The tax treatment of a solar carport is more interesting than the sales material suggests, and getting it wrong in a business case is easy because two of the commonest claims — “100% first-year relief” and “Enhanced Capital Allowances” — are both wrong, one because of what solar is and one because the scheme no longer exists.
This is the tax companion to our main page on commercial solar carport cost. It is general information, not tax advice: the split it describes is exactly the sort of thing to settle with your own adviser before the contract is signed, because the contract wording affects the answer.
Solar panels are special rate expenditure — by statute
This is not a matter of interpretation. Section 104A of the Capital Allowances Act 2001 defines “special rate expenditure”, and subsection (1)(g) lists expenditure on the provision of solar panels, with effect from 1 April 2012 for corporation tax and 6 April 2012 for income tax.
That single provision drives most of the consequences:
- No full expensing. Full expensing is a 100% first-year allowance for main rate plant and machinery. Solar panels are special rate, so they are outside it. Any model showing 100% first-year relief on a multi-million-pound solar canopy is wrong on the face of the statute.
- A 50% first-year allowance instead, for special rate expenditure, on qualifying spend that is not covered by the Annual Investment Allowance.
- The Annual Investment Allowance still applies, and it covers special rate expenditure: 100% relief on the first £1 million of qualifying expenditure in the chargeable period. For a scheme comfortably under £1m, AIA is usually the whole story and the distinction above never bites.
- The balance goes into the special rate pool, written down at the special rate rather than the main rate.
So the accurate headline for most commercial canopies is: AIA on the first £1 million, then a 50% first-year allowance on the rest, with the remainder in the special rate pool. Not full expensing.
Enhanced Capital Allowances do not exist any more
They are still quoted constantly, often with a confident “25% tax saving” attached. The Enhanced Capital Allowance scheme for energy-saving and water-efficient plant — the Energy Technology List regime — was abolished from April 2020. If a supplier’s business case cites ECAs, it has not been updated in six years, which is worth knowing about the rest of the document too.
The genuinely open question: is the frame plant or a structure?
Here is where a carport differs from a rooftop array, and where the published guidance runs out.
Plant and machinery allowances are not available for expenditure on a building or on a structure — sections 21 and 22 of the Capital Allowances Act 2001 — unless the item is saved by one of the exceptions in List C at section 23. The classic test is whether the item is apparatus with which the trade is carried on, or merely the setting in which it is carried on.
For a rooftop system the question barely arises: the roof is the building, the panels are plant, and the line is obvious. For a carport it is not obvious at all. The panels, inverters, cabling and any storage are plant. But the canopy itself is a substantial steel structure on engineered foundations — and a reasonable person could argue it either way:
- As plant: the frame exists solely to hold generating equipment at the right pitch and orientation. It is not a building, has no walls, encloses nothing, and would be pointless without the apparatus it carries.
- As a structure: it is a large, permanent, engineered construction fixed to the ground, providing shelter for vehicles — which is a function in its own right, and one that sites value independently of the generation.
Where the frame falls matters because the reliefs are very different in shape. Plant qualifying for AIA gives relief now; expenditure on a structure that does not qualify as plant may instead fall to the Structures and Buildings Allowance, which is a flat 3% a year — relief over 33⅓ years rather than immediately. On a large canopy that is a material cash-flow difference, and it is decided by analysis of the facts rather than by anything a supplier can promise you.
Note how closely this mirrors the business rates position. There, qualifying renewable generation plant is excepted from rating valuations until 31 March 2035, but the land and settings stay rateable, above about 50 kW the supports and settings are valued — and no legislation or valuation guidance addresses whether a car park canopy’s steel frame is rateable. Two different regimes, the same unresolved boundary, running through the same piece of steel. Our solar canopy business rates page sets out the rating side in detail.
What follows practically
Separate the contract lines. Foundations, structure, generation plant, electrical works and EV charging equipment as distinct items with distinct values. If everything arrives as one lump sum for “supply and install solar carport”, the analysis has to be reconstructed after the fact from whatever breakdown you can get, and the weakest position is the one where you cannot evidence the split at all. This is the single most useful thing you can do before signing, and it costs nothing.
Get the plant-versus-structure view early. Before contract, not at the year end. The answer may influence how the scheme is specified and procured.
Do not forget the chargepoints. EV chargepoint plant attracts a 100% first-year allowance to 31 March 2027, which is a genuinely generous and time-limited relief in its own right, separate from anything the solar attracts. If charging is part of the plan, the deadline is a real reason not to phase it to a later year. Our EV charging under a solar canopy page covers the grants and the infrastructure.
Remember who this applies to. Capital allowances need a taxable trade. A local authority, NHS trust, academy trust or charity is not a corporation tax payer, so none of the above helps them — which is part of why the funding question is so much harder for public bodies since the Public Sector Decarbonisation Scheme closed to new applications in November 2024. Current routes are on our solar canopy grants and funding page.
The short version
| Claim | Position |
|---|---|
| ”Full expensing / 100% first-year relief” | Wrong. Solar panels are special rate expenditure under CAA 2001 s.104A(1)(g). |
| ”Enhanced Capital Allowances give 25% back” | The ECA scheme was abolished from April 2020. |
| ”AIA covers it” | Usually yes, up to £1 million of qualifying spend in the period — including special rate expenditure. |
| ”Above £1m you get nothing” | A 50% first-year allowance applies to special rate expenditure, with the balance in the special rate pool. |
| ”The whole carport is plant” | Unsettled. Sections 21–23 exclude structures from plant and machinery allowances, and where a canopy frame sits is a question of fact. |
| ”EV chargers are treated the same as the solar” | No — chargepoint plant has its own 100% first-year allowance to 31 March 2027. |
If you are building the appraisal now, our commercial solar carport cost page sets out the cost drivers in the order they actually matter, and a free feasibility assessment returns indicative capacity, modelled generation and the consent position within five working days.