A commercial rooftop array is priced on three things that have nothing to do with the panels: how much of the generation the building will use itself during working hours, whether the roof can carry the extra load without strengthening, and what the network operator will let you export. Everything else on a commercial solar quote is arithmetic around those three answers, and a quote that does not state them is a price rather than a proposal.
Solar panels for businesses: self consumption decides the payback
Domestic solar and commercial solar are the same hardware with opposite economics. A house is empty when the sun is out, so most of the generation leaves the building and earns an export rate. A warehouse, a workshop, a school or an office is full when the sun is out, so most of the generation replaces electricity you would have bought at your business tariff. That difference is usually the whole case: the same array on the same pitch is worth substantially more on a building with a weekday daytime load than on one without, and the first thing a competent surveyor asks for is half hourly consumption data rather than a roof plan.
Business solar panels: the roof has to carry them, and somebody has to say so
Panels and their mounting add distributed load and change how wind acts on the roof, and on a large flat commercial roof the ballast used to hold a non penetrating system down can add more weight than the panels do. The structural question is not whether the roof looks strong; it is whether somebody with professional indemnity has confirmed in writing that it takes the imposed load with the array on it. Ask for that statement by name at quote stage. On an ageing single ply or asphalt roof there is a second question behind it, which is whether the covering has enough life left to sit under an array that is meant to last twenty five years.
Commercial solar PV: the grid connection can cap the system before the roof does
A commercial connection is applied for with the distribution network operator, and the answer can be yes, yes with an export limit, or yes but only after reinforcement you pay for. Export limitation is common and is not a disaster when the building uses most of its generation anyway, but it changes the sizing conversation: if you can only export a small amount, there is little point buying an array much larger than the daytime load. This is why a proposal that quotes a system size before the connection position is known is quoting a guess.
Commercial solar panels UK installers quote: what separates a proposal from a price
A usable commercial proposal names the modelled annual generation and the assumptions behind it, the self consumption fraction it assumes and where that came from, the export position with the network operator, the structural statement, the warranty terms for panels, inverters and workmanship separately, and the maintenance regime with its cost. A price names the kilowatt peak and the total. Compare two proposals and you are comparing engineering; compare two prices and you are comparing nothing.
Questions people ask about commercial solar panels
How big should a commercial solar energy array be?
Size it against the building's daytime load rather than the roof area. The usual approach is to model generation against half hourly consumption and find the point where extra panels start producing electricity the building cannot use, then check whether the network operator will let you export that surplus. On many commercial roofs the limiting factor is consumption or the export cap, not space.
Do commercial solar panels need planning permission?
Many commercial rooftop installations fall within permitted development, but the limits are specific about projection, siting and listed or protected buildings, and they differ from the householder rules. Check the position for your building before design work, because a scheme that has to move to satisfy planning usually gets smaller and more expensive.
Can the cost be written off against tax?
Capital allowances treatment depends on the business, the asset and the rules in force when the expenditure is incurred, so the honest answer is that your accountant should confirm it against current guidance rather than the installer. Get the tax position in writing from somebody who is liable for it, not from the salesperson.
What should I ask a commercial installer for?
MCS certification or equivalent competence for the scale of the job, the structural statement, the network operator correspondence, references for buildings like yours, and the accounts of the company that will hold your workmanship warranty. A twenty five year warranty from a company with two years of filed accounts is a promise with nothing behind it.
Does commercial solar battery storage change the payback?
It can, and it does not automatically. Storage pays where the business uses power outside daylight or where the grid connection caps what may be exported, so the surplus would otherwise be wasted. Where a building consumes almost everything it generates during the working day, a battery adds cost without adding much saving. Size it against the metered load shape rather than against the array.