Commercial solar panels for business

How solar works on a commercial building

Your roof has been sitting there for years doing very little, while the electricity bill turned up every month and the renewal quote crept upwards. Solar is one of the few energy decisions where a business changes that pattern rather than just shopping around inside it. This guide covers how commercial solar works in practice, what shapes the cost, where the tax treatment sits, what installation actually involves, and what happens to the power you generate but don’t use.

Panels on the roof generate direct current, an inverter converts it to the alternating current your building runs on, and the electricity feeds into your distribution board. Your equipment draws from it first. Only what the panels can’t cover comes in from the grid.

That’s the whole mechanism, and the important part is the order. Every unit you generate and use on site is a unit you don’t buy, so it avoids not just the cost of the electricity but everything layered on top of it, from network charges through to the Climate Change Levy where that applies. Whatever the building doesn’t use flows out to the grid, and that surplus can earn you money, provided an export tariff has been set up. Not every business gets round to that part.

Why it stacks up better for business than for homes

A house generates most of its power in the middle of the day, when the family is at work and school. The mismatch is the whole problem with domestic solar, and it’s why batteries matter so much on a house.

A commercial building doesn’t have that problem. A warehouse running conveyors, an office running air conditioning, a workshop running compressors, a shop running chillers and lighting. They’re all drawing hardest in exactly the hours the panels are producing. That means a far higher share of what you generate gets used where it’s worth most, on site, instead of being exported at a lower value.

Roof area helps too. Commercial roofs tend to be large, flat or shallow-pitched and unshaded, which is close to ideal. The constraint is usually electrical rather than physical.

What shapes the cost

Two systems of identical size on two different buildings can price quite differently, and the panels are rarely the reason. What moves the number is the roof structure and covering, how easy it is to get access and scaffolding up, the distance from the array to your electrical intake, and what your district network operator says about connecting generation in your area.

Scale works in your favour. Design time, mobilisation and the grid application cost roughly the same whether the system is small or large, so those fixed elements spread more thinly across a bigger array. This is why the price per unit of capacity falls as systems get bigger, and why undersizing a roof to save money sometimes costs more per unit than doing it properly.

Our guide to commercial solar costs breaks down what belongs in an installed price and how to compare quotes without being caught by missing scope.

Where the tax treatment and funding sit

There’s no universal national grant for commercial solar, whatever the adverts suggest. The meaningful support sits in the tax system. Solar equipment is treated as plant and machinery, so capital allowances apply, and for most businesses the Annual Investment Allowance covers the whole installation in the year it’s bought. Solar sits in the special rate pool, which puts it outside the full expensing regime, though the Annual Investment Allowance generally does the same job for typical commercial installations.

VAT is charged on commercial systems and recovered in the normal way by VAT-registered businesses. In England, eligible plant and machinery used for onsite renewable generation and storage carries a business rates exemption running to 2035, so adding panels doesn’t push up your rateable value. The devolved nations handle rating separately, so it’s worth checking locally.

Genuine funds do exist for particular sectors and regions, and government keeps a running list of funding to help businesses become greener. We’ve mapped the practical routes in our grants and funding guide. None of this is tax advice, and your accountant should confirm your own position before you commit to anything.

What installation involves

Survey and design first, then permission from your district network operator to connect generation, then the work itself, then commissioning. Most commercial rooftop systems fall under permitted development, so planning permission comes up less often than people expect.

The stage worth paying attention to is the handover. You should receive certification for the installation, written confirmation of the grid connection, warranties and access to the monitoring platform. Those documents are what a supplier asks for later when you register for export payments, and tracking them down years afterwards is considerably harder than filing them on the day. The full sequence is in our step by step installation guide.

What happens to the power you don’t use

Surplus generation goes to the grid whether or not anybody is paying you for it. The Smart Export Guarantee obliges larger electricity suppliers to offer at least one export tariff for eligible installations, and rates differ enormously between suppliers, which makes comparing them worth real money rather than being a box-ticking exercise.

Payments begin once the installation is registered and a tariff is in place. They aren’t backdated. We regularly come across businesses whose panels have been exporting unpaid for years because nobody finished the paperwork. If that might be you, the export tariff guide covers how to put it right, including what to do when the original certificates have gone missing.

Whether your building suits it

The physical checks are quick. Roof space with reasonable south, east or west exposure and no significant shading from neighbouring buildings or plant. A structure that can carry the additional load, which most steel-framed commercial buildings can. A roof covering in good enough condition that you aren’t installing over something due for replacement, because taking an array off and putting it back is an expense nobody enjoys.

Then the two that catch people out. Tenure, because a leased building needs the landlord involved early rather than late. And electrical headroom, since your authorised supply capacity and the local network’s spare capacity shape what the network operator will actually approve.

What to ask before you sign anything

Ask what the generation estimate is based on. A figure modelled from your own half-hourly consumption data means something. A figure from a national average doesn’t.

Ask what share of the generation the design expects you to use on site rather than export, because that assumption drives the entire financial case and it’s the one most often flattered.

Ask what’s included in the price and what sits outside it, particularly scaffolding, the network operator application, any electrical upgrades and commissioning. Ask who owns the relationship with the network operator. Ask what the workmanship warranty covers as distinct from the product warranties. And ask what happens about the export tariff, because a surprising number of installers treat that as somebody else’s job.

Frequently asked questions