Solar and battery for business premises: what does the install involve?

How is a business install different from one on a house?

Mainly in when the power gets used, how it connects, and what the roof is made of.

A house generates at midday and uses its electricity in the evening, which is why a home battery earns its keep. A workshop, an office or a farm uses power in daylight, so far more of what the panels make is used as it is made. That is the commercial case, and it is why the battery is a separate decision.

Most business premises also have a three phase supply, a system large enough to need a G99 application, and profiled sheet on a steel frame rather than tiles on timber. Our domestic solar and battery article covers the house version.

Why does the installer want a year of half hourly data?

Because it is the only honest way to size the system.

Most business supplies are settled half hourly, so your supplier already holds what you used in every thirty minute slot for the past year. Ask for it. Modelled against that, the proposed array shows how much would be used on site, how much would export, and whether a battery would ever fill and empty in a way that pays. An installer who quotes from the roof area alone is guessing.

Here is the part a sales-led quote leaves out. On a flat unit rate with no peak charges, in a building that works daylight hours, the panels do nearly all the work and the battery often adds little beyond cost and a maintenance item. A battery pays when there is a real gap between day and night prices, a peak charge it can shave, or a night shift it can serve. We will show you that in your own data before recommending one.

What is a G99 application and why is it the slow part?

It is the network operator’s permission to connect generation, and it must be in place before the system is switched on.

Generation below 3.68 kilowatts per phase connects under G98 and can be notified afterwards. Anything above that, which is almost every commercial system, connects under G99 and needs an application first. G99 has a fast track for smaller schemes on type tested inverters, up to 32 or 60 amps per phase depending on the route, usually with a G100 scheme that caps export.

Above those thresholds the network operator studies the local network first, and the answer can be a lower export limit than the roof could deliver, a condition, or a reinforcement charge. That is why the application goes in before the kit is ordered. The install takes days. The approval takes weeks, longer on a constrained rural network. We handle it as part of the job.

What gets checked on the roof before anything is bolted to it?

Its structure, its covering and who actually owns it.

A steel portal frame was designed for snow and its own cladding, not for rails and panels, so a structural engineer confirms the frame and purlins will take the weight before the design is fixed. Flat roofs get the same check plus a look at the membrane, because nobody wants to lift a working array to re-cover a roof in five years.

Then the covering. Many older units still carry asbestos cement roof sheets. They are fragile, cannot be walked on and cannot take fixings, so an array cannot go on them. The building owner has a legal duty to know where asbestos is, and the register should say what the roof is made of. If it is asbestos cement, this is a re-roofing conversation first, and we would rather say so on the first visit than after a quote.

Finally, ownership. If you lease the premises the roof is usually the landlord’s, and the lease says whether you may fix anything to it and who owns the system when you leave. Get that in writing first. We do the electrical installation and certification and bring in a roofing specialist for the mounting.

What does the electrician actually do on site?

The whole AC side: the connection, the protection, the metering and the paperwork that proves it is safe.

The inverters need their own way into your distribution board, sized and protected for a supply that now flows both ways, with the generation balanced across the three phases. There is isolation on the AC and DC sides, labelling so the next electrician and the fire service know the building generates, generation and export metering, and the export limitation scheme where the network operator has asked for one.

The battery wants a firm floor, ventilation, clearance and a location your insurer is happy with, usually a plant room, a compound or an external cabinet. Tell your insurer before it goes in.

The work is tested and certified to BS 7671, commissioned to the G99 conditions and confirmed back to the network operator. As an employer you have a standing duty under the Electricity at Work Regulations to keep your electrical systems safe, so the handover pack matters. Our commercial solar and battery page describes how we run the electrical side, with isolations phased around trading where the premises stay open.

Do we need planning permission, and what paperwork should arrive at the end?

Usually not, and a specific set of documents.

In England, solar on the roof of a non-domestic building is permitted development under Class J of the General Permitted Development Order, provided the panels sit no more than 0.2 metres proud of a pitched roof or one metre above a flat roof, stay a metre from the roof edge, and the building is not listed or a scheduled monument. Above the microgeneration threshold, which for electricity is 50 kilowatts, you must first ask the council whether prior approval is needed for design and appearance, particularly glare on neighbours. It is lighter than a planning application, but it goes on the programme alongside the G99 application.

At the end you should hold the electrical installation certificate, the G99 commissioning confirmation and the network operator’s acceptance, the structural sign off, the commissioning records, an operation and maintenance pack, and the certification your export tariff needs. The Smart Export Guarantee covers solar up to five megawatts, and the suppliers who pay it ask for evidence the install meets the scheme’s standards, which for smaller systems means MCS certification or its equivalent. Check who is certifying the system before you sign.

What changes the price of a commercial solar and battery install?

We price from your data and your building, not a rate card. These are the things that move it.

• The array size your consumption justifies, which is often smaller than the roof.
• Whether a battery earns its place, and how large, which your tariff decides.
• The roof: structure, covering, height and access.
• The connection: the G99 route, any export limit, any reinforcement the network operator asks for.
• The run from roof to distribution board, and whether the board can take the new supply.
• Whether the premises stay open during the work.

Send us a recent bill and twelve months of half hourly data through our quote page and we will tell you whether the numbers work before anybody climbs on the roof.

Questions we get asked about this