The single most common question facilities managers and finance directors ask is deceptively simple: how many solar panels fit on our car park? The honest answer is that it depends on bay geometry, panel wattage, structure type and shading — but you do not need a feasibility study to get a working number. This guide gives you the real engineering figures: panels per bay, kWp per car park, and annual generation for every common site size from 20 to 500 spaces.
If you take one rule of thumb away, make it this: a standard UK parking space supports roughly 1.7 kWp of solar canopy capacity after allowances for access, spacing and structure. Everything below builds on that number.
How Many Solar Panels Fit Over One Parking Bay?
A standard UK car parking bay is 2.4m wide by 4.8m long — about 11.5m² of plan area. A modern commercial solar panel (450–550W) measures roughly 1.13m × 2.28m, or about 2.58m² each.
In practice you do not tile a canopy bay-for-bay with panels touching the kerb lines; you size the canopy roof to the structural grid, which usually overhangs the bays slightly for weather protection. The working figures used at design stage:
| Per single bay | Figure |
|---|---|
| Plan area | ~11.5 m² |
| Panels that fit | about four modules after allowances |
| Installed capacity | about 1.7 kWp per space |
| Annual generation (Great Britain) | about 1,370–1,610 kWh per space (PVGIS 5.3, 10° pitch) |
The 1.7 kWp per space figure is the number that matters (the derivation is on the car park solar canopy page: a 2.4 × 4.8 m bay is about 11.5 m², and modules cannot cover all of it once access, spacing and structure are allowed for). Mono-pitch and duo-pitch canopy structures both land here; mono-pitch tilts the whole array to one side for a cleaner south-facing yield, while duo-pitch (the “butterfly” or A-frame) splits east/west and is more space-efficient over double-bay rows. For most UK car park canopies projects, mono-pitch is the usual choice where orientation allows and duo-pitch where the rows run the wrong way for a single tilt.
Why bifacial panels change the maths
Solar canopies are one of the few applications where bifacial panels genuinely earn their premium. Because the array sits high off elevated steel with light-coloured tarmac or concrete beneath, the rear face captures meaningful reflected and diffuse light. Expect a +8–15% generation uplift versus the same monofacial array — which is why bifacial modules are now the norm on canopies. The tables below use a conservative mid-range yield that already assumes bifacial gain.
kWp by Car Park Size: The Sizing Table
Here is the headline reference. These figures assume usable bays (deduct disabled bays adjacent to entrances, EV bays you want to keep open, and any bays lost to columns), a design density of about 1.7 kWp per space, and a UK generation yield of roughly 850 kWh per kWp per year for a well-oriented canopy. Latitude moves that figure more than most sizing tools admit: at a 10° canopy pitch, PVGIS gives about 920 kWh per kWp a year in London, 805 in Edinburgh and 772 in Glasgow, so northern sites should adjust — see our guide to solar canopies in Scotland.
| Spaces covered | Canopy kWp | Panels (approx.) | Annual generation | Annual CO₂ saved |
|---|---|---|---|---|
| 20 spaces covered | 34 kWp | 79 | ~29,000 kWh | ~6 tonnes |
| 50 spaces covered | 85 kWp | 198 | ~72,000 kWh | ~14 tonnes |
| 100 spaces covered | 170 kWp | 395 | ~144,000 kWh | ~28 tonnes |
| 200 spaces covered | 340 kWp | 791 | ~289,000 kWh | ~57 tonnes |
| 500 spaces covered | 850 kWp | 1977 | ~722,000 kWh | ~142 tonnes |
A few things to read into this table:
- You rarely canopy 100% of bays. Real coverage is typically 70–90% of the car park once you exclude access routes, drainage, columns and bays you want kept clear. The table counts spaces actually covered, so for a 100-space car park with 70–90% coverage expect about 120–150 kWp.
- The 100-space site is a useful reference point. At about 120–170 kWp it is large enough to justify the fixed costs of structural steel and grid connection, while usually staying under the half-megawatt threshold where DNO connection costs and timelines escalate.
- Above ~1 MWp, the grid connection becomes the gating factor, not the roof. A 500-space car park can physically host roughly 0.6–0.8 MWp, but whether you can export — or even import-offset — that much depends entirely on your DNO capacity.
Will My Site Use All That Power?
