Annual Investment Allowance: Still 100% Up to £1 Million
AIA Status: Confirmed for 2026-27
The Annual Investment Allowance (AIA) remains at £1 million per annum for the 2026-27 tax year, as confirmed in the Spring 2026 Budget. Solar panels installed on UK commercial and industrial premises qualify as plant and machinery and are eligible for 100% first-year tax deduction under AIA.
The AIA allows qualifying businesses to deduct the full cost of plant and machinery investments from their taxable profits in the year of purchase, rather than spreading the deduction over multiple years under the standard writing-down allowance (WDA) approach. For a solar installation costing £300,000 and a business paying 25% corporation tax, the AIA saves £75,000 in tax in the first year — reducing the effective cost of the installation to £225,000.
Key AIA Rules for Factory Solar
| Rule | Detail |
|---|---|
| Annual limit | £1,000,000 per annum (confirmed for 2026-27) |
| Eligible entities | UK companies, partnerships, sole traders — most commercial businesses qualify |
| Solar panels eligible? | Yes — panels, inverters, mounting, cabling, monitoring systems all qualify as plant and machinery |
| Timing | Deduction taken in the tax year in which expenditure is incurred (typically the year installation is completed) |
| Tax saving (25% CT rate) | 25% of eligible expenditure; a £200,000 installation saves £50,000 in corporation tax |
| Planning consideration | If multiple capital investments are planned, consider staging to maximise AIA use in each tax year |
Note: The AIA is a UK government tax relief. Always confirm eligibility and optimal timing with your accountant or tax adviser. This article provides general information only and is not tax advice.
IETF Phase 4: Applications Open
IETF Phase 4 Application Window: Open Spring 2026
The Industrial Energy Transformation Fund (IETF) Phase 4 application window is currently open as of April 2026. Eligible manufacturers can apply for capital grants of up to 50% of eligible project costs for energy efficiency and decarbonisation projects. Application deadline to be confirmed — check DESNZ for current guidance.
The IETF is the UK government's primary capital grant programme for energy-intensive manufacturing businesses seeking to reduce their energy consumption and carbon emissions. Phase 4 continues the programme structure established in earlier phases, with grants available for qualifying capital projects including solar PV installation.
IETF Phase 4 Eligibility Criteria
- Energy-intensive manufacturer — IETF is targeted at businesses where energy costs represent a significant proportion of total production costs. There is no fixed threshold, but applicants must demonstrate energy-intensive activity.
- UK-based manufacturing — the funded project must be at a UK manufacturing facility. The business must be trading in the UK and intend to continue doing so for at least the grant term.
- Minimum project size — Phase 4 typically requires a minimum eligible project cost of £100,000 to qualify for a grant. Projects below this threshold are unlikely to meet the administrative cost-benefit threshold for IETF.
- Additionality — the IETF requires that the grant is necessary for the project to proceed on the planned timeline. Projects that would proceed anyway without the grant are unlikely to score well on additionality criteria.
- State aid compliance — IETF grants are provided under the UK Subsidy Control Act 2022. Businesses that have received other public subsidies may have cumulative limits to manage.
Grant Percentages and Eligible Activities
| Activity Type | Max Grant % | Example |
|---|---|---|
| Energy efficiency improvement | Up to 30% | LED replacement, compressed air efficiency, heat recovery |
| Deep decarbonisation technology | Up to 50% | Solar PV, electrification of heat processes, hydrogen-ready equipment |
| Feasibility studies | Up to 50% | Detailed energy audits, decarbonisation roadmap development |
Solar PV is specifically listed as an eligible activity under Phase 4's deep decarbonisation technology category, qualifying for up to 50% grant funding. For a £300,000 solar installation, a successful IETF Phase 4 application could contribute up to £150,000 in grant funding — dramatically improving the financial case and potentially halving the payback period.
The IETF is competitive and oversubscribed. It is strongly advisable to engage an experienced IETF grant consultant to prepare your application — success rates for professionally prepared applications are significantly higher than self-prepared submissions. Allow 8–16 weeks from application to grant decision.
ESOS Phase 4: December 2027 Deadline Approaching
ESOS Phase 4 Compliance Deadline: 5 December 2027
UK businesses that qualify for ESOS (Energy Savings Opportunity Scheme) must complete their Phase 4 energy audit and submit their compliance notification to the Environment Agency by 5 December 2027. With only 20 months remaining, businesses should be engaging ESOS Lead Assessors and beginning their audit process now.
Who Qualifies for ESOS Phase 4?
