Full Expensing for Warehouse Solar: How to Claim 100% First-Year Tax Relief

Full Expensing is a 100% first-year capital allowance for main rate plant and machinery. Solar panels, inverters, mounting systems, cabling, meters, and monitoring equipment all qualify as plant and machinery, making the full cost of a solar installation eligible for a 100% deduction against corporation tax in the year of purchase.

Unlike the Annual Investment Allowance (AIA), which has a £1 million annual cap, Full Expensing has no upper limit. A company installing a £5 million rooftop solar system on a large distribution centre can deduct the entire cost in year one — a tax saving of £1.25 million at the current 25% corporation tax rate.

Full Expensing applies to UK incorporated companies paying corporation tax. Sole traders and partnerships use the equivalent Capital Allowances regime (Annual Investment Allowance). The timing rule is that expenditure must be incurred in the accounting period for the claim to be made — so timing your installation relative to your financial year-end matters.

The practical implication for warehouse operators is significant: a £200,000 solar installation generates a £50,000 corporation tax saving in year one. The effective cost of the installation is not £200,000 but £150,000. This fundamentally changes the payback calculation and makes solar investment rational even for businesses with higher costs of capital.

A profitable UK logistics company installs a 400kW rooftop solar system at total cost of £310,000. Corporation tax rate: 25%. Annual electricity savings at 27p/kWh with 80% self-consumption: £83,592. Annual SEG export income: £6,200. Total annual benefit: £89,792.

Year one tax relief under Full Expensing: 25% × £310,000 = £77,500. Effective installation cost after tax: £232,500. Simple payback at £89,792/year: 2.59 years.

Without any tax relief: payback is £310,000 ÷ £89,792 = 3.45 years. Full Expensing saves 10 months off the payback period and increases the 25-year IRR from approximately 26% to 32%.

If the company also secures a regional UKSPF grant of £50,000, effective cost drops to £182,500 and payback to 2.03 years — one of the strongest commercial investment returns available in the UK market.

Warehouse landlords who install solar and supply electricity to tenants face a different tax treatment. The AIA does not apply to plant hired or leased to others. However, equipment used in the landlord's own business — for instance, solar powering common areas, landlord-controlled lighting, or vacant unit services — does qualify.

Landlords can structure solar supply arrangements to maximise tax efficiency. One approach is a direct sale arrangement where the landlord supplies electricity to the tenant as a service charge item — in some tax interpretations, this preserves AIA eligibility. Specialist property tax advice is essential for any landlord solar project.

Under a PPA airspace lease model where a third-party investor owns the solar system, the landlord has no capital allowances to claim but also no capital outlay. The tax treatment is clean: any rooftop lease income received is taxable business income, and any sub-metered electricity supply income is also taxable.

For landlords structured as REITs, capital expenditure on solar improvements to let properties is treated as allowable expenditure against REIT profits. The combination of improved EPC rating, rental premium potential, and tax efficiency makes solar a compelling REIT investment particularly ahead of 2030 MEES compliance deadlines.