 panels (~1.8–2.7kW). Double: 8–10 (~3.5–4.5kW). Panels are ~2.2m² each, so measure and divide, minus edge margins. Flat-roof frames need row spacing, trimming the count slightly.
What does it cost?
As an add-on to a house install: little more than the hardware — the best value in solar. Standalone: ~six panels minimum to pay, £4,000–£5,500 for ~2.7kW, £5,000–£7,000 for a double-garage 4kW — 10–15% under house-roof prices.
What about flat garage roofs?
Ballasted A-frames only — roughly 80kg per panel, about a tonne for ten. Solid roofs cope; prefab concrete-panel and single-skin timber garages often can’t, and asbestos cement roofs should never be drilled or loaded. Structural check before quote, always.
How does a detached garage connect?
Armoured SWA cable back to the house consumer unit or inverter — AC or DC depending on design. Distance drives cost (trenching for long runs). One system, one supply, one G98 notification.
Can solar run garage lights, a door opener or a heater?
Lights and openers: easily — a £150–£300 off-grid kit (100W panel, controller, leisure battery), no paperwork. A heater: honestly, no — a 2kW heater out-consumes a small array’s whole winter day. Insulate instead, or feed heat from a full grid-tied system.
Great value roof — after the structural check
The bottom line: Garage roofs are underused solar real estate — same planning rights, 10–15% cheaper installs, same returns facing south. Add them to a house install for near-marginal cost, or go standalone from ~six panels (£4,000+). The gatekeeper is structure: ballasted flat-roof systems weigh a tonne, prefab and asbestos garages need care or replacement first, and any installer who skips the structural check isn’t your installer.
Get my free quotes →The verdict
The garage is British solar’s quiet bargain: a low, cheap-to-work, often perfectly oriented roof that most surveys walk straight past. Used as overflow on a house install it’s the cheapest capacity you’ll ever add; used alone it rescues homes whose main roof faces the wrong way or can’t be touched — including listed homes, where the outbuilding is often the roof that wins consent.
The honest gatekeeping matters, though: a tonne of ballast has no business on a prefab concrete garage, asbestos cement roofs need replacing before anything touches them, and a sub-six-panel grid-tied system rarely earns its fixed costs — that’s off-grid kit territory. The right first step is a survey that treats house and garage as one design problem: a couple of free, no-obligation quotes from MCS-certified installers — structural check included — will show you exactly what your roofs, together, can do.
Important
Going Solar UK is an introduction service, not an installer, structural engineer or planning adviser. This guide is general 2026 information, not professional advice. Garage structures vary enormously — always obtain a structural assessment before any roof-mounted installation, and confirm planning requirements for listed buildings, conservation areas or unusual cases with your local authority. Costs and savings are typical estimates, not guarantees.
We may receive a commission when we introduce you to an installer, at no cost to you. Any contract for work is directly between you and the installer.