Secondary Schools: Solar panels for schools

Why a secondary school changes the economics

A secondary school is where school solar starts to look like a serious commercial project, and the reason is load. Where a primary is a single small building that empties in the holidays, a secondary is a varied estate — a main teaching block, a sports hall, a science block, sometimes a separate sixth-form or arts building — with a much heavier and steadier daytime baseload. IT suites, science labs, catering kitchens, ventilation and lighting run all through the teaching day, and that changes everything about self-consumption. A secondary consumes far more of what its roof produces than a primary ever will, which is why the payback is shorter even though the system is bigger.

Typical secondary systems run 100 to 300 kW using around 185 to 550 panels across 600 to 1,800 square metres of roof. They generate 92,000 to 275,000 kWh a year and save 21 to 63 tonnes of CO2 annually. Project values sit in the £90,000 to £270,000 band, with a payback around 6.5 years — quicker than a primary precisely because the daytime load soaks up more of the generation on site rather than exporting it. A typical secondary now spends £80,000 to £250,000 a year on grid electricity, so displacing even a third of that is a five- or six-figure recurring saving straight back into the teaching budget.

The varied roof estate and how we read it

A secondary's varied roof estate is an opportunity, not a complication, if it is handled well. Different buildings have different roof types, orientations, ages and structural capacities — a 2000s Building Schools for the Future block behaves very differently from a 1960s system-built teaching wing or a Victorian original. Some flat membrane roofs take a dense ballasted array with no penetrations; some pitched slate roofs on older blocks are structurally marginal and need reinforcement or exclusion. Part of a proper secondary feasibility study is a building-by-building read of the estate: which roofs are strongest, which face south, which sit over the heaviest daytime loads, and which should be left out entirely. That read is what lets us design an array that is bigger than a primary's but still genuinely fits the buildings it sits on.

Phased, multi-building delivery

Because the estate is varied, we usually phase secondary installs across more than one building and more than one holiday window. We prioritise the buildings with the best roof condition, orientation and load match first, prove the model on those, then extend across the estate. Phasing lets a school spread capital across financial years, align each phase with a school-holiday window rather than trying to do everything in one summer, and adjust later phases in light of what the first phase's real generation data shows. A single-building install can sometimes be completed in one summer break; a full-estate programme is almost always better delivered in stages.

Exam-season exclusion — the scheduling rule that defines a secondary

The single most important scheduling constraint at a secondary is the GCSE and A-level exam season. From roughly early May to late June, heavy works — scaffolding, roof access, noisy plant, deliveries near exam halls — are effectively excluded. A specialist plans the whole programme around this window; a generalist books the crew for June and finds the school will not let them on site. We treat the exam period as a hard no-go zone and design the delivery schedule backwards from it, concentrating disruptive work in the Easter and summer holidays and keeping the exam term clear. Site induction by the SBM is mandatory before any crew starts, and the same DBS and KCSIE 2025 safeguarding standards apply throughout: DBS clearance to Enhanced level including the Children's Barred List, escorted access in pupil areas, sign-in/out, and holiday scheduling for anything disruptive. Ofsted-window awareness and Friday-evening or INSET-day commissioning round out the scheduling discipline that keeps a live secondary running normally throughout.

A worked example

Take a secondary academy facing electricity costs that have climbed from around £85,000 to £170,000 across two years, with a growing roll and a board-level net-zero commitment. The main teaching block offers roughly 950 square metres of flat membrane roof. A 118 kW system of about 218 panels across two inverters generates in the region of 108,000 kWh a year. Because the school runs a busy daytime IT and catering load, self-consumption holds high without any battery, and annual savings land near £26,000 for a payback around 6.2 years. Funded 100 per cent through an interest-free Salix Decarbonisation Loan, the project is cash-flow positive in year one. A live-generation display goes into the entrance and, as happens time and again, the strong first result gets the remaining phases approved at the next governors' or trustees' meeting.

Funding a secondary project

The Salix Decarbonisation Loan remains the workhorse route for a maintained secondary or a secondary academy: interest-free, repaid from savings, cash-flow positive from day one. But at secondary scale the capital-grant routes come into their own. The Public Sector Decarbonisation Scheme can fund up to 100 per cent of eligible measures and is strongest when solar is paired with heat decarbonisation across the estate. Academy secondaries and voluntary-aided schools can bid into the Condition Improvement Fund, which scores well when PV rides alongside a planned roof refurbishment on one of the older blocks — a natural fit when you are phasing across a mixed estate anyway. Devolved Mayoral Combined Authority schemes can add regional funding in some areas. We map the right combination for your status and write the auditable savings calculation each scheme requires. The full detail is on our grants and funding page.

