Not all solar canopies are built the same way. The frame geometry you choose drives almost everything that matters commercially: how much electricity the array generates, how much steel and concrete the project consumes, how high the clearance is for vehicles, and how the foundations interact with what is already buried under your car park. Get the structure type right and you optimise yield against cost. Get it wrong and you either overspend on steel or leave generation on the table.
This guide compares the three structures that account for the overwhelming majority of UK commercial solar canopy installations — mono-pitch, T-frame, and cantilever — on the metrics that decide a business case. We are looking purely at the engineering trade-offs here, not the funding routes (covered separately in our finance guides).
The Three Structure Types at a Glance
Every solar canopy is a steel frame holding a PV array over a usable surface — usually parking, occasionally a walkway, loading yard, or amenity space. What separates the structure types is how the array is supported and pitched.
A single-slope (mono-pitch) canopy tilts the whole array in one direction across a single run of supporting columns. A T-frame canopy uses a central spine of columns with the array spreading out on both sides, like a butterfly or inverted-V. A cantilever canopy supports the array from columns set to one side only, so the deck projects outward with no posts on the far edge.
Each geometry exists because it solves a different site problem. Below we break down the engineering of each, then bring it together in a single specification table.
Mono-Pitch (Single-Slope) Canopies
The mono-pitch canopy is the workhorse of UK commercial solar canopies. The entire array sits on a single plane, pitched typically at 5–10 degrees in one direction. Columns run along one or both edges of a single bay run.
Yield
Single-slope geometry is the strongest performer per panel because every module shares the same optimal orientation. Where the run can be aligned south, south-east or south-west, a mono-pitch array captures the best of the available irradiance with uniform module performance and minimal inter-row variance. On an unshaded south-facing run you are realising close to the theoretical maximum for a fixed-tilt commercial array.
Cost per kWp
Mono-pitch is also the most steel-efficient layout for straight, single-aisle car park runs, which keeps it at the lower end of the UK solar canopy range of £900–£1,400 per kWp. Simpler connections, fewer column types, and a repeatable bay module mean fast fabrication and installation.
Access Height & Foundations
Clearance is set by the low edge of the slope, so designers must size columns to keep the low side above the 2.2–2.6 m vehicle clearance most car parks require. The high edge matters just as much for consent: in England, Class OA permitted development stops once any part of a canopy is more than 4 metres above ground level (how canopy planning works). Foundations are typically pad or screw-pile under each column line — straightforward where ground conditions are known, though a single-sided column run carries more lateral load and may need larger pads.
Best Use Case
Long, straight parking aisles; sites with a clear preferred orientation; budget-led projects where cost per kWp is the deciding metric. It is the default recommendation for most retail, school, and office car parks. Explore the full layout options on our mono-pitch canopy page.
T-Frame Canopies
The t-frame canopy places a single line of columns down the centre, with the array fanning out symmetrically to both sides — covering a double row of parking bays back-to-back from one foundation line.
Yield
A T-frame typically splits the array into two pitched planes facing opposite directions (often east/west or both pitched off a north–south spine). East/west arrays sacrifice a few per cent of peak yield versus a perfect south slope but spread generation across the day, producing a flatter curve that often matches a business’s load profile better — useful for sites that want self-consumption rather than peak export. Total annual yield per kWp lands a little below mono-pitch but the day-shape can be more valuable.
Cost per kWp
The shared central spine halves the number of column lines for a given covered area, which is materially efficient where you are roofing a double bay. Foundation count drops, but each footing carries more load. Net cost per kWp is comparable to mono-pitch, sometimes slightly higher because of heavier central members and more complex connections.
Access Height & Foundations
Central columns keep the perimeter completely post-free, which is excellent for vehicle manoeuvring and bay access. The trade-off is that the central foundations are larger and more heavily loaded, so ground investigation is more important. T-frames suit deeper pad or piled foundations.
Best Use Case
Double rows of parking served from a central aisle; sites where perimeter access matters; businesses prioritising an even, all-day generation profile. See typical spans and bay configurations on our t-frame canopy page.
Cantilever Canopies
The cantilever canopy is the architectural and access-driven option. Columns sit on one side only and the deck projects outward, leaving the far edge entirely free of structure.
