Public sector: Commercial Solar PV

Why commercial solar PV suits the public sector and education

Public buildings are among the strongest candidates for commercial solar PV in the UK, and the reasons are structural rather than incidental. Schools, hospitals, leisure centres, libraries and council estates tend to occupy exactly the buildings solar was designed for: large single-storey or low-rise roofs, wide unshaded spans, and a demand pattern that runs through the working day. When a building draws most of its power between 09:00 and 16:00, generation and consumption line up almost perfectly, and that alignment is the single biggest driver of a good payback.

There is also a funding advantage that the private sector does not have. Public bodies can access Salix interest-free finance and the Public Sector Decarbonisation Scheme, which are designed specifically to fund solar and wider decarbonisation across the public estate. That changes the arithmetic. A private company weighs capex against payback; a school or NHS trust can often deploy solar with no capital outlay at all, repaying an interest-free loan out of the bill saving it creates.

The estates involved are frequently large and repeatable. A multi-academy trust, an NHS foundation trust or a county council owns dozens or hundreds of buildings, and an estate-wide rollout unlocks procurement scale that a single-site owner never sees. Standardising the design, the mounting system and the monitoring platform across a portfolio drives down the per-building cost and simplifies the maintenance regime for years afterwards.

For a public building the case rests on four features, and each one deserves unpacking:

• Large roofs and strong daytime demand. Schools, hospitals, leisure centres and council offices carry substantial roof area and consume power precisely when the sun is up. That combination is what makes self-consumption high and export low, which is where the value sits.
• Sector-specific funding. Salix interest-free finance and the Public Sector Decarbonisation Scheme can fund public buildings directly, a route that is not open to private business.
• Term-time and opening-hours demand aligns with generation. A building that operates during daylight hours consumes most of what it generates without needing a battery, keeping the capital cost down.
• Estate-wide rollouts unlock scale. Deploying across a MAT, trust or authority spreads fixed costs and turns a series of small projects into one economically efficient programme.

Beyond the economics, public bodies carry statutory and reputational pressure to decarbonise. Local authorities have declared climate emergencies and set net zero target dates; the NHS has a published net zero commitment; schools answer to parents, governors and pupils who expect leadership on sustainability. Solar is the most visible, most measurable step a public building can take, and unlike many decarbonisation measures it pays for itself.

The electricity load profile and self-consumption

Getting the economics right for a public building starts with understanding how it actually uses electricity through the day, week and year. A well-designed system is sized against that shape, not against roof area alone.

Most public buildings are daytime-weighted. A primary school draws its heaviest load during the teaching day, tapering after 16:00 and largely dormant at weekends and through the summer holidays. A leisure centre with a pool runs a long, heavy day driven by pumps, filtration, lighting and HVAC. A hospital is the exception that proves the rule: it operates round the clock, so its baseload never falls to zero and its self-consumption of solar is exceptionally high because there is always demand to absorb the generation.

Self-consumption is the number that matters. It is the proportion of what the panels generate that the building uses on site rather than exporting to the grid. On-site power displaces electricity you would otherwise buy at 25p to 45p per kWh; exported power earns a Smart Export Guarantee tariff of roughly 4p to 15p per kWh. The difference is large, so a good design maximises the share consumed on site.

A daytime-occupied public building with 09:00 to 18:00 use typically achieves 55% to 75% self-consumption without any battery. That figure climbs for buildings with continuous demand and falls for buildings that empty out in the evening. The two features that pull it down in this sector are worth naming plainly. First, term-time patterns: a school generates strongly through July and August when it is closed, so a meaningful slice of summer output is exported rather than used. Second, weekend closure: an office-style council building sits idle on Saturdays and Sundays while the panels keep producing.

The design response is to size the system so that its annual generation matches roughly 60% to 85% of consumption. That target keeps self-consumption high and avoids building an oversized array that dumps low-value surplus onto the grid. Where evening, weekend or holiday demand is significant, battery storage becomes worth modelling. A battery lifts self-consumption toward 80% to 95%, and above about 100 kWp, or where there is real out-of-hours load such as a pool or a data room, we model the system both with and without storage so the decision is made on numbers rather than assumption.

System sizing for public and education buildings

Public-sector and education systems in the UK typically fall in the 50 kW to 500 kW range, using around 92 to 920 panels across roughly 300 to 3,000 square metres of roof. Those are broad bands because the sector spans a single-form-entry primary school at the small end and a large acute hospital or multi-site leisure trust at the large end. The sizing is driven by consumption and available roof, not by a fixed template.

The engineering rule of thumb is straightforward. One kilowatt-peak of PV occupies about 5 to 6 square metres of unshaded roof and generates roughly 900 to 1,000 kWh a year in the UK climate. So a 300 square metre roof supports on the order of 50 kWp, and a 3,000 square metre roof can carry close to 500 kWp before other constraints bind. In practice the limiting factor is often not roof area but the grid connection or the building's own annual consumption, since there is little point installing an array so large it exports most of what it makes.