Self-consumption and the battery decision

Because a secondary's daytime baseload is high, the battery decision is less clear-cut than at a primary. Many secondaries hit strong self-consumption on solar alone and do not need storage to justify the project. Where a battery does earn its place, it is usually to capture the summer-holiday surplus rather than to shift a term-time shortfall — a smaller and more targeted role than in a primary. As always, we size from at least twelve months of your half-hourly meter data including a holiday period, so the battery recommendation reflects your actual demand curve rather than a rule of thumb. Larger secondary arrays sit above 17 kW per phase and so need a G99 grid application, which we run end to end alongside the structural and asbestos surveys.

Can you fit the whole system in one summer holiday?

Sometimes, for a single-building install. For a full estate we usually recommend phasing across two or more holiday windows — it protects roof-condition sequencing, spreads capital across financial years, and keeps every phase clear of the May-to-June exam season. Phasing also lets you prove the economics on the first block before committing the rest of the estate, which is exactly how most of our secondary clients approach it.

Will solar interfere with our science labs, IT or catering load?

No — those loads are the reason a secondary's economics are so good. Heavy daytime consumption from labs, IT suites and kitchens is exactly what lifts self-consumption and shortens payback. The system sits behind the meter and simply reduces what you draw from the grid during the teaching day; there is no impact on how those facilities run, and no interruption to supply at commissioning beyond a brief planned switchover.

How do you work around exams?

We treat the GCSE and A-level exam season as a hard exclusion and plan the whole programme around it. Disruptive works go into the Easter and summer holidays; the exam term stays clear. This is standard for us and written into the delivery schedule from the first proposal, so there is never a clash to negotiate later.

A curriculum and reporting asset, not just an estates line

A secondary can do more with the data than a primary because the curriculum is broader. A rooftop array feeds directly into GCSE and A-level Geography, Physics, Design & Technology and the growing set of environmental-science and engineering options, and a live-generation display in reception or the main hall gives teachers a real, local dataset to work from rather than a textbook example. Sixth-form students can interrogate the half-hourly generation and consumption figures as a genuine data-analysis exercise. For the senior leadership team, the same system produces clean, auditable numbers for governor and trust-board reporting against the DfE Sustainability and Climate Change Strategy, whose milestone reductions fall in 2030 and 2035 on the way to a net-zero estate by 2050. That dual value — a teaching resource on one side, a defensible net-zero evidence line on the other — is frequently what carries the decision through a governing body that is weighing scarce capital against classroom priorities.

The grid connection is usually the long pole

On a secondary, the physical install is rarely the longest item in the timeline — the grid connection is. Any array above 17 kW per phase needs a G99 application to the local Distribution Network Operator, and on capacity-constrained parts of the network the technical study plus connection offer can run several months. We submit the G99 immediately after the structural survey so the DNO clock starts as early as possible, rather than waiting until the crew is booked, and we run the Salix or grant application in parallel. That is why the honest timeline from first call to a commissioned secondary system is typically six to nine months even though the panels themselves go up in a single holiday: the paperwork and the network, not the roof, set the pace. A specialist manages the DNO end to end so the SBM never has to learn the process; a generalist who leaves the G99 until the install is scheduled routinely loses a term to it.

Protecting a mixed-age roof estate

The varied age of a secondary's buildings makes roof protection more important here than almost anywhere. A full structural survey precedes any quote on each building we propose to use, because the load a roof can carry differs enormously between a 2000s steel-framed block, a 1960s system-built wing and a Victorian original. We use roof-warranty-compatible fixings so existing roof guarantees are preserved, favour ballasted mounting on sound flat membranes to avoid penetrations, and exclude any roof that is structurally marginal or near the end of its life rather than build on borrowed time. Pre-2000 blocks get an asbestos (ACM) management survey as standard. Every install carries a ten-year insurance-backed workmanship warranty, and once commissioned the system is monitored remotely so a faulty string or inverter across a multi-building estate is spotted and fixed before it quietly costs a term's worth of generation.

See how a whole-estate rollout across several sites is funded and phased on our multi-academy trusts page, get the numbers for your building via our free feasibility study, or read the full school solar cost guide and the routes on our grants and funding page.