Commercial solar installation — what gets done, by whom, in what order.

We are an independent, commission-free commercial-solar funding specialist — we sell no installs and take no installer commission, so we can publish the numbers the installer brands ranking around us leave out. Below: the actual 2026 cost per kWp, what funding is genuinely open (and what is now closed), a neutral cross-supplier export-rate table, and a transparent payback build-up. Then the full eight-phase install process with real DNO timelines.

How much does commercial solar installation cost in the UK (2026)?

Indicative 2026 turnkey commercial solar installation costs £540–£1,100 per kWp installed. The headline rate falls as the system scales: small sub-50kWp arrays sit at the top of the range, while 1MW-plus projects fall toward £540–£620/kWp. The common 250–500kWp commercial band runs £660–£760/kWp. Crucially — and this is the figure no installer page around us prints — after the Annual Investment Allowance (a ~25% effective tax saving) and 0% VAT, the effective cost lands near 60% of the headline.

Indicative 2026 turnkey ranges including panels, inverters, mounting, DNO connection, design, install, commissioning and an insurance-backed warranty. Effective cost assumes the Annual Investment Allowance (≈25% effective tax saving) and 0% VAT on a qualifying install; your actual relief depends on tax position. See our full commercial solar cost breakdown.

Commercial solar installation cost by mount type

The single biggest cost variable after scale is how the system is mounted. Rooftop is the default and cheapest because there is no land cost; ground-mount buys the best orientation and the highest yield; a solar carport carries a clear steel-canopy premium but unlocks dual-use car-park land and an EV-charging tie-in.

Indicative 2026 ranges; ground-mount and carport figures exclude land and any abnormal groundworks or DNO reinforcement.

Funding a commercial solar installation — what is open in 2026

This is the part the installer pages ranking around us either skip or reduce to a single self-serving line. The honest 2026 picture: in England the funding is capital-allowance-led, not a cash grant — Full Expensing and AIA do the heavy lifting, alongside 0% VAT. Cash grants exist but are nation- and sector-specific, and several once-headline schemes are now closed. There is no “FETF 40%” solar grant — that figure is a persistent myth. Grants run roughly 25–40% by nation where they apply.

Indicative 2026 status; grant windows open and close and are administered locally, so always confirm current eligibility. AIA and the special-rate first-year allowance are tax reliefs claimed through your return; cash grants (REPF, Scottish/Welsh/NI/regional) are competitive and time-limited. See our commercial solar grants & funding and REPF rural funding pages.

What you will earn exporting — 2026 business export rates compared

Exported electricity is income under the Smart Export Guarantee (SEG), not a grant — and unlike the installer pages that only ever mention their preferred tariff, we compare across the market. The column that matters for a commercial operator is whether the rate forces you onto that supplier for import too. Since Octopus cut Outgoing Fixed from 15p to 12p on 1 March 2026, the leading flat rates have converged at roughly 12p — Octopus Outgoing Fixed, EDF Export 12M Small Business and Scottish Power SmartGen+ — so the flat tier is now effectively a three-way tie and the deciding factor is the import condition rather than the headline pence. EDF is the switch-free option at that level. The highest overall returns still come from the dynamic tariffs, where peaks reach around 30p, but only on sites with battery storage to shift export into those windows.

Indicative 2026 rates for comparison, verified July 2026 (Octopus Outgoing Fixed was cut from 15p to 12p on 1 March 2026); confirm current figures with each supplier. SEG floor: licensees with 150,000+ customers must offer a rate above 0p, and the system must be MCS-certified, under 5MW, with half-hourly export metering. See our full SEG comparison, Octopus SEG and EDF SEG pages.

