Offices: Solar panels for commercial property

Why an office building is one of the most natural homes for commercial property solar

An office is the textbook case for solar panels on commercial property, because the hours the building draws power are almost exactly the hours the roof generates it. IT racks and servers, air conditioning and ventilation, lighting and small power all run hardest between mid-morning and late afternoon, which is precisely when a south-facing array is at its strongest. That overlap matters more than anything else, because the electricity you use on site is worth four or five times more than the electricity you export, and an office that is busy from roughly 06:00 to 18:00 will use most of what it makes. For a building owner or occupier, that turns a flat-roofed or pitched office block into a quietly productive asset rather than a pure cost centre, and it is the single biggest reason offices tend to pay back faster than people expect.

There is a second reason offices keep coming to us, and it is about the building itself rather than the meter. Solar lifts an EPC rating, and for commercial property that is no longer a nice-to-have. Minimum Energy Efficiency Standards already bar the letting of anything below band E, the threshold is set to rise to band C by 2027 and band B by 2030 for non-domestic property, and an office that cannot be let is an office that has lost a chunk of its value. Panels are one of the most cost-effective ways to move an office up a band or two, so the same project that cuts the bill also protects the lettability and the capital value of the building. Add to that the ESG questions that now flow down from larger clients and investors, and an office array becomes an asset that defends your bill, your building value and your standing with the firms you sell to all at once.

What a typical install looks like and how we size it

For an office we usually design a system in the 30 to 150 kW range, which is roughly 55 to 275 panels across about 200 to 900 square metres of roof. A system that size generates in the region of 27,000 to 138,000 kWh a year and saves somewhere between 6 and 31 tonnes of CO2 annually. We never simply fill the roof. Sizing comes from your half-hourly meter data and the genuine shape of your day, because an IT, HVAC and lighting baseload that sits at 60 to 80% of total consumption is exactly the kind of steady daytime demand that solar serves well. The aim is to target annual generation at around 60 to 80% of current consumption, so that self-consumption stays high (typically 55 to 75% without a battery) rather than leaving you exporting cheaply at the wrong times.

A few practical things shape the final number on an office roof. Plant rooms, rooflights, parapet shading and the orientation of a pitched roof all reduce the usable area, so the panel count we quote is what genuinely fits and performs, not a headline figure based on the gross footprint. Where the roof is flat we use ballasted or low-penetration mounting on an east-west layout to spread generation across the day, which suits an office load better than a single south-facing block that peaks at noon. Battery storage is not usually needed below 100 kW, but for a larger office with meaningful evening or weekend baseload, perhaps a building with server rooms or 24-hour security and lighting, we model a battery so the surplus is stored and used rather than exported. Every system we design is built to be battery-retrofittable, so if you would rather wait until you have a year of real generation data before sizing storage, the door stays open.

Costs, payback and tax relief

An office project typically lands between £30,000 and £150,000 depending on roof area and load, with a simple payback near 7 years and the electricity effectively free for the fifteen to twenty plus years after that. Cost per kW is typically in the £900 to £1,300 band below 100 kW and falls towards £750 to £950 per kW on larger systems, so a bigger office roof generally buys cheaper generation. The biggest financial lever is tax: solar PV qualifies as plant and machinery, so the 100% Annual Investment Allowance lets a profitable company write off the full cost against profit in year one, worth an effective saving of around a quarter of the project value for a limited company against current corporation tax rates. On an £80,000 office install that means roughly £20,000 of tax relief and a net cost near £60,000.

The Smart Export Guarantee pays you for any surplus, which matters for offices that empty out at weekends and tend to export 25 to 45% of generation, at rates that have sat in the 4 to 15p per kWh range. Office-only sites with moderate weekend usage tend to land at the longer end of the payback range, while buildings with a heavier baseload reach the shorter end, and adding a battery can extend payback by a couple of years but lift annual savings meaningfully. Our cost guide sets out worked numbers for different building sizes, and we model the export economics from your real consumption rather than a generic assumption.

