Ground Mount vs Roof Mount: Where Should the Panels Go?

Yield: ground wins, by a real margin

The roof gets the orientation and pitch the builder chose in 1987; the ground frame gets due south at 35 degrees because you said so. Add ventilation — free-standing panels run cooler, and panels lose about 0.35% of output per degree of cell temperature — plus the cleaning nobody ever does at gutter height, and a garden array typically returns 10–15% more annual energy than the identical panels on an average UK roof. If your roof happens to be a south-facing 35-degree slope with no chimney shadows, that margin shrinks toward zero; if it is east-west, hipped, and dormered, the margin widens past 20%. Step one of the comparison is always: how good is your specific roof, honestly?

Cost: roof wins, usually

Roof installs amortise their scaffold across a process the industry has done a million times: £1,000–£1,300 per kWp for a straightforward 3–4kWp roof job in 2026. Ground mounts add groundworks, frames, and a trench: PD-sized arrays land £2,200–£3,500 for 1.8kWp (£1,200–£1,900 per kWp — small systems carry the fixed costs heavily), improving to £1,100–£1,400 per kWp at consented 4kWp scale. Both routes are zero-rated for VAT until March 2027 when professionally installed. The cost gap narrows where the roof is the awkward one: conservation rooflines, fragile slates, deep dormers, or three-storey scaffold all add roof-side hundreds that the lawn never charges.

Planning: roof wins on paper, ground wins on certainty

Roof solar on a house is often permitted development with generous limits; stand-alone garden arrays carry the tight 9m²/4m/5m-from-boundary conditions and one-per-property rule covered on the planning page. But there is a twist: when a ground array does need consent, the application is decided on visibility and neighbour amenity — things you can design for — whereas a refused roof (listed building, Article 4 street) is often simply refused. Gardens offer fallback positions; roofs offer one.

Maintenance and lifetime: ground, quietly

Panels are warranted for 25 years; the question is everything around them. A ground array is inspected from a deckchair, cleaned with a hose, and its inverter lives in a garage at human height. A roof array shares its fate with the roof — and re-roofing under a 15-year-old array means paying to remove and refit the system (£1,000+) at exactly the moment the roof bill lands. If your covering has a decade left, sequence matters: roof first, panels after, or panels in the garden and the roof's problems stay its own. Bird-proofing, a £300–£600 roof-array line item where pigeons operate, is another invoice the lawn never sends.

The lawn question, and the honest verdict

Ground mounts spend a currency roofs do not: garden. Nine square metres of panel plus working clearance is a real bite from a small plot, and unlike the panels, the lawn's value is set by your household's politics. Families with children and modest gardens routinely — and correctly — pay the roof's yield penalty to keep the grass. Households with long gardens, paddock corners, or a dead zone behind the greenhouse give up nothing at all.

The verdict pattern from running this comparison many times: good south roof, tight garden — roof, easily. Poor roof, generous garden — ground, easily. Middling both — roof for pure payback, ground if you value yield, inspectability, and keeping the house untouched; and consider the hybrid (outbuilding roofs count as the generous planning category while sitting at garden height — frequently the best of both). Whichever way you lean, run the shade-watch on the garden option before deciding: one Saturday of photography settles arguments that brochures cannot. Then price the winner on the costs page.