Garden Solar Questions, Answered with Numbers

In England, stand-alone garden solar is often permitted development up to 9 square metres of panel area — roughly four modern panels, about 1.8kWp — provided it is the property's first stand-alone array, stands under 4 metres tall, sits at least 5 metres from every boundary, and the property is not listed (conservation areas add conditions). Beyond any of those limits you apply for householder planning permission. Wales, Scotland, and Northern Ireland differ in detail. Always confirm with your Local Planning Authority — interpretations vary and PD rights are sometimes removed locally.

Because it disqualifies more gardens than the size cap does. The permitted development conditions require the whole installation to be at least 5 metres from every boundary of your property's curtilage — so a garden 10 metres wide leaves effectively no qualifying space, regardless of how small the array is. If your garden fails this test, the route is a standard householder planning application (£258 in England), which garden arrays pass routinely when siting and neighbour amenity are addressed.

A well-sited south-facing array produces roughly 850–1,050kWh per year per kilowatt installed depending on region — so a PD-sized 1.8kWp array yields around 1,600–1,800kWh, and a consented 4kWp array around 3,600–4,000kWh. Ground mounts typically beat the same panels on a compromised roof by 10–15% thanks to ideal angle, cooler running, and easy cleaning. December output is about a fifth of June's — relevant mainly to off-grid designs.

Through buried steel-wire armoured (SWA) cable, typically 450–600mm deep with warning tape, sized for the distance to keep volt-drop sensible. Connection at the consumer unit is notifiable electrical work for a registered electrician, and grid-tied systems need a DNO notification (G98 up to 3.68kW per phase, G99 application above). An MCS installer handles all of this as standard — and MCS certification is what makes you eligible for Smart Export Guarantee payments.

Installed ground arrays: £2,200–£3,500 for a PD-sized 1.8kWp system, or £1,100–£1,400 per kWp for larger consented arrays. Solar pergolas: £4,000–£6,500 for a 3×4m system around 2kWp. Off-grid garden room systems: £1,800–£2,600 in parts. Central-panel lighting systems: £350–£500. Professionally installed systems are zero-rated for VAT until 31 March 2027; DIY parts carry 20%.

There is no general grant, but two mechanisms matter. The 0% VAT rate on professionally installed domestic solar (including ground mounts and pergola systems) runs until 31 March 2027 — effectively a 16.7% discount against the old standard rate. And the Smart Export Guarantee obliges larger electricity suppliers to pay for exported units; rates vary from about 4p to 15p+ per kWh, so it pays to shop the tariff, not just the install.

More than intuition suggests, because panels in a string behave like a hosepipe with a kink: shading one panel can drag down the whole string's output. An hour of hard midday shadow across part of the array in each day can cost 20–30% of annual yield, not the few percent the shaded area implies. Watch the proposed site across a full sunny day before committing, and if partial shade is unavoidable, specify micro-inverters or optimisers so each panel performs independently. Our blog article on shade walks through the numbers.

Yes — either a house battery charged by the array like any other solar input (£2,000+ installed, judged on its own payback), or, for off-grid garden projects, a 12V/24V lithium battery at the heart of the system. For grid-tied gardens the battery decision is independent of the mounting: get the array economics right first, then add storage if your tariff and usage pattern justify it. Time-of-use tariffs that charge the battery cheaply overnight often beat adding more panels.

Modern panels carry 3.2mm+ tempered glass rated for 25mm hail and survive most garden life; the realistic risks are edge impacts from mowers and strimmer stones. Practical mitigations: gravel or membrane strip around the frame, a low rail or planting in front of the panel faces, and siting away from the goalmouth. Panel glass that does break is visually obvious and a warranty/insurance conversation — keep the install photos and serial numbers.

Declare any installation to your insurer; ground arrays and pergola systems are usually covered as garden structures or fixtures with no premium change, but undeclared kit is the classic claims dispute. On resale, an owned, MCS-certificated array with paperwork transfers cleanly and surveys well; keep the MCS certificate, DNO confirmation, and electrical certificates together. A Lawful Development Certificate (about £129) is cheap belt-and-braces if there was any planning ambiguity.

Badly sited ones are. The difference is almost always siting and finishing rather than the hardware: all-black panels on a low frame, gravel and planting at the base, and placement that uses an existing sight line (along a fence run, behind the greenhouse) read as garden infrastructure rather than industry. Pergola systems go further and make the panels the architecture. What rarely works is the compromise nobody chose deliberately — a high frame in the middle of the lawn because the cable run was cheapest.

Partially. The permitted development allowance covers only the first stand-alone installation, so a second separate array later generally needs planning permission even if it is tiny. Practical expansion strategies: size the inverter and cable run for the array you eventually want; use a garden building roof (which follows different, more generous rules) for phase two; or take the consent route once for the full design and build it in stages.