Annual generation across the sector's typical range runs from about 46,000 kWh at the small end to around 460,000 kWh at the large end. In carbon terms that displaces roughly 10 to 106 tonnes of CO2 a year, a figure that feeds directly into a public body's Scope 2 emissions reporting and net zero tracking. For a school or trust that has to demonstrate progress against a declared target, that measured, auditable reduction is as valuable as the bill saving.

We size every system from half-hourly meter data rather than a per-square-metre estimate. Half-hourly data reveals the real shape of demand: the morning ramp, the lunchtime peak, the after-hours baseload, the summer trough. That is what tells us whether a 120 kWp array with no battery or a 200 kWp array with 100 kWh of storage is the better fit, and it is why the same roof can justify very different systems for two buildings that look identical from the street. You can model the trade-offs yourself using our savings calculator, and we confirm the design with a full yield model before any proposal is issued.

A worked cost and payback example

Public-sector and education projects in this range typically carry a project value of around £45,000 to £425,000, tracking system size across the 50 kW to 500 kW band. Payback in this sector is typically about 7 years, sitting slightly above the fastest-paying industrial installs because term-time and weekend closures mean a portion of generation is exported rather than self-consumed.

Take a mid-sized secondary school as a worked example. Assume a 150 kW system on a large flat and shallow-pitch roof, costing in the region of £135,000 before any tax treatment or funding. At UK yields that array generates roughly 138,000 kWh a year. With a daytime teaching load absorbing most of it during term time, self-consumption sits around 65%, so the school directly displaces grid power it would otherwise buy at commercial rates, and exports the summer and weekend surplus under a Smart Export Guarantee tariff.

The combination of avoided purchase and export income produces an annual benefit that, against a £135,000 outlay, lands the payback close to the sector-typical 7 years. After payback the panels keep producing under their 25-year performance warranty, delivering something in the order of 15 to 18 further years of near-free generation. The table below sets out the shape of that example.

Parameter	Worked example (150 kW secondary school)
System size	150 kW, roughly 275 panels
Roof area used	Approximately 800 to 900 sqm
Indicative project value	In the region of £135,000
Annual generation	Around 138,000 kWh
Self-consumption	Approximately 65% (term-time daytime load)
Typical payback	About 7 years
Warranty	25-year panel performance, 10-year IWA workmanship
CO2 saved per year	Roughly 30 tonnes

The figures above are indicative and depend on tariff, roof orientation, shading and the exact demand profile. For a firmer picture across a range of building sizes, see our detailed cost and payback guide, which breaks down real per-kWp pricing and what is and is not included in a fixed-price proposal.

Planning, compliance and grid connection

Public and education buildings carry a compliance layer that private commercial sites do not, and it pays to plan for it rather than discover it mid-project.

The first consideration is procurement. Public bodies are bound by public procurement rules, so the works usually have to be let through an established framework or a formal tender rather than a simple direct award. That governs how a contractor is appointed and adds lead time at the front of the programme. We are comfortable operating through framework calls-off and competitive tenders, and we build the procurement route into the project timeline from the start.

The second is safeguarding. Any on-site works at a school or college trigger safeguarding and DBS requirements for the personnel involved. Installers working on an occupied education site must satisfy the same checks as any other visiting contractor, and works are commonly phased around term dates, with the bulk of the roof work carried out during holidays to minimise disruption and safeguarding exposure.

The third is the roof itself. Before any design work begins, the roof condition and its remaining warranty life should be confirmed. There is no sense mounting a 25-year asset on a covering with five years left in it, and a public body will rightly expect that question answered up front. Where a roof is nearing the end of its life, the economics of re-roofing and installing solar together are usually far better than doing them separately.

On planning, most commercial and public rooftop PV falls under Permitted Development, Class A Part 14 of the GPDO 2015, subject to size and siting limits. Listed buildings, which are common in the public estate, need Listed Building Consent for visible arrays, and conservation-area or street-facing installations often need a full planning application. We confirm the planning route as part of the feasibility study and handle any application required.

Grid connection is the item most likely to set the overall timeline. Small systems can use the faster G98 or G99 fast-track, but most public-building systems in the 50 kW to 500 kW range need a full G99 application to the Distribution Network Operator. For larger arrays, export limitation under G100 is often used to secure a connection quickly and avoid costly network reinforcement. Timescales run from around 4 to 12 weeks for small connections up to 6 to 18 months for larger ones, so the G99 application goes in early, usually before the site survey, because it is almost always the critical path.

Two further regulatory points apply across the sector. Buildings constructed before 2000 need an asbestos management survey before roof works begin, which is common in the older parts of the public estate. And larger installs fall under CDM 2015 for the construction phase, with the attendant duties on the client and the principal contractor. Both are routine when planned for and disruptive when they are not.

