Renewable Energy for Cornwall Farms and Agricultural Buildings

The standard Cornish farm has at least one large south-facing steel-portal building suitable for 50-300 kWp of roof-mounted solar PV. A typical 12m x 30m grain store roof carries 80-110 kWp; a paired pair of dairy buildings often hits 200 kWp; large finishing sheds can take 300-400 kWp. At Cornwall's 1,298 kWh/m²/yr irradiance a 100 kWp array generates 95,000-115,000 kWh annually.

Structural assessment is non-negotiable. Many Cornish ag buildings were erected to 1980s loading codes that don't account for an additional 12-15 kg/m² of PV plus rails. We commission a structural engineer survey on every install above 30 kWp — typical cost £600-£1,200 — and where reinforcement is needed (additional purlins or rafters) the cost runs £5-15k for a 100 kWp barn. Below 50 kWp many roofs pass without modification.

• Permitted development applies to most ag buildings under Class A of Part 14 GPDO up to 1MW where building height stays under 9m and panels don't overhang the roofline. Above 1MW you need full planning
• Asbestos roofs (still common on pre-1999 sheds) can be over-clad with metal sheet during the install — we partner with a HSE-licensed contractor for the over-clad and integrate the structural and electrical works in one programme
• Self-consumption vs export — dairies with high daytime base load self-consume 60-80%, arable farms often only 15-25% so export tariff matters more
• SEG tariffs April 2026 — Octopus Outgoing Fixed 15p/kWh; E.ON Next 12.5p; Good Energy 14p; Bulb Smart Export 13p — all 12-month minimum terms

The old Feed-in Tariff is closed (last installations registered March 2019 are still receiving payments) but the export-only economics under SEG plus self-consumption avoidance against 28-34p commercial import tariffs typically deliver 6-8 year paybacks for farms with reasonable daytime load.

A 200-cow dairy parlour uses 180-240 kWh per day in hot water alone (parlour wash-down at 65°C, plant clean-in-place at 85°C, plus general yard washing). Combined with vacuum pumps, milk pump, ice bank refrigeration and bulk tank cooling, total daily electrical draw sits at 350-550 kWh. This is one of the highest-IRR air-source heat pump deployments in Cornish agriculture.

The 2026 standard spec: a high-temperature ASHP (Mitsubishi Ecodan QUHZ R744 CO2, Daikin Altherma 3 H HT, or Vaillant aroTHERM plus VWL HT) sized at 16-30kW, feeding a 1,500-3,000L well-stratified thermal store charged overnight on cheap-rate electricity and topped up by PV during milking gaps. Plant CIP at 85°C requires either CO2 R744 refrigerant capability or a small electric boost element on the highest-temperature outlet. Parlour wash and yard washing run from the bulk store at 50-65°C.

Pair this with milk pre-cooling using plate heat exchangers that recover heat from the bulk tank refrigeration condenser, pre-warming wash water from 12°C to 35-40°C before the heat pump lifts it the rest of the way. This single retrofit (typically £8-14k) often delivers 35-45% additional energy reduction and pays back in under three years. We've delivered 23 milk pre-cooling integrations across Cornwall since 2023.

Cornwall's main arable areas around Bodmin, Saltash, Launceston and the Roseland Peninsula run grain dryers from late July to October — typically continuous-flow Westfield, Master or Allmet machines drawing 80-160kW peak with daily throughputs of 30-80 tonnes. Replacing oil or LPG burners with electric heat pumps for grain drying is technically possible up to about 60°C drying temperature but requires careful thermal store design and is rarely the right answer for the highest-temperature drying.

What does work: pairing a large rooftop solar array on the grain store itself with a battery and direct-drive ducted electric heating for the lower-temperature finishing pass, retaining the oil or LPG burner only for the initial high-temp moisture knockdown. This reduces fuel use by 40-60% without compromising drying schedule. For continuous-flow operators we increasingly recommend a 500 kWp+ array with 200 kWh battery, sized to displace the diesel generator that backs many remote dryers during grid constraint events.

