Solar Panels for Sheds — Power at the Bottom of the Garden

Getting mains electricity to a detached shed is more expensive than most people expect. The cable has to be steel-wire armoured, buried at depth or clipped along a permanent structure, fed from a spare way on the consumer unit, and — because it is a new circuit in a special location — the work falls under Part P of the Building Regulations, which in practice means a registered electrician and a certificate. By the time the trench is dug and the paperwork is done, £800–£1,500 has gone, and the shed still consumes billed electricity every time the light goes on.

A solar setup inverts that economics. The panel, charge controller, battery, and lights for a typical shed cost less than the trench alone, take an afternoon to fit, and generate free electricity for twenty years or more. Low-voltage DC systems — the kind most sheds need — sit outside Part P entirely, so a careful DIYer can do the whole job legally. There is no meter, no standing charge, and no cable for a spade to find.

The honest caveat is capacity. A shed solar system is a budget, not a tap. Every panel watt and battery amp-hour is a hard limit on what you can run, which is why this site keeps returning to one discipline: add up your real loads first, then buy. A 100W kit that powers LED strips brilliantly will stall a 2kW table saw without ceremony. Match the system to the job and shed solar is the cheapest electricity you will ever own; mismatch it and the kit ends up on a classified ad. Start with our shed solar kit guide to find your tier, then sanity-check the numbers on the costs page.

Every regretted shed solar purchase starts the same way: someone buys the panel first and discovers the limits later. The reliable method runs in the opposite direction. Write down each thing you want to run, its wattage, and how many hours a day it runs. Multiply and add. Six 5W LED lights for three evening hours is 90 watt-hours. A laptop charger at 65W for four hours is 260Wh. A 40W soldering iron for an hour adds 40Wh. That imaginary shed needs roughly 400Wh a day — winter included if you use it year-round.

Then size backwards from the worst month. A south-facing panel in the UK yields around 0.6–0.8 kWh per day per kW of panel in December, against 4 kWh or more in June. To cover 400Wh a day through winter you want at least 300W of panel and a battery that holds two to three days of use — call it 100Ah of lithium at 12V. In summer the same system will be embarrassingly oversupplied, which is the correct way round. The worked sizing example on the blog walks through three real shed loadouts step by step.

Two figures deserve special respect. Surge: motors in saws, compressors, and fridges draw two to three times their rated wattage at start-up, and the inverter must cover the surge, not the sticker. And depth of discharge: a 100Ah lead-acid battery offers about 50Ah of usable capacity before its lifespan collapses, while lithium gives 80–90Ah. Cheap kits quote the headline number; your shed runs on the usable one. Both pitfalls are covered properly in the battery guide.