The UK Solar Car Park Mandate: What It Means for Owners

What the government actually announced in May 2025

On 7 May 2025 the Department for Energy Security and Net Zero launched a call for evidence under the banner "Better Deal for Motorists and Businesses with Solar Car Parks." It is important to frame this accurately: it is a government proposal seeking views on whether to mandate solar canopies on new outdoor car parks, not a law that has already taken effect. The consultation ran from 7 May to 18 June 2025 and covers England, Wales and Northern Ireland. The direction of travel echoes countries such as France and Slovenia, where solar on larger car parks is already required in some form. For commercial owners the signal is clear: government wants to turn underused tarmac into clean generation, and a formal requirement for new builds looks like a plausible next step. Acting ahead of any final rule means you can shape your asset on your own timeline rather than to a future compliance deadline.

Who the proposed mandate would affect

The proposal points at new outdoor car parks above a certain size, subject to exemptions still being defined through the consultation. In practice that suggests supermarkets, retail and leisure parks, office campuses, hospitals, universities, distribution hubs, park-and-ride sites and large public-sector estates planning new or substantially redeveloped surface parking. The government's own illustrative example references an 80-space car park, which gives a sense of the scale being discussed, though no final threshold is fixed. Owners and developers with sites in the planning pipeline would be most exposed, because retrofitting a canopy after construction is more disruptive than designing it in. The policy intent also reaches beyond new-build compliance: every commercial car park owner, new or existing, faces broadly the same economics. If your organisation operates surface parking and pays a typical commercial rate of around 45 to 50p per kWh for grid electricity, this proposal is effectively a prompt to review an asset you already own.

The thresholds and exemptions under discussion

The call for evidence deliberately leaves the precise size threshold open, inviting industry input rather than imposing a number. The 80-space example used in the announcement is illustrative, and any eventual cut-off, whether measured in spaces or square metres, would be set after the consultation. A useful technical rule of thumb referenced in the policy discussion is roughly 1 MW of solar capacity per 5,000 m² of car park area, which helps owners estimate generation potential from a site plan. Exemptions are expected to be considered where canopies are impractical: heritage or conservation constraints, structural or ground limitations, heavy shading, grid-connection bottlenecks, or sites earmarked for imminent redevelopment. Because the detail is still being shaped, owners cannot yet treat any single threshold as settled. The safe planning assumption is that larger new outdoor car parks are likely to face a requirement, and that designing for solar readiness now protects you whichever way the final figures land.

The business case: numbers commercial owners should run

The government's illustrative headline is that an 80-space car park could save in the region of £28,000 a year on electricity bills via solar carports. Typical industry figures let owners sketch a project of their own. Commercial solar carports usually cost around £950 to £1,300 per kWp installed, with roughly 1.5 kWp per parking bay. On that basis a 200-bay scheme is approximately 300 kWp, landing somewhere around £285k to £390k turnkey. Annual savings depend heavily on how much generation you use on site versus export, but at a typical 45 to 50p/kWh import rate a scheme of that size can deliver a simple payback in the region of 4 to 7 years, often shorter once the Annual Investment Allowance is applied. Bifacial panels may add an estimated 5 to 12% yield depending on layout and surface. These are typical, estimated figures rather than guarantees, but they show why the policy is framed as a "better deal": a well-sized asset can largely pay for itself well before the panels reach end of life.

Why existing car parks benefit, not just new builds

A common misreading of the proposal is that it would only matter for new car parks. Any mandate may apply to new builds, but the economics apply to any surface car park you already operate. The same canopy that would satisfy a future requirement also shelters customers and stock from the weather, cuts your exposure to volatile grid prices, and can host EV charging that generates parking revenue. Retrofitting a solar carport onto an existing car park is well-established work. Full planning permission is generally required under the Town and Country Planning Act 1990, determined by the local council, and a straightforward application is often decided within roughly 8 to 12 weeks, though timescales vary by authority and site. For existing owners the strategic logic is to move before a mandate arrives, capturing today's grants and tax reliefs and avoiding any future rush on installers and equipment. The policy simply confirms that the value already sitting in your tarmac is real.

Funding, grants and tax reliefs to use now

Several mechanisms can materially shorten payback, and most reward early movers. The Annual Investment Allowance offers 100% first-year tax relief on qualifying plant up to £1m, which is what can compress a 4 to 7 year payback for many commercial schemes. Public-sector owners may be able to access the Public Sector Decarbonisation Scheme, which has funded up to 100% of eligible costs for in-scope bodies in England, alongside Salix finance. Where the scheme includes EV charging, the OZEV Workplace Charging Scheme contributes a set amount per socket (currently £350 per socket, up to 40 sockets), subject to eligibility. Designing in EV-ready DC provision at build avoids costly trenching later and lets you add chargepoints as demand grows from a single grid connection. Combining a grant or relief with the generation savings is what turns a capital project into a clear financial case, and these incentives are best secured early, before any mandate increases demand. Scheme rules change, so confirm current eligibility before you commit.

How to prepare your site step by step

Start with a desktop assessment: measure usable car park area, apply the 1 MW per 5,000 m² rule of thumb and the roughly 1.5 kWp-per-bay figure to estimate capacity and output, then model savings against your current 45 to 50p/kWh tariff. Next, commission a structural and ground survey, a shading study and an early DNO grid-connection enquiry, since connection capacity often shapes project timing more than planning does. Specify MCS-certified, NICEIC-approved installation, design canopies with EV-ready DC provision, and consider bifacial panels for the estimated 5 to 12% yield uplift. Build in the typical 8 to 12 week planning window and assemble your funding stack (AIA, plus PSDS or Salix for eligible public bodies, plus OZEV for charging) before you commit. Whether your site is a new development that could be caught by the proposed mandate or an existing car park chasing the savings, the preparation is the same. To scope your specific car park and get an indicative figure, request a quote at /quote/.