Biomass (wood chip via the legacy Renewable Heat Incentive — closed to new applicants since March 2021 for non-domestic) is no longer the financial slam-dunk it once was. New biomass is typically only sensible where you have on-farm timber resource and a grain dryer needing 70°C+ that genuinely can't run on heat pump. We assess biomass vs ASHP vs hybrid at feasibility.

Class Q permitted development continues to drive farm diversification — converting redundant ag buildings to dwellings (now up to 10 dwellings or 1,000m² under the May 2024 amended GPDO). Energy strategy is critical because: (1) PD prior approval requires demonstration that the building can be made habitable without major structural work; (2) new dwelling EPC requirements demand at least a B rating in practice for prior approval to succeed; (3) buyers and renters expect heat pump heating not oil; (4) BUS does apply to Class Q-converted dwellings as they become genuine domestic properties.

Our 2026 Class Q energy package per dwelling: 5-9kW air-source heat pump (BUS-eligible at £7,500), 5-7 kWp roof or in-roof PV, optional 5-10 kWh battery, 7kW EV charger. Total spend £18-28k per dwelling, of which £7,500 BUS plus 0% domestic VAT means net cost to landlord around £14-20k. Adds £35-65k to dwelling sale value and supports an EPC A rating in most layouts.

Farm shops, café operations and on-farm holiday lets get the same hospitality treatment as our hotels and restaurants page — PV, ASHP, EV, often a 30-100 kWh battery for changeover-day load smoothing. Many Cornish farm shops also benefit from cold storage heat recovery for café hot water.

The 2026 funding stack for Cornish farms:

• SFI 2024 expanded offer — energy efficiency actions (BNG-12, EFA-2) pay for habitat creation around solar canopy installations
• Farming Equipment and Technology Fund (FETF) Round 4 grants up to £25k for energy-efficient kit including specific items in the Animal Health and Welfare list
• Improving Farm Productivity Grant — 25-40% capex on solar PV up to 100 kWp where used for self-consumption, max grant £100k
• IETF Phase 3 — 30% capex above £100k for combined heat recovery and process heat decarbonisation (relevant to dairies)
• BUS — £7,500 per Class Q dwelling for ASHP
• SWIG Finance + Defra Future Farming Resilience Fund — Cornish CDFI loans blended with feasibility grants
• Annual Investment Allowance 100% first-year on plant up to £1m
• Full Expensing from April 2024 — 100% deduction on main rate plant in year 1 (uncapped)

We sequence applications carefully — many funds preclude double-counting, but FETF + SEG + AIA + Improving Farm Productivity are stackable on different elements of a single project. Our grants and funding service handles the full applications including SBI and CRN setup if you don't yet have one. Speak to us before approaching RPA — sequence matters.

Working farms can't shut down. We programme installs around milking schedules (avoiding 5-9am and 4-7pm), harvest windows (no roof works on grain stores July-October), lambing and calving peaks. Most dairy parlour ASHP retrofits run as planned 5-day shutdowns during dry-cow periods, with a temporary diesel water heater on standby. Solar installs on harvested grain stores between November and June are the standard window.

DNO connection — large rural Cornish farms often share a single 11kV transformer with two or three neighbours. A 250kWp PV install with G99 application can take 4-9 months and may return a connection offer requiring a transformer upgrade (£25-80k typical contribution). We pre-screen substation capacity at feasibility using NGED Connection Information Portal data, avoiding the late-stage shock.

Slurry pit and silage clamp clearances under the Farming Rules for Water Code constrain ground-mount solar siting and battery container locations — we factor these into every layout. Battery containers also need 3m fire spacing under BRE Digest 489 from any habitable structure or fuel storage. None of this is hard but it requires a designer who works on farms regularly. We do.