Capital allowances for manufacturer solar, explained

It is one of the most common questions a finance director asks about a solar project, and one of the most commonly got wrong by installers: does the array qualify for full expensing? The short answer is no — solar does not qualify, because it is special-rate plant and machinery and is excluded from that regime. Getting this right matters, because the tax relief is a real part of the return.

Why solar sits in the special-rate pool

The full-expensing regime and the associated 50 percent first-year allowance apply to main-rate and special-rate plant and machinery in specific ways, but solar PV falls into the special-rate pool and is excluded from it. An installer who tells you solar qualifies for a 40 or 50 percent first-year deduction is misreading the rules, and building a business case on that basis will overstate your return.

What actually applies: the Annual Investment Allowance

The route that does apply is the Annual Investment Allowance (AIA). The AIA lets a business deduct 100 percent of qualifying plant and machinery spend, up to £1m a year, from its taxable profits in the year of purchase. Solar PV qualifies, so for the overwhelming majority of manufacturing installs, which sit comfortably under the £1m cap, the whole cost is expensed in year one. For a company paying corporation tax, that is worth up to roughly 25 percent effective relief on the capital in the first year.

Where a project exceeds the £1m AIA cap, the balance goes into the special-rate pool and is written down at the special rate over subsequent years. The exact treatment of spend above the cap depends on prevailing policy, so confirm it with your accountant rather than assuming.

How the relief changes the payback

Because the AIA brings the tax relief forward into year one, it shortens the effective payback. On a typical manufacturing array the headline simple payback of 5 to 7 years improves once you fold in the year-one allowance, and it is one reason ownership routes (outright purchase and asset finance) can beat a PPA on lifetime return: under a PPA you do not own the asset, so the allowance is not yours to claim.

Other funding worth knowing

Beyond capital allowances, energy-intensive manufacturers may hold a Climate Change Agreement, under which on-site generation improves performance against the efficiency target while cutting the Climate Change Levy on every self-consumed unit. The Industrial Energy Transformation Fund offers grants for eligible sites in periodic competition windows, and the Smart Export Guarantee pays for any surplus you export. We map the right combination for your business and, importantly, always point you to current government guidance rather than quoting fixed figures that change with policy.

None of this is tax advice — your accountant signs off the treatment — but it is the framework we build every manufacturer’s model on. See the grants and funding page for more, compare the funding routes, or request a modelled feasibility study for your site.