Capital Allowances for Commercial Solar Panels
Quick Answer
How does HMRC treat solar panels for capital allowances?
HMRC treats a commercial solar PV system as plant and machinery under the Capital Allowances Act 2001 (CAA 2001), so the whole installed cost qualifies for capital allowances. The panels, inverters, mounting and cabling are dealt with in HMRC's Capital Allowances Manual at CA21010 onwards, and battery storage at CA23130. Because solar is treated as plant rather than as part of the building, it sits outside the integral features 6% special-rate pool — so you can claim 100% via the Annual Investment Allowance (AIA) or Full Expensing in year one rather than writing it down slowly.
Claim capital allowances on commercial solar panels. AIA 100% deduction, full expensing, writing down allowances. Worked examples and tax savings guide.
UK businesses can claim substantial tax relief on commercial solar installations through capital allowances. Understand how AIA, full expensing, and writing down allowances reduce your effective cost and accelerate payback.
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AIA Relief
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AIA Limit
Understanding Capital Allowances for Solar
Capital allowances are a form of tax relief that allows businesses to deduct the cost of certain capital assets from their taxable profits. Commercial solar panel installations qualify as plant and machinery, making them eligible for some of the most generous capital allowance provisions available to UK businesses in 2026.
The tax relief available can significantly reduce the effective cost of a commercial solar installation. At the current corporation tax rate of 25%, a business investing £100,000 in solar panels can reduce its tax bill by £25,000 in the year of installation alone. For sole traders and partners paying the higher income tax rate of 40%, the same investment yields £40,000 in tax relief.
Understanding which capital allowance mechanism to use, and how to structure your claim correctly, is essential to maximising this benefit. The UK tax system provides four main routes to capital allowance relief for commercial solar installations, each with different rules, limits, and eligibility criteria.
The Annual Investment Allowance (AIA)
The Annual Investment Allowance is the most straightforward and widely used mechanism for claiming tax relief on commercial solar panels. It allows businesses to deduct 100% of qualifying expenditure from taxable profits in the year of purchase, up to an annual limit of £1,000,000. This permanent limit, set at £1M since January 2019, comfortably covers the vast majority of commercial solar installations.
The AIA is available to all UK business structures: sole traders, partnerships, limited liability partnerships, and incorporated companies. The qualifying expenditure includes the solar panels themselves, inverters, mounting and racking systems, cabling and electrical works, battery storage systems, and monitoring equipment. Essentially, the entire installed cost of a commercial solar system qualifies.
One important consideration is the accounting period in which the expenditure falls. The AIA limit is proportional to the length of the accounting period. For a standard 12-month period, the full £1,000,000 limit applies. For shorter periods, the limit is reduced proportionally. Businesses should plan the timing of their solar investment to ensure they can utilise the AIA effectively, particularly if they have other qualifying capital expenditure in the same period.
Full Expensing for Companies
Full expensing was introduced in the Spring Budget 2023 and subsequently made permanent. It provides incorporated companies with a 100% first-year deduction for qualifying main rate plant and machinery, with no monetary limit. This is particularly relevant for large-scale commercial solar installations where the cost exceeds the £1,000,000 AIA threshold.
The critical distinction is eligibility: full expensing is available only to companies subject to corporation tax. Sole traders and partnerships cannot use this route and are limited to the AIA and writing down allowances. For companies investing in solar systems costing more than £1M, full expensing provides the same 100% first-year relief that the AIA offers for smaller investments, ensuring that the scale of the installation does not diminish the tax benefit.
Writing Down Allowances at 18%
Where the AIA has been fully utilised on other expenditure and full expensing is not available (for unincorporated businesses), solar panels can be allocated to the main rate capital allowances pool and written down at 18% per annum on a reducing balance basis. This spreads the tax relief over the useful life of the asset rather than concentrating it in year one.
Under writing down allowances, a £100,000 solar installation would generate £18,000 of relief in year one, £14,760 in year two (18% of the remaining £82,000), and so on. Over 10 years, approximately 86% of the cost would have been relieved. While slower than the AIA or full expensing, writing down allowances still provide meaningful tax benefits and may be the appropriate route for businesses with complex capital expenditure profiles.
Enhanced Capital Allowances for Energy-Efficient Technology
The Enhanced Capital Allowances (ECA) scheme specifically targets energy-efficient and environmentally beneficial equipment. Solar photovoltaic panels and associated equipment listed on the government's Energy Technology List (ETL) qualify for 100% first-year allowances under the ECA scheme, regardless of the AIA position.
The ETL is maintained by the Department for Energy Security and Net Zero and is updated periodically. To qualify for ECAs, the specific products used in your installation must appear on the current version of the list at the date of expenditure. Your solar installer should be able to confirm whether the proposed equipment qualifies. ECAs provide a valuable alternative route to 100% first-year relief, particularly useful for businesses that have already used their AIA on other qualifying expenditure.
Interaction with Corporation Tax
The value of capital allowances is directly linked to your effective tax rate. Since April 2023, the main rate of UK corporation tax has been 25% for companies with profits above £250,000. The small profits rate of 19% applies to companies with profits below £50,000, with marginal relief for profits between these thresholds.
