Why a dairy farm's electricity use sets the system size
Solar panels for dairy farms are sized against the electricity the farm uses in daylight, not against the roof. A dairy's demand comes from refrigeration of the bulk tank, water heating, vacuum pumps, lighting and, on robotic units, the robots themselves. The Dairy Group's study of UK dairy farms, reported by Farmers Weekly in 2014, found cooling, water heating and vacuum pumps each took roughly 25 to 30% of a dairy's electricity. The part of that demand that falls in daylight is the part solar meets directly, and it is worth more than exported power because it replaces electricity bought at your tariff rather than paid for at the export rate.
The number to start from is how much electricity the herd uses. AHDB and NFU Energy gave 400 to 600 kWh per cow per year as a typical range in 2021, with 250 to 300 kWh described as very low. The Dairy Group's older figures averaged 423 kWh per cow per year across a range of 231 to 811, and 0.06 kWh per litre of milk (range 0.03 to 0.09). Both are published benchmarks rather than measurements of your farm, so use your own bills and meter data where you have them.
How the herd-size figures are worked out
Start from annual use, which is cows multiplied by kWh per cow, then divide by the annual yield per kWp to find the array whose output over a year matches it. PVGIS estimates for a south-facing 35 degree roof with 14% system losses give about 886 kWh per kWp in Manchester, 965 in Liverpool, 968 in Birmingham, 981 in Leicester and 1,042 in Cardiff; the table below uses 950 as a round figure. That annual match is a ceiling, not a target. A conventional parlour milked at the edges of the day has its cooling and hot-water peaks outside the middle of the day, a robotic herd spreads its load across 24 hours, and whatever the farm cannot use is exported at the Smart Export Guarantee rate rather than saving the full price of imported electricity. The right size comes from half-hourly meter data and the milking times. Youngstock and dry-cow buildings add roof area without adding much load.
Herd size, annual electricity use and the annual-match array
Annual use is cows multiplied by 400 to 600 kWh per cow (AHDB and NFU Energy, 2021). The last column divides that by 950 kWh per kWp a year, a round figure inside the PVGIS range for England (886 in Manchester to 981 in Leicester). It is the array whose output over a whole year equals the herd's annual use, which is a ceiling rather than a target: a dairy cannot use all of a large array's midday output, so the array with the best return is usually smaller.
| Cows in milk | Annual use, kWh | Annual-match array, kWp |
|---|---|---|
| 100 | 40,000 to 60,000 | 42 to 63 |
| 200 | 80,000 to 120,000 | 84 to 126 |
| 300 | 120,000 to 180,000 | 126 to 189 |
| 500 | 200,000 to 300,000 | 211 to 316 |
| 1,000 | 400,000 to 600,000 | 421 to 632 |
The calculation is shown so you can check it: kWp = annual kWh ÷ 950. The dairy farm solar calculator lets you vary the share of output the farm uses, and how much electricity a dairy farm uses gives the sources behind the kWh-per-cow figures.
Costs and tax relief
We do not publish a price list. For scale, DESNZ's 2025/26 cost data gives a mean of about £1,257 per kW for 10 to 50 kW systems in Wales (a mean, and it includes domestic installs); larger rooftop systems usually cost less per kW, so ask for itemised quotes. Solar PV is plant and machinery: the £1 million Annual Investment Allowance usually means 100% relief in year one for a business under the limit, and the tax you save depends on your tax rate and profits. The Smart Export Guarantee pays for exported surplus; the best open fixed rates we found in early October 2026 were around 12 to 13p per kWh, with small suppliers at 3 to 6p, and avoided import is worth more than exported surplus. The dairy farm solar panel cost guide and the dairy farm solar calculator go further.
Funding routes in detail
The Annual Investment Allowance and the Smart Export Guarantee are the routes that apply to most dairy farms in England. The Farming Equipment and Technology Fund 2026 closed on 12 May 2026, Capital Grants 2026 has closed, and the Sustainable Farming Incentive pays for land management rather than panels; none of the pages we read in October 2026 listed solar PV. Wales and Scotland run their own schemes, which we have not confirmed. The dairy farm solar grants page lists each route with its status and the date we read it.
Compliance and sector considerations
What needs care is the install itself around a live working dairy. The installer has to work around slurry pit and silage clamp electrical safety, keep cabling clear of washdown and acid-wash areas, and schedule around calving rather than through it. In England, rooftop solar on a farm building is generally permitted development under Class J of Part 14 of the GPDO 2015, not the householder Class A: up to 50 kW is permitted subject to the Class J limits, and above 50 kW the council makes a prior-approval decision on design and appearance, including glare. A listed building falls outside Class J and needs planning permission and Listed Building Consent. 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. The most common blocker is the roof itself. Many pre-2000 farm buildings have asbestos cement sheeting, so an asbestos survey comes first, and the roof is often over-clad or replaced before panels go on. Under the Control of Asbestos Regulations 2012, careful removal of asbestos cement sheeting is generally non-licensed work (HSE), but it still needs a risk assessment, trained workers and controls. A G99 grid application is needed above 16 A (3.68 kW) per phase, and rural networks are often capacity-constrained, so the connection is usually the long pole of the whole project and is best started from day one. 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
For the electricity side, read how much electricity a dairy farm uses; for money, dairy farm solar grants, the dairy farm solar panel cost guide and the dairy farm solar calculator. If your dairy sits within a mixed holding, the pages on solar for arable farms and livestock farm solar may also apply. Then send an enquiry from your meter data, or read the dairy solar FAQs first.
Send an enquiry about dairy farms
We reply by email
- 1. Tell us about the farm: herd size, milking system, the postcode and roughly what you spend on electricity.
- 2. We reply by email with what we can tell you about your site, and the costs and funding that may apply.
- 3. No obligation. This site is a guide, not an installer, and it gives no fixed price.
Common questions
What's the payback for a dairy farm solar install?
It depends on how much of the output the farm uses. Simple payback is the installed cost divided by the yearly saving, so a farm that uses most of its generation on site pays back faster than one that exports much of it. Put your own figures into the dairy farm solar calculator; we do not quote a typical payback.