An organisation qualifies for ESOS if it meets any of the following criteria:
- Has 250 or more employees; or
- Has an annual turnover exceeding £44 million AND a balance sheet exceeding £38 million; or
- Is a UK subsidiary of a qualifying company within a corporate group
How Solar Satisfies ESOS Obligations
ESOS requires qualifying organisations to conduct audits of their energy use and identify energy saving opportunities — it does not mandate implementation. However, Phase 4 introduced a "Significant Energy Savings Opportunities" requirement: businesses must identify and explain in their ESOS report at least one significant energy saving opportunity, or explain why none exist.
Businesses that have already installed solar panels can reference the solar installation as evidence of energy saving action taken. The ESOS report should include: total generation data from the solar monitoring system; the kWh displaced from grid electricity; the associated CO2 reduction; and the financial saving achieved. This demonstrates compliance with the spirit of ESOS — identifying and implementing energy savings — and typically satisfies ESOS Lead Assessors reviewing the submission.
For more detail on ESOS compliance, see our dedicated guide: ESOS Phase 4 Solar Compliance Guide.
Smart Export Guarantee: Current Rates Spring 2026
The Smart Export Guarantee (SEG) requires licensed electricity suppliers with over 150,000 domestic customers to offer export tariffs to eligible small-scale generators. For commercial and industrial systems, the process and rates differ from domestic SEG applications.
| Supplier | Tariff Name | Rate (Spring 2026) | Commercial Availability |
|---|---|---|---|
| Octopus Energy | Outgoing Octopus | 5.0–6.0p/kWh | Yes — commercial systems up to 5MW eligible; contact for large systems |
| E.ON Next | Export Exclusive | 4.0–5.0p/kWh | Available; rates for large commercial may be individually negotiated |
| British Gas | Solar Export | 3.5–4.5p/kWh | Available; commercial applications processed separately |
| EDF Energy | Export tariff | 3.5–5.0p/kWh | Available; large commercial negotiated individually |
| Scottish Power | Export tariff | 3.0–4.0p/kWh | Available; contact commercial team for large systems |
Note: SEG rates change frequently. The figures above are indicative for Spring 2026 based on published tariff data. Always check current rates directly with your electricity supplier. For systems over 50kW (G99 applications), commercial SEG arrangements may differ from published domestic rates.
G99 and SEG: Important Note
Factory solar systems over 50kW require a G99 grid connection agreement with your DNO. You must have a G99 Agreement in place before you can register for SEG export payments. Most SEG suppliers require a copy of your G99 Agreement and an MCS certificate (or equivalent) as part of the registration process.
EPC Band C Deadline: April 2027 for New Commercial Leases
Action Required: April 2027 Deadline
From April 2027, it will be unlawful for landlords in England and Wales to let commercial property on a new lease if the building has an EPC rating below Band C. Buildings currently at Band D or below must be improved before they can be marketed for new leases.
The Minimum Energy Efficiency Standards (MEES) for commercial buildings are being progressively tightened. The current minimum for new commercial leases is EPC Band E. From April 2027, this rises to Band C — a significant step up that affects a large proportion of older UK commercial and industrial properties.
How Solar Contributes to EPC Improvement
EPC ratings for commercial buildings are calculated using the Simplified Building Energy Model (SBEM), which assesses the building's estimated energy performance. Solar panels reduce the building's estimated net energy consumption by generating electricity on-site, which improves the EPC score.
The EPC improvement from solar varies by building type, size and existing rating, but in general:
- A building at Band D may improve to Band C with a solar system sized to offset 30–40% of annual energy use.
- A building at Band E typically requires solar plus one or two other measures (LED lighting, roof insulation) to reach Band C.
- A new EPC must be produced after solar installation to reflect the improvement — your installer should be able to advise on whether a new assessment is needed.
For commercial landlords with industrial tenants, the April 2027 deadline is 12 months away. Commissioning an EPC assessment now, followed by solar installation (total project timeline typically 4–6 months), leaves a comfortable margin before the deadline.
UK ETS Carbon Price: Implications for Energy-Intensive Manufacturers
The UK Emissions Trading Scheme (UK ETS) is a cap-and-trade carbon pricing mechanism that applies to large energy-intensive installations, including power stations and certain manufacturing processes. The UK ETS carbon price in Spring 2026 is approximately £38–45/tonne CO2.
