Glasshouse / Horticulture: Solar panels for dairy farms

Why a glasshouse or nursery near a dairy is an exceptional solar site

Some dairy businesses diversify into protected horticulture, a glasshouse, a polytunnel nursery, or a packhouse for vegetables and salads, and where they do, that enterprise is one of the most energy-intensive forms of farming in the country. Glasshouse heating, supplementary lighting, irrigation pumps, packing lines and cold storage add up to a large, steady electricity demand that runs for much of the year, and that demand is exactly what makes solar pay. Vertical farming sites are even more pronounced, with lighting loads that dwarf almost every other farm type. For a dairy that runs a horticultural side, solar can cover both the parlour and the packhouse from the same investment programme, spreading the fixed costs of survey, design and connection across a bigger, more valuable system.

What makes horticulture different from the rest of a dairy holding is the sheer size of the electrical load relative to the buildings, and the fact that much of it is controllable. Supplementary lighting, in particular, is run to a schedule that a grower can shift, which opens up the option of timing some of that load to coincide with peak generation. Cold storage and refrigeration, on the other hand, run continuously and behave very much like a dairy's milk cooling, soaking up generation around the clock and pushing self-consumption high. A horticultural design should map those load types separately, because a lighting load that can be shifted is a different sizing problem to a refrigeration load that cannot, and the right array is built around both.

What a typical horticulture install looks like and how it is sized

Panels usually sit on packhouse and storage roofs rather than the glass itself, which keeps the array simple and the access straightforward, though agrivoltaic glazing above crops is an emerging option. Because heating and lighting loads can be enormous, solar is frequently part of a wider energy strategy that also includes combined heat and power or heat pumps, and on a mixed dairy and horticulture holding the PV is best modelled as one element of that whole-site picture, alongside the milking load, rather than in isolation. The packhouse and cold-store roofs are often the best starting point, since their refrigeration runs through the day and into the night in a way that mirrors a dairy's cooling demand and supports very high self-consumption.

Costs, payback and tax relief

The 100% Annual Investment Allowance writes off qualifying plant against profit subject to the annual one million pound cap, and larger schemes that exceed a single year's allowance can be structured so relief is taken across more than one tax year. The Smart Export Guarantee covers surplus export at a few pence to about 12-13p per kilowatt hour, although a high-load glasshouse exports little because its own demand absorbs the generation. Cost per kilowatt falls as the system grows, so a large glasshouse array is often more cost-effective per panel than a small parlour install. The cost guide works through the economics at glasshouse scale, including how the numbers shift when PV is combined with existing heat plant.

Funding routes in detail

The 100% Annual Investment Allowance covers qualifying plant up to one million pounds per year, and larger glasshouse schemes that exceed the annual cap can be planned so relief is taken across more than one tax year rather than lost. The Smart Export Guarantee pays a few pence to about 12-13p per kilowatt hour for any export, keeping the meter working during low-demand spells. Farm grant schemes open and close, and none of the English schemes we read in October 2026 listed solar PV; the dairy farm solar grants page lists each route with its status and the date we read it.

Compliance and sector considerations

Translucent panels above crops are an emerging option in UK horticulture, and an agronomic trial is advisable before any full agrivoltaic deployment so you can see the effect on yield for your specific crop before committing the whole site. Shade-tolerant crops such as leafy greens, soft fruit and hops are the usual candidates for trials, and the right answer is crop-specific rather than general, so a small trial area protects you from committing capital before the agronomy is proven. In England, rooftop solar on packhouses and stores is generally permitted development under Class J of Part 14 of the GPDO 2015, not the householder Class A, subject to the Class J limits; large ground-mount or glass-integrated schemes are treated differently, need the planning position checking with the local authority, and can require an Environmental Impact Assessment. In Wales, solar PV on a non-domestic building falls under Part 43, Class A of the Welsh general permitted development order, and in Scotland under Class 6J of the Scottish order; each has its own limits and exclusions, so check the rules for your building before relying on permitted development. As with the dairy buildings, older structures may carry asbestos cement roofing, and an asbestos survey comes first, and the roof is often over-clad or replaced before panels go on. A G99 grid application is required above 16 A (3.68 kW) per phase, and the large loads typical of horticulture make an early DNO connection study essential before final sizing. When comparing installers, ask for their MCS certificate number and check it on the MCS database, and check NICEIC, RECC and TrustMark membership with the issuing bodies. SEO Dons Ltd publishes this site and does not install.

Where to go next

A larger glasshouse with extensive supplementary lighting could justify a far bigger array, well into the megawatt range, where the cost per kilowatt falls and a portion of the controllable lighting load can be timed to coincide with peak generation; a smaller nursery with mostly daytime packing and refrigeration would point to a more modest system that the baseload absorbs almost in full. In both cases the design follows the load, and the relief under the Annual Investment Allowance applies to the qualifying plant in the year it is installed, subject to the annual cap, with larger schemes planned across more than one tax year where needed.

If milking is the core of the business, start with solar for dairy farms, and for dual land use on the wider holding see agrivoltaics in the UK. Compare the figures on the cost guide and the grants and funding page, then send an enquiry from your meter data, or read the dairy solar FAQs to see the questions other growers ask before they commit.