UK Tax Relief for Warehouse Solar: Worked Examples and Planning

The UK tax relief stack for warehouse solar — 100% Annual Investment Allowance, 50% First Year Allowance, and Freeport Enhanced Capital Allowance — can reduce effective net cash cost by 25-50% versus headline capex. This guide works through realistic examples at different project scales and shows how multi-year capex sequencing and group company structures can maximise the total allowance captured.

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Single-site owner-occupier: £900k install

Qualifying plant and machinery capex: £870k (panels, inverters, mounting, cabling, monitoring, switchgear). Structural reinforcement: £30k (integral features, 6% WDA). AIA on £870k P&M: £217,500 year-one tax shield (at 25% corp tax). After-tax net cash cost: £652,500. Net cash payback: 3.0 years. 25-year IRR: 24.7%.

Multi-site tenant: £2.4m portfolio rollout

3 sites across 2 tax years. Year 1: £1m AIA = £250k tax shield; £200k FYA on £400k residual = £50k shield; total year-1 shield £300k. Year 2: £1m AIA on second tranche = £250k shield. Total allowance captured: £550k over 2 years. Effective net cost of £1.85m on £2.4m headline capex.

Freeport zone: £2.5m at Felixstowe (Freeport East)

100% Enhanced Capital Allowance on P&M in addition to standard AIA. Year-1 calculation: £1m AIA = £250k. £1.5m residual at 100% ECA = £375k. Total year-1 tax shield: £625k. Net cash cost: £1.875m. After-tax cash payback: 2.9 years. 25-year IRR: 28%. Note: ECA does not stack additively with AIA — apply AIA first, then ECA on residual qualifying P&M within the Freeport zone.

Multi-year sequencing for portfolio rollouts

AIA is £1m per company per tax year. For a 10-site portfolio with £750k per site (£7.5m total), rolling out 1-2 sites per tax year preserves £1m AIA per year. A £7.5m portfolio split over 8 tax years captures £7.5m of AIA (100% coverage) versus a single-year rollout that would capture only £1m AIA + £3.25m FYA (46% first-year shield on residual). Sequencing adds approximately £1.5m in NPV on a portfolio of this scale. Group companies share one AIA — cross-company allocation must be documented.

Common questions

Can we claim AIA every year on new solar installs?

Yes, up to £1m per limited company per tax year. Each new qualifying installation in a new tax year gets the full AIA allocation. For multi-site rollouts, sequencing capex across years maximises total AIA captured — each year of commissioning starts a new AIA allowance.

How do group companies handle AIA allocation?

Group companies share a single £1m AIA allowance. The allocation between group members must be documented and agreed before the corporation tax return is filed. Common approach: allocate full £1m to whichever group entity commissions the largest project in that tax year.

What is the Freeport ECA deadline?

Freeport Enhanced Capital Allowance is currently legislated to 30 September 2031. Check the published Freeport zone map for specific site eligibility — geographic boundaries are precise and do not always match the named city or port. Site-specific eligibility check is essential before factoring ECA into project economics.