Most factory solar decisions are not directly driven by the UK ETS, as the scheme applies to electricity generators rather than electricity consumers. However, the UK ETS has two indirect effects on factory solar economics:
1. ETS Adds to Electricity Prices
Gas-fired power stations pay UK ETS allowances on their CO2 emissions. These costs are passed through to electricity buyers in the wholesale market. At £40/tonne CO2 and a gas plant efficiency of approximately 50%, the UK ETS adds approximately 1.5–2p/kWh to wholesale electricity prices. This contributes to the elevated electricity prices that make solar attractive.
2. CBAM Applies to Certain EU-Exported Products
The EU Carbon Border Adjustment Mechanism (CBAM) applies to steel, aluminium, cement, fertilisers, electricity and hydrogen exported to the EU. From 2026, exporters of these products to the EU must pay a CBAM charge reflecting the carbon intensity of production. Reducing the Scope 2 carbon intensity of production (through solar) directly reduces CBAM liability for affected manufacturers. For steel fabricators and aluminium processors exporting to the EU, this is an increasingly material financial consideration.
DNO Connection Timelines: Regional Update Spring 2026
G99 grid connection applications — required for factory solar systems over 50kW — are processed by the relevant Distribution Network Operator (DNO). Processing times have improved modestly compared to 2024 peak congestion, but remain variable by region. The following table shows current (Spring 2026) indicative G99 processing timelines.
| DNO | Region | Typical G99 Processing Time | Comments |
|---|---|---|---|
| National Grid / UK Power Networks | South East, East Anglia | 14–20 weeks | High constraint area; network reinforcement more common |
| Western Power Distribution (now National Grid) | South West, Midlands, South Wales | 8–14 weeks | Improving; Bristol area longer than average |
| Northern Powergrid | North East England, Yorkshire | 8–12 weeks | Generally improving; some congestion in Teesside industrial areas |
| Electricity North West | North West England | 10–16 weeks | Greater Manchester industrial zones seeing longer waits |
| SP Energy Networks | Scotland, North Wales | 10–18 weeks | Variable by area; rural areas often longer |
Tips for Accelerating G99 Applications
- Submit early: The G99 application clock only starts when the DNO accepts your application. Submit as early as possible in the project — ideally immediately after the site survey is completed, before finalising panel count and inverter selection.
- Use a specialist installer: Experienced installers know the DNO application process, can prepare technically accurate submissions first time, and have established relationships with DNO connection engineers. Poor-quality applications are returned with queries, adding weeks to processing time.
- Have your site electrical details ready: DNO applications require details of your existing electrical infrastructure, main switch fuse (MSF) rating, and existing metering arrangement. Gather these before submitting.
- Budget for reinforcement: Ask your installer to check network headroom at your site before committing to a project. If headroom is tight, factor in potential reinforcement costs and delays from the outset.
Net Zero Supply Chain Requirements: Automotive Sector Update
The UK automotive sector's supply chain sustainability requirements have accelerated materially in 2025–2026, driven by OEM commitments to Net Zero supply chains and the EU's Corporate Sustainability Reporting Directive (CSRD) — which requires European vehicle manufacturers to report Scope 3 emissions from UK suppliers.
JLR (Jaguar Land Rover) Supplier Requirements
JLR has committed to reaching net zero across its entire supply chain by 2039. From 2026, JLR's supplier questionnaires now require Tier 1 and selected Tier 2 suppliers to provide verified Scope 1 and Scope 2 emissions data, and to demonstrate a credible decarbonisation plan. Solar PV installation — with verified generation data — directly satisfies the Scope 2 evidence requirement and demonstrates active decarbonisation action.
Nissan Manufacturing UK Supply Chain
Nissan's Sunderland plant (producing the Nissan Leaf and Ariya) has committed to operating on 100% renewable electricity by 2028, and is extending this requirement to key Tier 1 suppliers from 2027. Suppliers are being asked to demonstrate renewable electricity use through one of three mechanisms: direct solar generation, renewable energy certificates (RECs), or a green electricity tariff. On-site solar generation is the most commercially attractive and evidentially robust of these options.
Toyota UK Supply Chain
Toyota's Burnaston and Deeside plants have issued supplier sustainability guidance requiring Tier 1 suppliers to have completed a carbon footprint assessment and identified their largest emission sources by December 2026. Suppliers with purchased electricity as a significant Scope 2 source are being encouraged to invest in on-site renewable generation. Solar PV is specifically cited in Toyota's supplier guidance as a preferred route to Scope 2 reduction.
For UK automotive suppliers, the combination of supply chain requirements from multiple OEMs and the financial case for solar on its own merits creates a compelling and multi-dimensional argument for investment. The supply chain compliance value of solar can be quantified in terms of contract retention and preferred supplier status — factors that can dwarf the electricity savings in commercial significance.