Why polytunnels & glasshouses are an excellent fit for commercial rooftop PV
Heated UK glasshouses and large polytunnel complexes — particularly those producing salads, soft fruit, ornamentals, propagation, vertical-farm crops or year-round protected horticulture — have some of the largest commercial electrical demand profiles in UK agriculture. Supplementary lighting (LED grow-light systems running 14–18 hours per day in winter), heating (typically gas or biomass with electric heat-pump augmentation increasing), HVAC, irrigation pumps, and packing-line equipment combine to push annual electricity consumption for a mid-sized commercial glasshouse to 1–3 GWh, with the largest sites consuming 10+ GWh annually. The roof area available is correspondingly large — glasshouse complexes commonly cover 1–5 hectares with semi-transparent glazing, while polytunnel complexes can extend across 5–20 hectares. Agrivoltaic deployment over polytunnels (using semi-transparent panels above shade-tolerant crops) is emerging quickly in the UK.
System sizing for polytunnels & glasshouses
Glasshouse and polytunnel PV sizing depends heavily on the structure type. Conventional Venlo glasshouses with steel-frame construction can support rooftop PV on the structural ridge framework (typically 80–200 kW per hectare of glasshouse footprint), with the remainder of the glazing kept clear for natural light. Polytunnel installs are more complex — most polytunnels are designed for the polythene cladding to be replaced every 4 years, which complicates fixed rooftop PV. The emerging solution is elevated agrivoltaic installs (raised structural frames above the polytunnel with semi-transparent panels) or ground-mount installs on adjacent paddocks dedicated to PV. Vertical farm (CEA) sites with sealed enclosed buildings typically install PV on the building envelope or on adjacent ground-mount fields.
Typical polytunnels & glasshouses install at a glance
- System size range
- 100 kW–2 MW
- Panel count
- 185–3,700
- Roof area needed
- 600–12,000 sqm
- Annual generation
- 92,000–1.85m kWh
- Annual CO2 avoided
- 21–425 tonnes
Cost and economics
Glasshouse and polytunnel install economics in 2026: 100 kW–2 MW typical systems, 92,000–1.85m kWh annual generation. The scale of typical projects (often above 500 kW, sometimes above 2 MW) means PPA financing is widely used in this segment — third-party developers fund, install, own and operate the PV system on the glasshouse complex in exchange for a discounted-rate Power Purchase Agreement over 15–25 years. The feasibility study should model PPA, asset finance and capital purchase routes side-by-side in every glasshouse proposal.
Compare these numbers against the wider cost of farm-building solar in 2026 and the grants and finance routes available. Ask each installer to show its yield and financial assumptions in writing, and compare them with the farm solar payback calculator.
Compliance and regulation
Agrivoltaic translucent-panel installs over polytunnels need agronomic trial alongside structural assessment — different crops have different shade tolerance, and the PV-shading effect on yield must be modelled before full deployment. Polytunnel structural reinforcement is often required for any rooftop PV — typically a complete frame upgrade or, more commonly, perimeter ground-mount as a cleaner alternative. Glasshouse installs avoid these complications because the structural frame already supports significant dead load. Defra and NFU horticulture engagement on agrivoltaics is increasing — SFI has no agrivoltaic-specific action, so do not count SFI income in an agrivoltaic case. Planning policy for ground-mount alongside polytunnel complexes follows the standard 9m × 9m × 4m Permitted Development cap with full planning above.
Install programme and timeline
What an install involves: a structural and electrical survey, a design and written proposal, the DNO G99 application, procurement, installation and commissioning. Ask each installer for its programme in writing; the grid connection is usually the longest step, so apply early. See the planning guide for the Class J limits.