Commercial solar installation payback — a worked example

Competitors assert “5 years” or “5–10 years” but never show the arithmetic. Here is the full build-up for a representative 250kWp rooftop install on a daytime-load commercial site, post-relief:

• System size: 250 kWp · annual generation ≈ 220 MWh (≈880 kWh/kWp)
• Self-consumed: 70% (154 MWh) avoiding grid import at 28p → £43,120/yr saved
• Exported: 30% (66 MWh) at an indicative 12p SEG → £7,920/yr income
• Total annual benefit: ≈ £51,040/yr
• Headline capex: £180,000 (≈£720/kWp) · effective capex after AIA + 0% VAT ≈ £108,000
• Simple payback on effective capex: ≈ 2.1 years on a high self-consumption site; on a 50% self-consumption profile, closer to 4–6 years

Honest sidebar: the headline payback hinges on self-consumption. The fast figure above assumes 70% of generation is used on site, displacing 28p import — realistic for a warehouse, factory or office with strong weekday daytime load. A site that exports most of its generation earns the SEG rate instead of avoiding 28p, so payback stretches toward the upper end. Across typical UK commercial profiles, post-stack payback is 4–6 years with a 25-year-plus asset life. We model your actual load curve and the funding stack together rather than quoting a single optimistic number.

How is commercial solar installed? The eight-phase process explained

The visible step-by-step below is also marked up as HowTo structured data, so search engines can read the install sequence directly. Full real-world DNO timelines are carried through — something none of the ranking installer pages publish.

The eight phases of UK commercial solar installation

Phase 1 — Site survey & structural assessment (week 1-2)

Engineers visit the site to confirm roof condition, structural capacity (PV adds 12–15 kg/m² to the roof load), shading, orientation, and electrical infrastructure. Pre-2000 portal-frame buildings often need additional purlin or bracing — we get a structural engineer's report at this stage. Output: detailed site survey report, structural sign-off, design constraints map.

Phase 2 — Electrical design & DNO application (week 2-4)

The electrical design specifies inverter sizing, AC infrastructure, switchgear, isolation points, and the connection method. The G99 application is then submitted to the local DNO (UK Power Networks, NGED, Northern Powergrid, SP Energy Networks, ENWL, or SSEN — depending on region). G99 turnaround is 60-110 working days. This is the long pole of the project — submitted week 4 latest, ideally week 1.

Phase 3 — MCS-compliant system design (week 3-5, parallel to Phase 2)

System design is finalised under MCS commercial standards. PVsyst modelling produces the yield assessment. Panel and inverter selection — Tier 1 modules (Trina, JA Solar, Jinko, Longi) and commercial-grade inverters (SMA, Huawei, Sungrow, Solis). Mounting structure (Schletter, K2, Van der Valk for rooftop; ground-mount for land arrays).

Phase 4 — Procurement & supplier contracts (week 5-7)

Supplier orders placed for panels, inverters, mounting, DC cabling, AC switchgear. Major lead times: inverters (2-6 weeks for commercial sizes), specialised mounting systems (3-5 weeks). For PSDS or Local Growth Fund projects, procurement runs through public-sector frameworks. For private projects, direct supplier engagement.

Phase 5 — DNO connection works (week 8-12, parallel)

If the DNO Connection Offer requires non-contestable network reinforcement (transformer upgrade, substation works, 11kV reinforcement), the DNO completes that work. Lead times for transformer upgrades have been 6-14 months globally in 2025-26 — confirm at G99 stage.

Phase 6 — Panel install & mounting (week 8-12)

On-site install. For sub-500kWp rooftop projects, typically 1-2 weeks of install time using IPAF-trained technicians and a small crew (2-4 installers). DC infrastructure is built up panel-by-panel as the array goes on. Health and safety follows CDM 2015 — site-specific RAMS.

Phase 7 — Inverter & AC connection (week 12-13)

Inverters mounted in plant room or external enclosure. AC switchgear installed and tested. Final commissioning electrical certification (NICEIC) completes the AC side. The DNO supplies the energisation date based on G99 schedule.

Phase 8 — Commissioning, MCS sign-off, M&V setup (week 13-16)

System energised, performance test against PVsyst yield model. MCS commercial certification issued. Insurance-backed warranty registered. Monitoring system (SolarEdge, Solar-Log, Huawei Smart PV, Sungrow iSolarCloud) set up with daily / monthly reporting. Handover documentation pack completed. Annual O&M plan in place.

