Solar panels for greenhouses — UK Specialist Installer

Why solar PV is a strong fit for greenhouses

Commercial greenhouses are among the most electricity-hungry property types in UK food production, and that load profile makes them an exceptionally strong fit for rooftop solar PV. Modern protected horticulture — tomatoes, cucumbers, peppers, herbs, ornamentals, soft fruit — relies on a stack of energy-intensive systems running through the daylight hours: supplementary HPS or LED grow lighting often used as photoperiod extension or DLI top-up; heating circulation pumps; thermal screen automation; ventilation fans; humidification; CO2 enrichment; irrigation pumps; and increasingly automated harvest and packing equipment. A typical 1-hectare commercial glasshouse consumes 600,000-1,200,000 kWh a year, with daytime baseload 2-3 times higher than night.

That daytime baseload pattern is the key economic driver. Solar generation peaks between 10:00 and 16:00 in summer and 11:00 and 14:00 in winter, exactly when greenhouse operations are at their busiest with ventilation, irrigation, packing, and supplementary lighting in shoulder seasons. Self-consumption ratios on properly sized greenhouse PV systems regularly exceed 80% without batteries — among the highest of any UK commercial sector. That high self-consumption directly translates into faster payback, with many greenhouse projects achieving 5-6 year simple payback compared to 7-8 years for office or retail.

The second driver is the sector’s economic pressure. UK protected horticulture has been squeezed since 2021 by combined gas price spikes, post-Brexit labour cost increases, and supermarket margin compression. Energy is now typically 30-40% of operating cost on a glasshouse — up from 15-20% pre-2021. That has driven rapid solar adoption among the larger UK growers, with several Fenland, Lea Valley, and Sussex operations installing 500 kW to 2 MW arrays in the past 24 months. Where those projects have batched onto the grid faster than DNO connection windows allow, growers have moved to private-wire and behind-the-meter strategies.

The third driver is the sustainability mandate from supermarket buyers. Tesco, Sainsbury’s, Marks and Spencer, Waitrose and Aldi all now require Scope 1 and Scope 2 carbon reporting from primary produce suppliers, with formal reduction trajectories tied to supply contract renewal. A Scope 2 reduction from on-site solar is the cleanest, most measurable, and most defensible carbon claim a grower can make. Several supermarket-aligned grower groups now mandate or strongly incentivise solar deployment as part of supplier development programmes.

The fourth factor is the agrivoltaic frontier. Semi-transparent BIPV (building-integrated PV) panels designed to replace glasshouse glazing are now commercially available from several European manufacturers, with the UK market beginning to develop credible installation capability. These solutions allow PV to sit directly within the greenhouse canopy rather than requiring separate roof structures, opening solar to operations where the existing glasshouse roof cannot take conventional load.

System sizing for greenhouses

The typical greenhouse PV system sits between 50 kW and 500 kW, comprising 92-925 panels and using 300-3,000 square metres of mounting area. The actual size depends on operation type, glazing structure, and load profile.

Polytunnel growers have the cleanest sizing path. Most large polytunnel operations have associated processing, packing, and chilling buildings with conventional metal roofs that take conventional rail-mounted PV without complication. A typical 5-hectare polytunnel soft-fruit operation might run a 50,000 sq m polytunnel block with a 2,000 sq m steel-roofed packing facility — that packing roof can host 200-300 kW of conventional PV directly.

Glasshouse growers face a more complex sizing decision. Modern Venlo glasshouse glazing is engineered to a specific loading capacity that excludes additional PV weight on the roof itself. The standard approach is therefore to install PV on adjacent buildings — boiler houses, packing sheds, water-storage tank covers — or on purpose-built solar canopies above hardstanding. Some operations use a hybrid layout where 60-70% of the PV is on adjacent buildings and 30-40% is mounted on a structurally reinforced section of the glasshouse roof.

Roof area scales with operation size. A 50 kW system needs roughly 300 sq m of mounting area. A 500 kW system needs 2,500-3,000 sq m. Many UK glasshouse and polytunnel sites have substantial roof area available across multiple buildings, making 200-500 kW systems realistic for mid-sized operations.

