Advice on small-scale solar for lower farm energy costs

Whether for heating, ventilation, drying or cooling, the payback on a solar investment can be as low as four years if the alternative is a high-cost conventional commercial electricity supply.

A six- to seven-year payback is pretty much guaranteed, say advisers, assuming that the installation is being funded with cash and the vast majority of the electricity generated is being used on site.

Domestic or commercial use across several properties, for example in a diversified business with let residential or industrial uses such as workshops, offices or retail units, is also popular, as well as electric vehicle charging.

See also: Know the energy efficiency rules for commercial lets on farms

The first step is to make a detailed study of the farm’s electricity demand and ensure you are only installing what you need, advises consultant Kieran Crowe, director and head of net zero buildings at the Low Carbon Alliance.

“If you’re making a significant investment, it’s worth getting a smart meter and monitoring your use for six or 12 months,” Mr Crowe suggests.

Get a qualified electrician to check the rating of existing cables – something that many solar installers also undertake.

“It’s also worth taking independent advice, particularly on evaluating the financial benefits, as quotes often include exaggerated predictions of energy savings,” he says.

1. Costs and payback

A 30kW rooftop array will cost between £30,000 and £40,000 installed, with the range accounted for by the quality of panels and inverters.

“An optimised system to your actual demands can have paybacks of six years or less, sometimes much shorter if you have a high electricity tariff,” says Mr Crowe.

“The commercial electricity market has softened a lot and is in the 35p-45p/kWh range now. At that level you could still see a payback in four years if you are using the electricity on site.”

2. Grid issues

30kW is considered microgeneration scale, but a grid application to the Distribution Network Operator (DNO) will be needed for the installation, costing between £500 and £600.

While grid access is an issue for larger projects, most 30kW installations on a three-phase supply will not encounter problems, says Mr Crowe.

If surplus power may need to be exported, the DNO may require a device to limit how much power can go to the grid when the local infrastructure needs upgrades to allow connection.

3. Roofs

Fragile and asbestos roofs are typical on farms, so these can present issues. Where this is the case, consider replacing roof finishes or installing an overclad PV system, suggests Mr Crowe.

Albeit more expensive, overclad PV systems create a waterproof roof over existing roof sheets. They incorporate guttering and the roof ridge, with blanks that allow light through the building.

4. Planning permission

Roof-mounted solar arrays of up to 1MW fall within permitted development rights (PDRs) in England. However, Scottish PDRs only allow up to 50kW of panels.

Small ground-mounted arrays have not been popular but are increasingly being considered.

Anything over 1kW that is ground mounted needs full planning permission, but for a 30kW project, this can be achieved for about £2,000, says Alex Monro of the Devon Energy Partnership.

“Ground mounted has the advantage of easier installation, particularly if there are fragile or asbestos roof considerations. Also, they are much easier and cheaper to clean and maintain.”

5. Selling to grid

Selling energy to the grid at small scale is likely to achieve only about 5p/kWh, which does not offer a payback on export alone, says Mr Crowe.

Higher prices of 10-12p/kW are available through what is known as a power purchase agreement, usually through an energy broker, but only for more than 25-30kW.

The numbers

• 41.4% UK electricity generated from renewable sources in 2022
• 9.6% from bioenergy Oct-Dec
• 18.6% from offshore wind Oct-Dec
• 12% from onshore wind Oct-Dec
• 2.1%from solar PV Oct-Dec
• 2.1% from hydro Oct-Dec