Panel installation and wiring
Solar Panels on a Shed or Outbuilding: UK DIY Guide
Your garden shed or garage roof may be the easiest solar surface you own. It requires no scaffolding, no planning permission in most cases, and it can be done without touching your house's electrics if you take the off-grid route. A UK creator built a full 3.3kW array on a garden shed and documented the whole process. Here is what to know before you start.
1. Decide between off-grid and grid-connected before buying anything
This choice shapes everything else, including the components you buy, the permissions you need, and the payback calculation.
An off-grid shed system stores energy in a local battery bank and powers the shed's own loads, such as lighting, tools and a small fridge. It needs no DNO notification, no electrical inspection and no MCS involvement if it stays entirely within the shed and does not connect to the house. The downside is that surplus generation cannot be used inside the house, and you cannot earn Smart Export Guarantee payments.
A grid-connected system sends surplus generation back through the house electrical system, reducing your import and potentially qualifying for SEG export payments. It is the better long-term investment but requires a G98 application to your DNO before energising, a certified installer to make the consumer unit connection, and compliance with BS 7671. Larger systems (above 16A per phase) require G99 rather than G98.
2. Check the roof area, orientation and planning rules
Measure your south-facing roof carefully. A standard 8 by 6 foot shed has around 4.5 square metres of usable roof, enough for two 400W panels with walking clearance. A 12 by 8 foot workshop with a proper pitched roof offers around 8 to 10 square metres and can take 4 to 6 panels. A garage roof of 15 to 20 square metres can accommodate 6 to 8 panels for 2.5 to 3.3kW or more.
On planning: in England, fitting solar to an outbuilding is permitted development in almost all cases, subject to the 200mm protrusion limit and the usual exceptions for listed buildings and conservation areas. If you are unsure about your site, the Planning Portal's interactive guide covers outbuildings as well as houses.
Use PVGIS to calculate expected annual output at your exact orientation and roof pitch. This will tell you whether the project makes economic sense before you spend anything.
3. Size your panels and inverter to match the available roof
For a grid-tied system, a string inverter is the most common and cost-effective choice for a straightforward shed roof with consistent orientation. A 3kW inverter handles a 6 to 8 panel string, and most models from Solis, SolarEdge, Fronius and Growatt are well-suited to shed installations.
If your shed roof is partially shaded during the day from trees, neighbouring buildings or a dormer window, consider power optimisers or module-level electronics at each panel. Tigo optimisers, which were used in the NCoT shed project with 415W Trina panels, allow each panel to operate at its individual maximum power point rather than being dragged down by a shaded neighbour in the string.
For an off-grid system, size the battery first. Decide how much storage you need overnight or on a dull day, then size the panels and charge controller to replenish that storage comfortably during summer and with acceptable shortfall in December and January.
4. Mount the panels and run the DC cable to the inverter
Shed roofs vary considerably. A metal sheet roof will accept standard L-feet that clamp through the corrugation to the rafters below. A felt roof on a timber-framed deck needs roof hooks or L-feet that bolt through the decking into the rafters, sealed with EPDM or butyl tape to prevent water ingress at the penetration.
Do not attach rails or L-feet solely to the felt or sheet covering without fastening through to a structural rafter. Panel plus rail weight, combined with wind loading, will pull fixings through thin decking over time.
DC cable from the panels to the inverter should be rated for PV use (PV1-F or H1Z2Z2-K), UV-stabilised and run in conduit where it is exposed to sunlight or weather. Keep the cable run as short as possible to reduce resistive losses and cost. The inverter should be inside the shed in a dry location, not mounted outdoors on the shed wall where it will be exposed to direct rain.
5. Connect to the grid or battery, and register if required
For a grid-tied system, the AC output from the inverter goes to a dedicated circuit in the house consumer unit via a cable run from the shed. This connection must be made by a qualified electrician, and the installation must comply with BS 7671. Your DNO G98 application must be submitted and accepted before you energise the system. The application is straightforward and most DNOs respond within a few working days. Once live, register with a Smart Export Guarantee supplier to receive export payments.
For an off-grid system, connect the charge controller output to your battery bank, sized to handle the peak current from the panels. Connect your DC loads directly or feed a battery inverter for AC loads in the shed. There is no DNO, no registration and no inspection required for a self-contained off-grid system.
Either way, document the installation: photographs of the wiring, cable routes, panel mounting and serial numbers. This is useful for insurance claims, future maintenance, and any future MCS upgrade if you later decide to go grid-connected.
Frequently Asked Questions
Do I need planning permission to put solar panels on a shed in the UK?
Usually no, in England. Adding solar to a garden shed or outbuilding is permitted development for most homeowners, provided the panels do not protrude more than 200mm beyond the roof plane and the shed is not in the curtilage of a listed building or in a conservation area. Wales and Scotland follow similar principles under their own permitted development rules. If in doubt, a check with your local planning authority before you buy is much faster than undoing the work later.
Can shed solar panels export to the grid and earn SEG payments?
Yes, but only if the system is grid-connected through an MCS-certified installer with a G98 notification submitted to your DNO before energising, and you register with a Smart Export Guarantee licenced supplier. A purely off-grid shed system cannot export to the grid or earn SEG payments. The MCS route adds cost and planning but is the only way to receive payment for surplus generation.
What size solar system fits a typical garden shed?
A standard 8 by 6 foot garden shed fits two 400W panels for around 800W total. A 12 by 8 foot workshop can take 4 to 6 panels at 1.6 to 2.5kW. A garage or large outbuilding with 15 to 20 square metres of south-facing roof can take 6 to 8 panels at 2.5 to 3.3kW. A UK creator fitted 8 panels of 415W each on a garden shed, giving a 3.3kW array with a Solis inverter and Tigo optimisers, which produced meaningful year-round output and was judged worth the cost.