Constraints are dominated by structural loading. Lightweight aluminium-framed glass or polythene roofs typically cannot accept conventional ballasted or rail-mounted PV. Where direct glazing integration is desired, semi-transparent BIPV panels (typically 30-50% light transmittance) substitute for clear glass and provide both light to crops and electricity to the building, but at substantially higher £/kW than conventional PV — typically £1,800-£2,500/kW versus £750-1,000/kW for adjacent-building rooftop PV. Most growers therefore route conventional PV onto packing sheds, processing buildings, and boiler houses first, treating BIPV as a phase 2 option for direct glasshouse integration.

Cost and payback for greenhouses

A 50-500 kW greenhouse PV system in 2026 costs between £45,000 and £425,000 installed for conventional rooftop PV on packing sheds, boiler houses, or other rigid-roof ancillary structures. Cost per kilowatt sits at £900-£1,000/kW for systems below 100 kW, falling to £750-£900/kW for systems between 100 and 500 kW thanks to scale on inverters, mounting, and DNO fees.

Worked example. A 3-hectare glasshouse soft-fruit operation in East Anglia with annual electricity consumption of 480,000 kWh on a 25p/kWh industrial tariff spends £120,000 a year on electricity. A 300 kW system costing £255,000 installed (on the 1,400 sq m packing and processing roof, not the glasshouse itself) generates approximately 280,000 kWh in year one, of which about 235,000 kWh (84%) is self-consumed at 25p saving £58,750 in cost avoidance. The remaining 45,000 kWh is exported under SEG at an average 9p/kWh delivering £4,050 of income. Total annual benefit: £62,800. Simple payback: 4.1 years.

Tax relief sharpens the case. Under 100% Annual Investment Allowance, a profitable agricultural limited company at 25% corporation tax deducts the full £255,000 from taxable profits in year one, generating £63,750 of tax relief and reducing the net effective cost to £191,250. On that basis the post-tax simple payback drops to 3.0 years and the modelled 25-year IRR rises above 20%.

Funding routes are well developed in horticulture. Cash purchase suits the larger growers with accumulated retained earnings. Asset finance over 5-7 years is the dominant route, often using specialist agricultural lenders (Oxbury, AMC, NatWest Agri) who understand horticultural cash flow. PPA is increasingly common at the 500 kW+ end where institutional investors fund the system and growers contract to buy power at a fixed unit rate typically 30-40% below grid retail. SFI and Farming Investment Fund grant capture, where eligible, can underwrite 25-40% of capital. We model cash, asset finance, and PPA options in every greenhouse quote and show IRR side by side.

Compliance and regulation specific to greenhouses

Greenhouse solar deployment touches three regulatory layers. First, structural and design compliance. Glasshouse roof loading is critical and is rarely sufficient for conventional PV. Every project requires a structural engineer’s report on the specific glazing and frame system before any mounting design proceeds. Adjacent buildings (packing, processing, boiler houses) typically have steel portal-frame structures that take conventional PV without issue, but pre-1980 buildings or older Dutch-light timber-framed glasshouses need careful assessment.

Second, planning and permitted development. Most rooftop solar on existing agricultural buildings falls under permitted development rights for agricultural use under Class A Part 6 of the GPDO 2015. Larger ground-mounted installations or solar canopies above hardstanding may require full planning. Conservation area, AONB, or listed-status proximity (some Victorian glasshouses are listed) needs case-by-case assessment.

Third, the agrivoltaic regulatory frontier. Defra has not yet published formal UK guidance on agrivoltaic solar, but the SFI scheme has begun to recognise dual-use land where solar is co-located with active arable or horticultural production. The Sustainable Farming Incentive 2024 round included references to “diverse farming enterprises” that may capture agrivoltaic deployments, and several pilot schemes are running with Defra observation. Growers planning agrivoltaic glasshouse retrofit should assume the regulatory framework will continue to develop and design with future compliance flexibility in mind.

DNO connection matters. Greenhouse systems above 100 kW use G99 — DNO timescales typically run 6-18 months and can be longer in capacity-constrained rural networks (much of Lincolnshire, the Lea Valley, and parts of Sussex are now flagged as ANM-constrained). We submit DNO applications immediately after structural feasibility to compress the project timeline. Where the DNO timeline is too long, we can scope private-wire or behind-the-meter strategies that avoid full grid connection.

A typical greenhouse install scenario

A 4-hectare commercial cucumber grower in Lincolnshire operating a 38,000 sq m Venlo glasshouse with associated packing and processing facilities totalling 1,800 sq m of steel-roofed buildings. Annual electricity consumption: 620,000 kWh, on a 24p/kWh contracted industrial tariff. Existing bill: £148,800 a year. Glasshouse heating runs on gas (separate from PV scope).