This means that for most commercial solar installations, each £1,000 of qualifying expenditure reduces the tax bill by £250 at the main rate, or £190 at the small profits rate. Sole traders and partners benefit at their marginal income tax rate: 20% for basic rate taxpayers, 40% for higher rate, and 45% for additional rate taxpayers. Higher-rate taxpayers therefore receive proportionally greater tax benefit from capital allowances on solar installations.
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Related Resources
Capital Allowance Types at a Glance
Four routes to tax relief on commercial solar installations, each suited to different business circumstances.
Eligibility:
Worked Examples: Tax Savings by System Size
These examples illustrate the impact of capital allowances on the effective cost and payback period of commercial solar installations at different scales.
System Size
Based on 25% corporation tax rate, 30p/kWh electricity cost, and typical self-consumption ratios. Actual results vary by location and usage patterns.
How to Claim Capital Allowances
Follow these steps to ensure your business claims the maximum available tax relief on your commercial solar installation.
Capital Allowances FAQs
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Every quotation we produce includes a detailed capital allowances breakdown showing the tax savings available for your specific business structure and tax position. Our team works alongside your accountant to ensure you claim every penny of relief available.
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Frequently Asked Questions
Can I claim AIA on commercial solar panels?
Yes. Commercial solar panels qualify for Annual Investment Allowance (AIA), allowing 100% of the installation cost to be deducted from taxable profits in the year of purchase. The AIA annual limit is £1 million — sufficient to cover virtually all commercial solar projects. AIA applies to both outright purchase and hire purchase (asset finance where you own the asset during the term). It does not apply to operating leases or Power Purchase Agreements.
What is the Annual Investment Allowance limit for solar in 2026?
The AIA limit is £1 million per tax year (2026). This means you can deduct up to £1 million of qualifying plant and machinery — including commercial solar panels, inverters, battery storage, and mounting systems — in a single tax year. For most commercial solar projects (typically £38,000–£750,000), the full installation cost falls within the AIA limit, making 100% first-year relief available.
Can I claim capital allowances on solar battery storage?
Battery storage systems installed alongside commercial solar panels qualify for AIA as plant and machinery. Battery storage installed without solar panels also qualifies for AIA. Commercial battery energy storage systems (BESS) at any scale — from 10kWh to multi-MWh — are treated as qualifying plant and machinery under CA23130 (HMRC Capital Allowances manual). Rate: 100% AIA or 50% Full Expensing in the year of purchase.
What is Full Expensing for commercial solar?
Full Expensing (FE) is an alternative to AIA introduced from April 2023, providing a 100% first-year deduction for qualifying plant and machinery for incorporated companies. Unlike AIA, there is no annual cap on Full Expensing. However, FE only applies to companies (not sole traders or partnerships), and only to new equipment. Solar panels bought second-hand do not qualify for FE. For most businesses, AIA and FE produce the same tax outcome — use whichever your accountant recommends.
What happens to capital allowances if I sell the solar panels?
If you sell solar panels that you claimed AIA or Full Expensing on, a balancing charge arises in the year of disposal. The disposal proceeds (sale value) are added back to your taxable profits. For most commercial solar installations, the panels are retained for their 25-year lifespan rather than sold, so this rarely arises in practice. If the site is sold with solar panels in place, the value attributed to the panels in the property valuation affects the calculation.
Solar Capital Allowances and HMRC: How the Claim Actually Works
The reason commercial solar attracts such generous relief is the way HMRC classifies it. Under the Capital Allowances Act 2001 (CAA 2001), a rooftop or ground-mounted PV array installed to power a trade is plant and machinery — not part of the building fabric. HMRC's own Capital Allowances Manual confirms this: general plant qualifies from CA21010, and battery energy storage is dealt with at CA23130. This classification is what unlocks the 100% Annual Investment Allowance (AIA), because solar is not caught by the slow-relief "integral features" rules that apply to lighting, heating and general electrical systems.
The phrase businesses search for — "solar panels capital allowances HMRC" — usually means one of two practical questions: does it qualify, and where do I claim it. On qualification, the full installed cost is allowable: modules, inverters, optimisers, mounting and racking, DC and AC cabling, the G99/G98 connection works, scaffolding and commissioning. On the claim itself, a limited company enters the expenditure in its capital allowances computation and carries the figure into box 690+ of the CT600 corporation tax return; sole traders and partnerships claim through the capital allowances pages of the Self Assessment return. The claim is made for the accounting period in which the asset is brought into use, which for solar is the commissioning/energisation date.
- "solar panels AIA": AIA gives 100% relief up to £1,000,000 per 12-month period — a £100,000 (≈100kWp) system at £0.75–£1.05/W is fully relieved in year one, cutting a 25% corporation-tax bill by £25,000.
- Full Expensing: companies with spend above the AIA cap get the same 100% first-year deduction with no limit — useful for multi-MW rooftops.
- What HMRC will not allow: 100% relief on PPA or operating-lease systems you don't own, and Full Expensing on second-hand panels (AIA still applies to used kit).
Frequently Asked Questions
What is the HMRC capital allowances manual reference for solar panels?
Can I claim AIA on solar panels?
Where do I claim solar capital allowances on my tax return?
Do solar panels count as integral features for HMRC?
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