Funding routes that fit this sector

Public bodies have access to funding that private business does not, and choosing the right route materially changes the project economics. The primary channels are these:

• Public Sector Decarbonisation Scheme (PSDS) and Salix. PSDS and Salix funding is the main route for public buildings, offering grant funding and interest-free loans that cover solar alongside wider decarbonisation. It is applied for centrally by the public body itself rather than by the installer, so the enquiring school, trust, NHS body or council makes the application. This is the single most important lever in the sector, because an interest-free loan repaid from the bill saving can make a project effectively self-financing.
• Smart Export Guarantee (SEG). The SEG pays for surplus exported to the grid, typically 4p to 15p per kWh depending on tariff and supplier. Because public buildings such as schools and offices export a meaningful share of summer and weekend generation, a competitive SEG tariff is a real part of the economics rather than an afterthought.
• Regional and combined-authority grants. Some combined authorities and Growth Hubs periodically run decarbonisation grant rounds that public and voluntary-sector bodies can access. These open and close, so it is worth checking the current position before committing to a route.

Where a body cannot or does not want to fund capital directly, a Power Purchase Agreement remains an option in principle: a funder installs and owns the system and the building buys the power at a fixed rate below grid. In the public sector, however, the interest-free and grant routes usually beat a PPA on lifetime cost, so we model the alternatives side by side and recommend the one that leaves the most value with the public purse. For a full breakdown of every scheme and how to apply, see our grants and funding routes.

A representative project scenario

Consider a three-form-entry secondary school within a multi-academy trust in the Midlands, occupying a mix of flat-roofed teaching blocks and a sports hall, with an annual electricity spend of around £62,000. Rising commercial tariffs had eaten into the school's operating budget year on year, and the trust wanted a measure that both cut cost and demonstrated progress against its declared net zero commitment.

Modelling from the school's half-hourly meter data showed a strongly daytime-weighted load during term time, with predictable troughs at weekends and through the summer break. The design settled on a 160 kW array of around 295 panels across roughly 900 square metres of teaching-block and sports-hall roof, generating in the order of 148,000 kWh a year. Self-consumption came out at about 63%, held down by the summer holiday export, and the balance was placed on a competitive Smart Export Guarantee tariff.

The trust funded the project through an interest-free Salix loan applied for centrally, so the school carried no upfront capital cost and repaid the loan out of the electricity saving it generated. The G99 application went in ahead of the site survey and cleared inside the connection window, and the roof works were phased into the summer holidays to sit clear of teaching and safeguarding constraints. The result was a payback broadly in line with the sector-typical 7 years, an annual carbon reduction of roughly 32 tonnes feeding directly into the trust's Scope 2 reporting, and a live generation display in the school entrance used as a teaching resource. This scenario is illustrative and not a named client; the figures are plausible for a building of this type. To model your own building, request a free quote and we will build the design from your meter data.

Common questions about commercial solar for the public sector and education

Can a school or council install solar with no upfront cost?

Often, yes. Salix interest-free finance and the Public Sector Decarbonisation Scheme are designed to fund solar on public buildings, and an interest-free loan repaid from the bill saving can make a project effectively self-financing with no capital outlay. The funding is applied for centrally by the public body rather than by the installer, so the school, trust, NHS organisation or council makes the application. Where those routes are not available, a Power Purchase Agreement needs zero capex, though in the public sector the grant and interest-free options usually beat a PPA on lifetime cost.

What is the payback on solar for a public building?

Typical payback in this sector is about 7 years, slightly longer than the fastest industrial installs because term-time and weekend closures mean a portion of generation is exported rather than used on site. A hospital or leisure centre with continuous demand pays back faster because it self-consumes more; a school that closes for the summer holidays sits at the higher end. The panels carry a 25-year performance warranty, so after payback the system delivers 15 to 18 further years of near-free power. We give you the full figures, including the effect of any interest-free funding, rather than a single headline number.

How does the summer holiday affect solar on a school?

It reduces self-consumption but does not undermine the case. A school generates strongly through July and August when it is largely closed, so a meaningful slice of summer output is exported rather than used on site, earning the Smart Export Guarantee tariff rather than displacing purchased power. We account for this directly in the modelling by sizing the array against the real term-time demand shape and, where it improves the economics, by considering battery storage to shift some generation into occupied hours. The seasonal pattern is why school payback typically sits at the upper end of the 5 to 8 year commercial range.

Do we need to worry about procurement rules and safeguarding?

Yes, and both are routine when planned for. Public procurement rules usually mean the works are let through an established framework or a formal tender rather than a direct award, which we build into the timeline. On education sites, safeguarding and DBS requirements apply to everyone working on site, and roof works are commonly phased around term dates so the bulk of the disruption falls in the holidays. We are set up to satisfy both, and we confirm the procurement route and the safeguarding arrangements before any works begin.

Will solar work across a whole trust or council estate rather than one building?

Estate-wide rollouts are where the public sector sees the strongest economics. Deploying across a multi-academy trust, an NHS trust or a local authority spreads fixed costs and unlocks procurement scale, and standardising the design, mounting and monitoring across the portfolio drives the per-building cost down. We assess each roof on its own merits, because a building only warrants an array where the roof, load profile and grid connection support it, then sequence the programme so the strongest sites go first. If your estate spans warehouses or offices as well, our work on warehouses and industrial units and offices applies the same modelling discipline to those building types.