Yield
Cantilever decks are usually mono-pitched, so per-panel yield is close to a single-slope array — the geometry is about support, not orientation. You keep strong generation while removing posts from the protected side.
Cost per kWp
This is the most expensive structure type per kWp. Projecting an unsupported deck means heavier columns, larger moment-resisting connections, and substantially bigger foundations to resist the overturning load. Expect to sit at the upper end of the £900–£1,400/kWp band, occasionally beyond it for long projections.
Access Height & Foundations
Cantilever excels where you cannot place columns in the covered zone — over an existing pedestrian route, a drive-through lane, drainage runs, or where a single column line must sit on a kerb or verge. Foundations are the critical engineering element: the single column line takes the entire vertical and overturning load, demanding deep piles or mass concrete and thorough ground investigation.
Best Use Case
EV charging bays where charger access must stay clear; entrance canopies and drop-off zones; sites with buried services on one side; any layout where a post-free far edge is non-negotiable. Full projection limits are on our cantilever canopy page.
Specification Comparison
| Metric | Mono-Pitch (Single-Slope) | T-Frame | Cantilever |
|---|---|---|---|
| Relative annual yield/kWp | Highest (single optimal plane) | Slightly lower (split E/W, flatter curve) | High (mono-pitch deck) |
| Cost per kWp (UK 2026) | £900–£1,150 | £1,000–£1,250 | £1,150–£1,400+ |
| Typical pitch | 5–10° single slope | Dual slope off central spine | 5–10° projecting deck |
| Column lines | One or both edges | Single central spine | One side only |
| Vehicle clearance | 2.2–2.6 m at low edge | 2.4 m+, post-free perimeter | 2.4 m+, post-free far edge |
| Foundation demand | Moderate pad/screw-pile | Heavier central footings | Highest — deep piles, overturning load |
| Generation profile | Peaky (orientation-led) | Flat all-day (E/W) | Peaky (orientation-led) |
| Best for | Straight aisles, budget builds | Double bays, even load match | EV bays, buried services, clear edges |
All three structures take bifacial panels, which add roughly 8–15% extra yield on a canopy by capturing light reflected off the deck soffit and the surface below — typically the best incremental return you can specify on any canopy regardless of frame type.
How to Choose
Work through it in this order:
- Site constraints first. Buried services, an existing pedestrian route, or a drive-through lane on one side pushes you toward cantilever before any other consideration. A central aisle serving a double bay points to a T-frame.
- Orientation second. A clear south-ish run with no access constraint makes mono-pitch the efficient choice. No usable single orientation, or a strong preference for all-day self-consumption, favours a T-frame’s east/west split.
- Budget and yield third. Where the first two are open, mono-pitch usually wins on cost per kWp and total yield. Reserve the premium of a cantilever for where its access benefit genuinely earns its keep.
In practice many car parks end up with a hybrid — mono-pitch over the long straight runs, a cantilever section over the EV bays or entrance, and a T-frame where a double row shares a central aisle. The structures are not mutually exclusive across a site, and a good feasibility study will mix them to optimise the whole layout rather than forcing one geometry everywhere.
Next Steps
The right structure is a function of your specific car park geometry, ground conditions, and load profile — it is not a catalogue choice. A proper feasibility study models all three against your site, your orientation, and your electricity demand curve, then sizes the system that delivers the best return.
Browse the full range of frame configurations and span options across our systems overview, or go straight to the dedicated pages for the mono-pitch canopy, t-frame canopy, and cantilever canopy to see the engineering detail, typical spans, and where each one fits best.
Keep the structure and the generation plant as separate contract lines — it matters for solar canopy business rates. The specification and cost bands for commercial solar carports are set out in full on our dedicated page. Which structure suits your bay layout, and what each format costs to build, is compared on our solar panel canopy page.
If the site has unused land as well as a car park, the structural choice widens again — solar carport or ground-mount compares the two on consent route, cable run and land value rather than on cost per kWp alone.
Related: the structure you choose also fixes the clear height under the canopy, which decides whether the 4 m planning cap can be met, and the choice belongs in the tender specification.
Over a car park, the structure and the bay layout fix each other; the car park solar canopy page works from the bay count to capacity and yield.