Solar Power for a Garden Office or Summerhouse

Search for solar panels for a garden office and you will find a long list of kits for sale and very little about whether any of them will do what you want. The honest answer depends almost entirely on one question that most of those pages skip: are you trying to heat the building?

Everything else about a garden office is easy to power. Heating is not, and it is the thing that decides whether you buy a £330 kit or call an electrician.

Why a garden office is not a shed

Most solar advice for garden rooms is recycled shed advice, and it does not transfer cleanly. A shed is a place you visit. An office is a place you sit in for eight hours, usually in the colder half of the year, with equipment running the whole time.

That changes two things. The first is duration — a shed light is on for twenty minutes, an office runs all day, so you are sizing a battery for sustained draw rather than occasional use. The second is comfort. Nobody expects a shed to be warm. An office in February has to be, or you will not use it, and that single requirement is worth more than everything else on the list put together.

If your building is genuinely a summerhouse — used in the warm months, for sitting in rather than working in — then the shed advice does apply, and our shed solar guide covers it well.

What solar comfortably runs

The working parts of an office are modest. A laptop draws 30-65W depending on what it is doing, an external monitor 20-30W, a router around 10W, and LED lighting 10-20W. Add phone charging and you are looking at roughly 150W continuous through a working day.

Over eight hours that is about 1.2kWh. A 400W array in reasonable British conditions will generate that across a day for most of the year, and a 100Ah lithium battery holds enough to carry you through a grey one and into the evening. This part genuinely works, and it works without an electrician, without notifying anyone, and without a trench across your lawn.

What it means in practice is that an unwired garden office can be a completely functional workspace on solar alone — right up to the point where you want it warm.

The heating problem, honestly

A small fan heater or panel heater draws 1,000-2,000W continuously. That is roughly ten times everything else in the building combined.

Run a 1.5kW heater for four hours and you have used 6kWh. Your entire office setup uses 1.2kWh in a full day. So heating does not add to your load — it replaces it as the only number that matters, and it multiplies your system by a factor of five or more.

Then the seasons make it worse. You want that heat in December and January, which is precisely when a UK solar panel produces least — a small fraction of its June figure. The demand peaks exactly as the supply bottoms out. There is no clever sizing that fixes that, because the problem is not the kit, it is the British winter.

This is why kit sellers tend to be vague about heating. A kit that genuinely heated a garden office through a British January would cost more than the office. If a product page implies otherwise, check what wattage it is actually claiming and for how many hours.

The workable compromises are worth knowing. Insulate properly first, because a well-insulated garden room holds heat far better than most people expect and needs the heater on far less. Consider heating the person rather than the room — a heated chair pad or a small under-desk panel draws a fraction of a room heater. And accept a shoulder-season office rather than a year-round one, if that fits how you actually work.

The two honest routes

Almost everyone ends up on one of these, and choosing early saves money.

Route one — off-grid kit, no mains. A panel, a battery, a charge controller and an inverter, sitting entirely within the garden room. It powers the work, not the warmth. No electrician, no building control, no connection to the house. This is the right answer for a summerhouse, a studio, a three-season office, or anywhere running a cable would mean digging up something you would rather not.

Route two — mains cable, then solar on top. Get a proper supply out there, use electric heating as needed, and treat solar as a way to reduce the bill rather than replace the supply. More expensive up front and it needs a qualified electrician, but it is the only route that gives you a genuinely year-round office.

The mistake to avoid is starting down route one, discovering in November that you are cold, and then buying route two anyway — having already spent several hundred pounds on a kit that is now doing a job the mains could do.

Running mains properly

If you take route two, this is not a weekend job with an extension lead.

Running a new supply to an outbuilding is notifiable work under Part P of the Building Regulations in England and Wales. It has to be carried out by an electrician registered with a competent person scheme, who can self-certify the work, or else inspected by your local authority building control. You should end up with an Electrical Installation Certificate confirming compliance with BS 7671.

The standard method is steel wire armoured cable — SWA — either buried in a trench at around 500mm depth or surface-run along a wall or fence. Cable size depends on the length of the run and the load, so a long run to a building with a heater needs heavier cable than a short run to a lighting circuit.

Running a permanent extension lead across the garden instead is both a fire risk and a trip hazard, and it will not satisfy anyone if you come to sell the house.

One thing to note if you go grid-tied: connecting a generating system to your home supply brings your network operator into it, which usually means a G98 notification. Our G98 notification guide covers when that applies and how it works. A standalone off-grid kit has no grid connection at all, so none of that paperwork touches it.

Sizing an off-grid office kit

Work from hours of use rather than from the building.

100W panel, small battery. Lighting, charging, a speaker. A summerhouse, or an office you use occasionally in good weather.

400W panel, 100Ah lithium, pure sine inverter. The realistic choice for anyone actually working out there. Laptop, monitor, router and lighting for a full day, with enough battery to ride out a grey one. Pure sine matters here — cheap modified sine inverters can upset laptop chargers and monitors.

800W or more, 200Ah plus. Sensible if you run desktop equipment, multiple monitors, or want genuine multi-day autonomy in winter. This is also roughly where the cost starts to approach a mains connection, so compare the two before committing.

Independent guides broadly agree on the shape of this. One puts a typical 4x4m garden office at six to eight panels for a full roof system, with at least 500W and a 200Ah battery for a working off-grid setup; another suggests 500W to 1.5kW with a modern battery for a summer house. The gap between those numbers is mostly about whether heating is in scope.

Real UK prices

Prices listed by UK retailers in August 2026. They move, so treat these as the shape of the market rather than a quote.

For scale at the top end, one garden room manufacturer quotes £6,354 for eight panels with a battery on a garden room, against an annual electricity bill saving of £918 — around a seven-year payback before you account for anything else. That is a whole-property decision rather than a garden office one. If you want to run those numbers for your own situation, our payback calculator handles it.

Recommended kit

If you are assembling from parts rather than buying a bundle, our solar accessories guide covers the cabling, connectors and glands that kits leave out, and the battery storage guide goes deeper on sizing the bank itself.

Summary — what to buy

• Decide about heating first. It is the only question that changes the answer.
• Working office, no heat needed? A 400W kit with a 100Ah lithium battery and a pure sine inverter, around £330-£500.
• Summerhouse or occasional use? A 100W kit at £120-£180 is plenty.
• Want it warm in January? Run SWA cable and get a proper supply. It is notifiable under Part P and needs a registered electrician.
• Insulate before you buy anything. It reduces the heating problem more cheaply than any panel.

If the garden also has a greenhouse, see solar power for greenhouses for the jobs solar does well there, and solar shed lights for a cheap light in a tool store.

Frequently Asked Questions

Last updated: September 22, 2026