The system specified: 350 kW rooftop PV array on the packing and processing buildings using 645 panels in a south-facing single-tilt configuration on the steel portal-frame roofs. Two 200 kW string inverters with integrated DC isolators. Glasshouse roof was structurally surveyed and ruled out for conventional PV. PVSyst yield: 322,000 kWh year one. Self-consumption modelled at 88% based on 12 months of half-hourly meter data showing strong daytime correlation with solar generation. Total installed cost: £298,000 inclusive of structural reinforcement to one packing building, DNO G99 application, and commissioning.

Year one results: actual generation 327,500 kWh, self-consumption 86% delivering £67,592 of cost avoidance, plus £4,131 SEG export income. Total benefit £71,723. AIA tax relief in year one for the limited company at 25% corporation tax: £74,500. Post-tax effective net cost: £223,500. Post-tax simple payback: 3.1 years. The grower financed 60% via 7-year asset finance from a specialist agricultural lender at 7.2% APR, with the remainder funded from retained earnings. Phase 2 BIPV semi-transparent retrofit on a 3,000 sq m glasshouse section is in design for 2027 deployment.

Trade-specific FAQs

Will solar panels shade my crops? Conventional opaque PV mounted on the glasshouse roof itself would significantly shade crops and is generally not specified. The standard approach is to mount conventional PV on adjacent packing, processing, and boiler-house roofs, leaving the glasshouse glazing untouched. Where direct glazing integration is desired, semi-transparent BIPV panels (typically 30-50% light transmittance) substitute for clear glass and have been shown to support crop yields within 5-10% of unshaded controls for many shade-tolerant crops in continental European and increasingly UK trials. Light-demanding crops (tomato, cucumber, pepper) need more careful design.

Can solar replace greenhouse glass? Yes — semi-transparent BIPV panels are commercially available from several European manufacturers (notably from Dutch and German specialist suppliers) and can substitute for clear glass in greenhouse glazing. Cost is currently £1,800-£2,500/kW versus £750-£1,000/kW for conventional rooftop PV on adjacent buildings, so the economic case favours conventional PV for the bulk of the system with BIPV as a targeted phase 2 option for specific glasshouse sections. The technology is maturing fast and we expect cost parity within 5-7 years.

Does agrivoltaics work in the UK? Increasingly yes. Several UK pilot schemes are now in their second or third growing season, with documented results showing crop yields within 5-15% of unshaded controls for shade-tolerant crops (leafy greens, soft fruit, herbs) under mounted solar. Defra is observing several pilots and the SFI scheme has begun recognising dual-use horticultural land. UK agrivoltaic deployment lags Continental Europe by 2-3 years but is accelerating. We design with this in mind on long-life infrastructure projects.

What grants are available for greenhouse solar? SFI (Sustainable Farming Incentive), Farming Investment Fund, and Farming Equipment and Technology Fund all have streams that may cover solar PV on horticultural holdings. The UK Agri-Tech Centre and Innovate UK fund agrivoltaic R&D. Most commercial deployments rely primarily on the 100% Annual Investment Allowance for tax-shielded capex, with SFI grants as a secondary funding layer. We map all available grants for your specific operation as part of the desk feasibility.

How long is the DNO connection wait for a 200-500 kW greenhouse system? G99 connections at this scale typically take 6-18 months from application to live, but can be longer in capacity-constrained rural networks. Lincolnshire, the Lea Valley, much of East Anglia, and parts of Sussex have ANM (active network management) constraints that can extend timelines or require curtailment agreements. We submit DNO applications immediately after structural feasibility and will scope private-wire or behind-the-meter alternatives if the timeline is impractical for your project deadline.

Next steps

The first step is a free desk feasibility study. Send us 12 months of half-hourly meter data plus an aerial image or roof drawing of your packing, processing, and glasshouse buildings, and within 7 working days we will model indicative system size across each available roof, generation forecast, self-consumption ratio, financial DCF, AIA tax relief, and IRR — using your actual consumption pattern. We will flag DNO capacity risk for your specific postcode and scope private-wire alternatives if relevant. To start visit our quote page, review typical costs and payback, explore grants and funding routes, or read our sister farms sector page. Free desk feasibility from your half-hourly meter data.