Who actually does the installation

We don't install ourselves. We project-manage the build through one of six MCS-certified delivery partners across the UK:

• South East & London — partner installer covering UKPN territory
• South West & Wales — partner covering NGED Wales/SW
• Midlands — partner covering NGED Midlands
• North West — partner covering ENWL territory
• North East & Yorkshire — partner covering NPG territory
• Scotland & Northern Ireland — partners covering SP Energy Networks and NIE Networks territories

Each partner is an MCS-certified commercial installer with NICEIC or equivalent electrical certification. We hold one contract on behalf of the client; the delivery partner does the install. This keeps procurement clean and gives us 6+ years of relationship-based delivery quality data per partner.

What you should expect from your installer

Five things to confirm at quote stage:

1. MCS commercial certification — non-negotiable for grant routes and SEG eligibility
2. Insurance-backed warranty (IBW) — separately listed on quote
3. G99 DNO confirmation — pre-application response in writing before contracts
4. Itemised cost breakdown — panels + inverters together should be 50-55% of total quote
5. 0% VAT applied — explicit ask, some installers default to charging 20%

How to choose a commercial solar installer — the full vetting checklist

This is a high-intent decision query the installer pages around us never answer honestly — because they are the installer. As an independent funding specialist with no install to sell, here is the neutral due-diligence list we run for clients before any contract is signed:

1. MCS 020 commercial certification — confirm the firm holds the commercial MCS standard (not just domestic), because it gates grant eligibility and SEG. Ask for the certificate number and check it on the MCS register.
2. Insurance-backed warranty (IBW) — a workmanship warranty is worthless if the installer folds. An IBW (e.g. via a recognised scheme) must be listed separately on the quote, not bundled into a vague “guarantee”.
3. G99 pre-application in writing — the installer should obtain and share a written DNO G99 pre-application response before you sign, so the connection position (and any reinforcement cost) is known, not assumed.
4. Itemised quote — panels and inverters together should be roughly 50–55% of the total. A quote that is one round number with no breakdown is hiding either thin margin on hardware or fat margin on labour.
5. Explicit 0% VAT line — the qualifying-install 0% VAT rate must be stated; if the quote shows 20%, challenge it before paying.
6. References for similar-sized installs — a firm comfortable on 30kWp domestic-scale arrays is not automatically right for a 500kWp three-phase commercial connection. Ask for two references at your system size and roof type.

Best route for your commercial solar installation — our verdict

For a finance-director buyer weighing the install in 2026, here is the ranked call we give clients, neutral and commission-free:

1. Best overall value — rooftop, 250–500kWp band, funded on AIA + 0% VAT. Lowest £/kWp with land already owned, effective capex near 60% of headline, and a 4–6 year post-stack payback. This is the default winner for most commercial sites with a usable roof and daytime load.
2. Best for rural & farm businesses — rooftop or ground-mount with a REPF grant application. Where a participating English local authority window is open, REPF (up to 40%) stacks on top of the capital allowances; Scottish, Welsh and NI businesses have their nation-specific routes.
3. Best for car-park sites & EV-forward operators — solar carport. Higher £/kWp from the steel canopy, but it monetises otherwise dead car-park land and pairs with EV charging — worth the premium only where rooftop space is genuinely exhausted.
4. Best for the public sector — Salix-funded rooftop. Schools, NHS sites and councils route through Salix rather than the corporate tax reliefs, which do not apply to them.

The common thread: the install is the easy part — the funding stack and export-tariff choice decide the return, and that is exactly where an independent specialist earns its place.

Commercial solar installation by sector

Installation considerations and the best funding route differ sharply by property type. These sector cut-throughs cover the specifics — roof structure, load profile, procurement framework and applicable funding:

• Warehouse & distribution solar installation — vast roof area, light daytime load, high export share; the classic SEG-revenue play.
• Retail solar installation — strong daytime self-consumption from refrigeration and lighting.
• Agricultural & farm solar installation — big sheds, rural REPF eligibility, seasonal demand.
• Office solar installation — strong weekday load, low weekend demand.
• School solar installation — Salix-funded, procurement-framework routed, term-time load profile.
• Manufacturing & industrial solar installation — heavy continuous load, ideal self-consumption, Scottish IETF where applicable.