Solar Panels for Farms and Agricultural Buildings UK

Rising electricity bills have pushed farm energy to the top of the business-planning agenda. A typical UK dairy producing 2.5 million litres a year spends between £15,000 and £35,000 on electricity alone — and that figure climbs steeply for arable enterprises running continuous grain dryers or refrigerated packing lines. Solar PV has become one of the most straightforward ways to cut that exposure: a well-sized roof array can offset 40–70% of daytime electricity use and produce a return on investment within five to seven years, often less once grants and tax relief are factored in.

Planning rules: what you can install without full permission

Roof-mounted solar on agricultural buildings is covered by Class J (and the related Class J(c) prior-approval route) of Schedule 2, Part 14 of the Town and Country Planning (General Permitted Development) (England) Order 2015. Under permitted development, panels on a non-domestic roof must not protrude more than 200 mm beyond the plane of the roof slope, must sit at least 1 metre from the roof's external edge, and must not exceed the highest point of the roof. There is no explicit kilowatt cap for roof-mounted systems on commercial and agricultural buildings under Class J, meaning a 250 kWp barn roof array can proceed without a planning application — provided all physical conditions are met.

Stand-alone (ground-mounted) arrays require full planning permission from the local planning authority (LPA) in almost all practical cases. Ground-mounted solar on agricultural land falls outside the standard domestic or commercial permitted development classes. Systems below 50 MW are decided by the LPA; those above 100 MW are Nationally Significant Infrastructure Projects requiring a Development Consent Order from the Secretary of State. Since December 2025, projects between 50 MW and 100 MW use the faster local planning route rather than the DCO process.

One nuance worth flagging: Class Q permitted development — which converts agricultural buildings into dwellings — removes solar PV permitted development rights from the resulting dwelling. If a building has been converted under Class Q, a separate planning application is needed for any subsequent solar installation.

Scotland, Wales, and Northern Ireland operate their own planning regimes; the rules above apply to England only. Always check with your LPA or a planning consultant before proceeding.

The FETF grant: 25% off eligible solar installations

The Farming Equipment and Technology Fund (FETF), administered by the Rural Payments Agency (RPA) on behalf of Defra, has in recent rounds offered a 25% contribution towards eligible solar PV installations on farm buildings and floating reservoirs — explicitly excluding ground-mounted systems. The FETF 2025 round received approximately 9,500 applications across its three themes, indicating strong demand; watch the Defra Farming Blog and RPA announcements for future rounds.

Grant minimums, maximums, and eligible item lists change each round, so always consult the current GOV.UK guidance rather than relying on figures from previous years. The RPA publishes full item specifications detailing which solar equipment qualifies. Ground-mounted systems have historically been out of scope for FETF — if your project involves a ground array, you will need to rely on capital allowances and Smart Export Guarantee income rather than a direct grant.

Capital allowances: 100% relief in year one

Annual Investment Allowance (AIA) is the most tax-efficient route for farm solar. It allows you to deduct 100% of qualifying capital expenditure — including commercial solar PV systems — against your taxable profits in the year of purchase, up to the current £1,000,000 AIA limit per year. For most farm solar projects (which typically range from £40,000 for a 50 kWp rooftop system to £450,000 for a 500 kWp installation), the full cost falls within this limit and can be written off immediately.

Solar panels are classified as special rate expenditure under the Capital Allowances Act — technically an integral feature — which means they fall into the 6% per annum Writing Down Allowance pool if AIA is not available or has already been fully used. The AIA route is therefore strongly preferable for most farming businesses. Consult your accountant to confirm how the relief interacts with your business structure, particularly if you operate through a company rather than as a sole trader or partnership.

Smart Export Guarantee: earning from surplus generation

Any electricity your farm generates but does not use on-site can be exported to the grid under the Smart Export Guarantee (SEG). Mandatory SEG suppliers — energy companies with 150,000 or more domestic customers — must offer at least one export tariff. Best flat-rate SEG tariffs currently reach around 25p/kWh for farm and commercial premises, while time-of-use tariffs can peak higher during demand windows. The SEG covers systems up to 5 MW, well above the scale of any single farm installation.

For agricultural load profiles — daytime milking, continuous grain dryers, refrigeration running around the clock — self-consumption tends to be high, limiting the volume of surplus available to export. Battery storage can shift solar generation into evening or early-morning demand peaks, but the economics need careful modelling; see our guide to home battery storage for the principles, which apply equally to farm battery systems.

Sizing solar for common farm loads

Dairy farms are among the best candidates for solar. A 500-cow herd typically spends £20,000–£50,000 on electricity annually, with load concentrated in milking periods (4 am–8 am and 2 pm–6 pm) and continuous refrigeration. A 100–150 kWp roof array on a parlour or cubicle shed can offset a significant proportion of the parlour's electricity use. Morning milking peaks partially coincide with early generation on summer mornings; winter shortfalls require grid top-up or battery buffering.

Arable farms with grain drying run very high loads over short seasonal windows — a continuous-flow dryer can draw 50–200 kW during harvest. A fixed solar array sized to annual average load will underproduce during harvest and overproduce outside it. In this case, sizing to the off-season baseline load and using SEG income to offset harvest grid bills is often more cost-effective than oversizing to match peak drying demand.

Poultry and pig units with continuous ventilation, heating, and lighting are ideal solar hosts: their load is relatively constant across daylight hours and the buildings typically have large, unshaded south-facing or east–west roof areas suited to large arrays.

System size rules of thumb (2026 costs): installed costs run from roughly £900–£1,100 per kWp for smaller systems (under 50 kWp) to £700–£850 per kWp for larger installations above 250 kWp. A 50 kWp system costs approximately £40,000–£55,000 before grant; a 250 kWp system falls in the £175,000–£215,000 range. After 25% FETF grant (on eligible roof systems) and first-year AIA relief at your marginal tax rate, the net day-one cost can be substantially lower.

Battery storage for agricultural load profiles

Battery systems paired with farm solar make most economic sense when there is a clear time-shift opportunity — typically shifting midday generation into evening livestock operations or early-morning milking. Usable capacities of 100–200 kWh are common on working farms. Batteries do not qualify for FETF but do qualify for the AIA alongside the solar system. For a detailed look at how battery storage works and what to look for in a system, see our solar cost and savings guide, which covers the financial modelling approach.

Key steps before you commit

1. Commission a farm energy audit. AHDB guidance recommends understanding your consumption patterns — by time of day and season — before sizing a solar system. A poorly sized system optimised for peak harvest load will export expensively outside that window.

2. Confirm planning status. For roof-mounted systems, check Part 14 Class J conditions apply (no listed building designation, no conservation area restrictions on that elevation). For any ground-mounted element, engage the LPA early.

3. Get quotes from MCS-accredited installers. MCS accreditation is required for FETF grant eligibility and SEG registration. Obtain at least three quotes; ensure each covers G98/G99 grid connection notification, DNO approval, and metering.

4. Model the tax position. Confirm with your accountant that the full installation cost can be claimed under AIA in the intended accounting period, especially if you have already used AIA on other plant and machinery in the same year.

For a deep-dive on Class J and prior approval, see our dedicated guide to planning permission for agricultural solar.