Generating the electricity is only half the equation; the value comes from self-consumption. A canopy generates a near-perfect daytime curve (peaking 10:00–15:00), so sites with strong daytime load capture the most value.
| Site type | Typical self-consumption | Why |
|---|---|---|
| Office / business park | 70–85% | Daytime occupancy matches generation |
| Retail / supermarket | 80–90% | Refrigeration + lighting all day |
| Hospital / 24-7 site | 85–95% | Constant base load |
| Leisure / evening venue | 40–60% | Load peaks after the sun drops |
Whatever you do not self-consume is exported. Under the Smart Export Guarantee (SEG), UK suppliers pay between 4p and 15p per kWh for exported electricity — so even a leisure site with poor daytime overlap monetises its surplus. Pairing a canopy with battery storage lifts self-consumption substantially, which is increasingly how larger schemes are designed. The full economics, including SEG and battery payback, are broken down on our cost page. For a worked example of how weak daytime overlap stretches payback, see solar panels for sports clubs.
What Does a Solar Canopy Cost at Each Size?
Solar canopies cost more per kWp than a rooftop array because you are paying for engineered steel that has to carry wind and snow loads while spanning vehicles. The current UK installed range is £900–£1,400 per kWp depending on structure type, ground conditions, and whether EV charging is integrated.
| Car park size | Canopy kWp | Indicative installed cost |
|---|---|---|
| 20 spaces | 60–80 kWp | £55k–£110k |
| 50 spaces | 150–200 kWp | £135k–£280k |
| 100 spaces | 300–400 kWp | £270k–£560k |
| 200 spaces | 600–800 kWp | £540k–£1.1m |
| 500 spaces | 1.5–2.0 MWp | £1.35m–£2.8m |
Two factors pull you toward the higher end of the per-kWp range: poor ground (deep piling on made ground or contaminated land), and integrated EV charging with its own civils and distribution. Two factors pull you lower: a clean structural grid that lets you repeat one bay design across the whole car park, and a single large array that amortises the inverter and grid-connection costs.
The tax position makes the net cost much lower
For UK businesses, the Annual Investment Allowance (AIA) lets you deduct 100% of qualifying plant in the first year. At the 25% main rate of Corporation Tax, that effectively cuts the net cost of a £400k canopy by £100k in year one. Public-sector sites — schools, NHS trusts, councils — cannot rely on PSDS (closed to new applications in November 2024) or a Salix loan (none exists for English public bodies); see the PSDS funding position for what they use now.
Planning: Will You Need Permission?
Most freestanding solar panel canopy structures over an existing car park can use permitted development in England through Class OA of Part 14 (prior approval always required, 4 metres maximum height); Class A.2(b) and Class J cover equipment on or near buildings, not a free-standing canopy. The practical limits to watch:
- Listed buildings (curtilage) are outside Class OA, so assume a full application; in conservation areas prior approval also weighs the canopy’s appearance.
- Height and proximity to boundaries can tip a project out of PD; canopies are tall, so check the site’s relationship to the highway and neighbours.
- Visibility from a principal elevation facing a road can trigger conditions even where PD nominally applies.
In England, a canopy over off-street non-domestic parking can use permitted development Class OA, which always needs prior approval and caps the height at 4 metres above ground (see the planning permission guide). Where there is any doubt, a pre-application enquiry to the local authority costs little and de-risks the programme.
From Bay Count to Build: The Quick Method
You can estimate your own site in three steps:
- Count your usable bays — total bays minus the ones you need kept clear (entrance, disabled, columns). Multiply by 0.8 if you are unsure.
- Multiply by 1.7 kWp — that is your indicative canopy capacity.
- Multiply that kWp by 850 — that is your indicative annual kWh.
A 120-bay office car park: 120 × 0.8 = 96 usable bays → 96 × 1.7 = 163 kWp → 163 × 850 = ~139,000 kWh a year. At a blended 25p/kWh saved-and-exported value, that is roughly £35,000 a year before grants or AIA.
That back-of-envelope figure is deliberately conservative — real designs often beat it with bifacial gain and tighter array packing. But it is accurate enough to know whether a canopy is worth a proper feasibility study, and for the vast majority of UK car parks over 30 bays, it is. When you are ready to turn the estimate into engineered numbers, the instant estimate gives an indicative size, cost range, generation and payback straight away, and we reply by email.
For the engineering detail behind those numbers, see our guide to commercial solar carports. The specification and cost bands for single-post canopies are set out in full on our dedicated page.
Related: once you know the size, set it down in a tender specification and check the clearance height against the vehicles that use each bay.