Funding routes in detail

Most office owners and occupiers we work with do not pay capex up front. The 100% Annual Investment Allowance is the foundation: solar counts as qualifying plant and machinery up to the annual cap, and almost every office install sits well below it, so the whole cost is expensed in year one. For an unincorporated business on the cash basis, similar reliefs apply, and our finance team works with your accountant to confirm the right route rather than guessing. On top of that, asset finance over five to seven years is usually cash-flow positive from month one, because the finance payment is smaller than the bill it replaces, and you own the asset outright at the end of the term.

Regional support can also apply. Several combined authorities, including the Greater Manchester, West Midlands, West Yorkshire and Liverpool City Region authorities, have run SME decarbonisation grant rounds worth roughly £5,000 to £50,000 under names that change from round to round, and the British Business Bank Recovery Loan and Growth Guarantee scheme can fund capital investment in renewables from £25,000 upwards with a government-backed guarantee where a main bank is reluctant. Where you would rather carry no capital risk at all, a power purchase agreement is an option: a funder owns the array and you buy the power it generates at a fixed rate below grid price, saving from day one with no outlay. We help you check which of these are live in your region at the time you build, because the grant landscape moves.

Compliance and sector considerations

Most offices fall under Permitted Development as Class A Part 14 of the GPDO, so a rooftop array on a standard office block usually needs no planning application, though a high street or conservation-area frontage can be the exception and a listed building always needs Listed Building Consent. Your insurer may ask for the array to be integrated with the fire alarm, which we design in from the start, and any building from before 2000 needs an Asbestos Management Survey before work begins. Most insurers continue cover without fuss provided the install is properly certified, and we give them the documentation they need.

The EPC uplift is a useful by-product worth documenting, typically enough to move a band D to a C or a band C to a B, and we provide the post-install EPC and certification pack so the improvement is recorded against the asset rather than lost. Grid connection is rarely the obstacle on an office: below 100 kW the simpler G98 application generally suffices with a DNO timescale of four to eight weeks, while above 100 kW a G99 application applies with a longer six to eighteen month window. Many smaller offices have single-phase supplies that limit practical PV to around 13 kW, so where a larger system is wanted we factor a three-phase upgrade into the feasibility study rather than spring it on you later. We are MCS certified for commercial work, NICEIC registered, and RECC and TrustMark licensed, so the install satisfies both your insurer and any future buyer's surveyor.

How we approach this kind of project

We model every office from your half-hourly meter data rather than a generic per-square-metre estimate, because the gap between an optimistic guess and the real load curve is where most disappointing solar projects come from. We size for self-consumption first, so the system matches what the building genuinely uses through the working day, and every claim we make on generation or payback is backed by PVSyst modelling that we share with you rather than keep behind the curtain. We check the roof build-up and any asbestos before we quote, not on the day of the install, so the fixed price you receive is a price we can stand behind.

Where the system sits below 100 kW we submit the simpler and faster G98 grid application early, so the connection is not the thing that holds the project up, and on larger offices we start the G99 application alongside the survey for the same reason. From contract to a commissioned office system is typically eight to sixteen weeks, with the physical install taking one to four weeks and the DNO connection usually the long pole. You receive a fixed-price proposal, a clean handover pack for your accountant, and the option of a lobby touchscreen or web dashboard showing live generation, lifetime kWh and CO2 saved, which many firms put in front of visitors or on their website. The workmanship is covered by a 10-year insurance-backed warranty and the panels by a long-term output warranty.

An illustrative example

As an illustrative composite based on typical office projects: a 45-person professional services firm operating from a converted commercial unit, paying around £18,000 a year for power and wanting a visible sustainability commitment for client meetings, installed roughly 75 kW across the roof, about 138 panels with a single inverter, generating in the region of 68,000 kWh a year. The project was funded by asset finance over six years and was cash-flow positive from month one, a lobby display showed live generation to every visitor, and the EPC uplift supported the building's lettable value. The system was used as evidence in several client pitches in its first year. The payback worked out close to 6.5 years. The figures are illustrative and depend on your building, tariff and roof.

If your premises mix office space with retail or light industrial use, our pages on solar for mixed-use commercial buildings and light industrial units may also apply. When you are ready, see the cost guide, check the grants and funding routes, request a free feasibility from your meter data, or read the commercial solar FAQs first.