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. Where the load is high and constant, much like a dairy's milk cooling but at greater scale, a large PV system is consumed on site rather than exported, and self-consumption drives a strong return, with paybacks often around 5.5 years for well-matched sites. 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.

Horticulture also tends to supply retailers directly, so the Scope 2 reduction that solar delivers feeds straight into buyer sustainability requirements, the same retail pressure that flows through the milk contract. For a grower competing on price and environmental credentials at once, on-site generation is a genuine commercial asset rather than just a cost saving, and the auditable evidence of self-generated electricity increasingly forms part of how retail buyers assess their supply base.

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. When we design for a horticultural enterprise we 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. The result on a well-matched glasshouse or packhouse is one of the strongest returns in the whole farming sector.

What a typical horticulture install looks like and how we size it

Horticulture systems span a very wide range, from around 100 kW to 5 MW, roughly 185 to 9,200 plus panels, generating from about 92,000 kWh to 4.6 million kWh plus a year and saving from 21 to over 1,000 tonnes of CO2. 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 we model the PV 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

Projects range from around £90,000 to £4 million plus, reflecting the breadth of the sector, with paybacks near 5.5 years for sites with strong daytime self-consumption. 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 four to fifteen pence 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. Our cost guide works through the economics at glasshouse scale, including how the numbers shift when PV is combined with existing heat plant. The strongest paybacks in this part of the sector come where a high, steady refrigeration or lighting load sits beneath a large, simple roof, because almost every unit generated displaces an expensive imported one; the weakest come where a mostly daytime, seasonal load is paired with an oversized array that has to export much of its output, which is why we always anchor the sizing to the measured demand rather than the available roof.

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 four to fifteen pence per kilowatt hour for any export, keeping the meter working during low-demand spells. The Sustainable Farming Incentive is less directly relevant to a glasshouse than to grazing or arable land, but a mixed dairy and horticulture holding can still stack biodiversity and soil-health actions on the wider farm, worth roughly five hundred to five thousand pounds per hectare per year. The Farming Investment Fund may apply where solar is paired with eligible capital such as packing or cold-storage equipment. Welsh and Scottish growers should check the devolved schemes with their higher intervention rates of ten to forty per cent.

Compliance and sector considerations

Translucent panels above crops are an emerging option in UK horticulture, and we recommend an agronomic trial 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. Standard rooftop PV on packhouses and stores follows the usual agricultural permitted development rules within the Class A Part 14 size limits, while large ground-mount or glass-integrated schemes need full planning permission and, above 5 MW, an Environmental Impact Assessment. As with the dairy buildings, older structures may carry asbestos cement roofing under the Control of Asbestos Regulations 2012 that needs a licensed replacement first. A G99 grid application is required above 17 kW per phase, and the large loads typical of horticulture make an early DNO connection study essential before final sizing. We hold MCS commercial certification, NICEIC, RECC and TrustMark.

How we approach this kind of project

We begin with half-hourly meter data and, on a mixed holding, the dairy load as well, so the PV is sized to a true whole-site demand rather than a single building. We model the solar alongside any existing heat plant, combined heat and power or heat pumps, rather than treating it as a standalone item, because the interaction between those systems changes the optimal array size. We carry out structural and asbestos surveys before quoting, recommend an agronomic trial for any agrivoltaic element, and submit the G99 application early to start the DNO clock. You receive a fixed-price proposal with modelled generation and payback, and an insurance-backed workmanship warranty on the install.

Because horticultural schemes are often the largest single arrays on a dairy holding, the grid connection deserves particular attention. A glasshouse or packhouse array can run to several hundred kilowatts or beyond, well over the 17 kW per phase threshold for a G99 application, and on a capacity-constrained rural network that connection can take many months to confirm. We submit the application at the earliest possible point and, where export capacity is the bottleneck, we can size the system for self-consumption only so that the large on-site load does the work and the connection clears far faster. For a grower whose demand already absorbs most of the generation, that no-export design is frequently the right call, giving close to the full saving without waiting on scarce export capacity. We keep you informed of the DNO position throughout, because the connection, not the panels, is almost always what sets the timeline.

An illustrative example

As an illustrative composite based on typical UK projects, and not a real named client or real project: a glasshouse nursery run alongside a dairy enterprise, with high supplementary lighting and packhouse cold storage, installed around 400 kW across its packing and storage roofs, generating roughly 380,000 kWh a year and consuming most of it on site against a large baseload. Paired with existing heat plant, the PV covered a meaningful share of daytime demand, relief was claimed under the Annual Investment Allowance, and the payback came in around 5 to 6 years. The figures are illustrative and depend on your crop, glazing, lighting regime and tariff, which is why we model your actual demand before sizing anything. 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 request a free feasibility from your meter data, or read the dairy solar FAQs to see the questions other growers ask before they commit.