A modelled polytunnels & glasshouses scenario
A typical modelled UK glasshouse scenario: a Kent-based salad-grower running 4 hectares of heated Venlo glasshouses supplying a major UK supermarket with year-round leaves and herbs. Annual pre-install electricity spend £820,000 across HVAC, supplementary lighting, packing-line, and biomass-boiler auxiliaries. The modelled scope: 1.2 MW PV across the southern ridge of the glasshouse complex (using structural-frame mounting that doesn't shade the growing area) and a 600 kW ground-mount on adjacent unused paddock. A 500 kWh battery system supports the lighting demand peak that runs in winter mornings. Modelled year-one generation: 1.7 GWh. Modelled annual saving: £410,000 across cost avoidance and SEG export. Simple payback 4.9 years. At this scale the install becomes central evidence in a supplier's CDP Supply Chain return.
More modelled worked examples are in the case studies library; each is labelled as modelled, not a named client project.
Key features and capabilities for polytunnels & glasshouses
- Heated glasshouses and protected horticulture have massive supplementary lighting and heating loads
- Vertical farming and CEA sites exceptionally good PV fit
- Agrivoltaics over polytunnels emerging quickly (translucent panels, semi-shade-tolerant crops)
- Soft fruit, salads, ornamentals — supermarket-facing producers under Scope 3 pressure
Send your polytunnels & glasshouses roof details
Tell us the building, the roof sheeting and what you want to know. Send your details through the quote form and we reply by email. Before you sign with any installer, check their MCS certificate on the MCS register and ask for the structural, roof-condition and grid assumptions in writing.
Common questions
How much do solar panels for farm buildings cost in the UK?
DESNZ's solar PV cost data for 2025/26 puts the mean installed cost of 10-50 kW projects at about £1,267 per kW (median about £1,204 per kW), and non-domestic 10-50 kW installations at about £1,167 per kW. The series covers all building types, not farm buildings alone, and stops at 50 kW. Your price depends on roof access, any re-roofing, cabling distance to the intake and the grid connection. The cost page on this site sets out the regional figures and the method; treat them as a benchmark and compare written quotes against them.
Can we put solar panels on asbestos cement barn roofs?
Not directly: installers will not normally fix through asbestos cement sheets, so the roof is overclad or replaced before the panels go on. HSE says most work on asbestos cement is non-licensed provided the people doing it are informed, instructed and trained, and its task sheet A14 asks whether the sheets can be overlaid with non-asbestos material instead of removed. Price the roof work and the PV separately: the roof is building fabric, the PV is plant, and the two are treated differently for tax.
Which farm building should we install solar on first?
Prioritise by three criteria: (1) roof area and orientation — the biggest south-facing clear-span roof in sound structural condition wins; (2) on-site daytime load — dairy parlours, grain stores during harvest, intensive livestock houses, and farm workshops all have year-round or seasonal daytime baseload; (3) install access and biosecurity complexity — workshops and grain stores typically have lower biosecurity friction than poultry or pig units, but the latter often have much larger roofs. We rank each building during feasibility on payback, self-consumption, and complexity.
Will solar panels work on a curved or arched barn roof?
Generally no — modern PV requires a structural surface with adequate purlin spacing and slope (typically 5° to 35°). Curved Dutch-barn or hooped sheds need either a separate flat or pitched roof to be installed (rare), a ground-mount alternative, or — most commonly — a different building on the farm chosen as the PV host. We assess every farm holistically rather than fixating on a single building.
What grants are available for farm-building solar in 2026?
No capital grant for rooftop solar on farm buildings was open in England, Wales, Scotland or Northern Ireland when checked on 3 November 2026. What does apply: the 100% Annual Investment Allowance on the PV plant (UK-wide; solar is special-rate plant), Smart Export Guarantee income in Great Britain (Northern Ireland has no SEG; suppliers there set their own export rates), and the Workplace Charging Scheme if EV chargers are part of the project. The Sustainable Farming Incentive pays for land-management actions, not solar. The grants and funding guide sets out each nation and the alternatives when no grant fits.
Do we need planning permission for solar on agricultural buildings?
Rooftop solar on a non-domestic building such as a farm shed is usually permitted development under Class J of Part 14 of Schedule 2 to the GPDO 2015, inside its physical limits. Above 50 kW you must apply for prior approval on design, appearance and glare. Listed buildings and some designated land are treated differently, and ground-mounted arrays follow other rules. The planning guide on this site sets out the current rules; confirm with your local planning authority before you commit.