Solar panels for factories and manufacturing sites

Why manufacturing loads suit solar

The value of solar depends heavily on self-consumption: the share of generation you use yourself rather than export. Manufacturers are usually in a strong position because their demand is large, three-phase and concentrated in working hours. Typical loads include:

• Motors driving pumps, fans, conveyors and mixers
• Compressed air, which is often one of the largest single electrical loads in a factory
• Machining centres, presses, injection moulding and extrusion lines
• Electric ovens, kilns, curing and drying processes
• Welding, plating and other process equipment
• Space heating, cooling and lighting across large production halls

On a site running one or two shifts, Monday to Friday, a rooftop array will often cover only a portion of daytime demand, so very little is exported. That is the opposite problem to a lightly used shed, and it usually means the roof, not the demand, sets the limit on array size.

Weekends and shutdowns are where the picture changes. If the plant stops on Saturday and Sunday, or closes for two weeks in August, generation in those periods will largely be exported unless there is a baseload such as refrigeration, compressors left running or extraction. The survey looks at your half-hourly data to see what the site actually draws when production is off, because that figure has a real effect on the payback.

Peak demand and capacity charges

Solar reduces the units you buy. It does not reliably reduce your peak demand or your agreed supply capacity, because your highest demand may fall on a dull winter morning when the panels produce little. If capacity charges or maximum demand penalties are a significant part of your bill, battery storage is the tool that addresses them, and a survey can model solar and storage together.

The site and building issues a factory survey checks

Roofs of different ages

Factories are often a patchwork: an original building with later extensions, each with a different roof. You might find a north-light sawtooth roof on the oldest section, fibre cement sheets on a 1970s extension and a modern composite panel roof on the newest bay. Each needs its own assessment for condition, remaining life, fixings and load capacity. Older fibre cement roofs may contain asbestos, which has to be identified before anyone works on them; the asbestos roofs page explains the options.

Roof-mounted plant and process emissions

Extraction fans, ducting, flues, air handling units and dust collectors are common on factory roofs. They take up space and cast shade, and they need maintenance access kept clear. Process emissions can also matter: oil mist, dust or other deposits settling on panels reduce output and may mean more frequent cleaning. If any area of the site is classified for flammable atmospheres, electrical equipment must be kept out of those zones or specified accordingly.

The electrical system

Manufacturing sites usually have a three-phase supply and many have a high voltage connection with their own transformer. The survey looks at:

Installing without stopping production

Most of the installation happens on the roof and can run alongside normal work. The final electrical connection usually needs a short shutdown of the relevant board, which is best planned into an existing maintenance window. Telling the surveyor about planned shutdowns early saves months of waiting later.

Finance and ownership questions for manufacturers

Because self-consumption is usually high, factories tend to see savings close to their own unit rate on most of what they generate. Our commercial solar cost guide gives illustrative installed prices per kWp, which fall as systems get larger.

• Buying outright: a manufacturer that is profitable can often claim significant tax relief in the first year. Solar panels are special rate assets; the Annual Investment Allowance can give 100% relief up to its limit, and companies may also claim the 50% first-year allowance. See capital allowances and check the treatment with your accountant.
• Power purchase agreement: suits sites that want to keep capital for production equipment. The funder owns the system and you pay for the electricity at an agreed rate, usually over a long term.
• Asset finance or leasing: spreads the cost over a fixed term while the business keeps the savings, which suits manufacturers that prefer predictable monthly payments.

Two further questions are specific to manufacturing. First, how settled is the site? A business planning to relocate or significantly change its process in the next few years should weigh that against a long payback horizon. Second, are your customers asking about emissions? Many manufacturers now report energy and emissions data to larger customers, and on-site generation can form part of that. Our solar and carbon reporting guide explains how it is usually treated.

What to have ready for a factory survey

• 12 months or more of half-hourly data for every supply on site
• Shift patterns, typical weekend loads and dates of annual shutdowns
• Single line diagram, switchboard schedules and transformer details if you have an HV supply
• Details of any CHP, standby generation or existing solar
• Roof drawings for each building and any history of repairs or leaks
• Asbestos register for older buildings
• Any hazardous area classification drawings
• Plans for new production lines, electrification of gas processes or expansion

The more of this the surveyor has before the visit, the more precise the design and savings model will be. Request a free survey to get started.