75kW Commercial Solar Systems for UK Businesses

A 75 kW commercial solar system sits in a particularly interesting spot on the cost curve in 2026. It is large enough that per-kW economics start to improve meaningfully (we typically quote £900-£1,000 per kW at this scale, versus £1,000-£1,200 at 25 kW), large enough that procurement leverage on tier-1 panels and inverters is real, and small enough that 100% Annual Investment Allowance covers the entire project capex inside a single year for almost any limited company. The trade-off: at 75 kW you cross into G99 grid-connection territory, so the DNO process slows from 4-8 weeks (G98) to typically 6-12 weeks for an offer letter on uncongested networks.

The 75 kW band is what we recommend for medium-format retail (1,500-3,000 sqm sales floor — supermarkets, DIY, garden centres), large offices with 60-100 staff, light industrial units running 1-2 production lines or substantial assembly operations, mid-size hotels with 35-55 rooms, and independent or academy schools with extended-day operations. The common thread: a 450 sqm roof in serviceable condition, three-phase 200 A+ electrical supply, and daytime baseload of 18-25 kW.

What 75kW looks like physically

A 75 kW system in 2026 is built from approximately 138 tier-1 monocrystalline panels at 540-550 Wp each (Trina Vertex, JA Solar Deep Blue, Longi Hi-MO 6 or equivalent). With higher-output 600 Wp modules the count drops to around 125. You need approximately 450 sqm of usable, well-oriented roof area free of significant shading. Total array weight on a flat roof, including ballasted mounting, comes in around 18-22 kg per square metre — a chartered structural engineer signs this off as part of every quote. Electrically, the system uses one 75 kW three-phase string inverter or 2 x 40 kW units (typically Sungrow SG-CX, Solis-S6, Huawei SUN2000 or SMA Tripower CORE) connected through MCS-compliant DC and AC switchgear, with sub-string monitoring resolution and full G99 connection paperwork lodged with your DNO. SPD coordination is standard across DC, AC and signal circuits.

Cost breakdown for a 75kW install in 2026

Turnkey 2026 pricing for a properly specified 75 kW system runs £67,000-£90,000 plus VAT, working out at roughly £900-£1,000 per kW — slightly better per-kW than the smaller bands because procurement leverage and install efficiency improve at this scale. The price band includes 138 tier-1 panels at trade pricing, a commercial-grade three-phase string inverter setup (typically dual or split topology for redundancy), an MCS-spec mounting system, all DC and AC cabling, surge protection, fire-safe DC isolators, a dedicated PV consumer unit interface, half-hour-resolution monitoring with a dedicated cloud portal, scaffolding, structural sign-off from a chartered engineer, electrical sign-off, full G99 connection paperwork including Type Test certificates, and 12 months of post-commissioning support.

Where a 75 kW project goes over budget tends to be one of four known knowns: an asbestos-cement industrial roof needing licensed removal (£8,000-£25,000 at 450 sqm), three-phase headroom upgrade where the existing supply has limited spare capacity (£5,000-£12,000 to the DNO), DNO reinforcement charges if the local network is constrained (£0-£25,000), or roof reinforcement (£3,000-£15,000 depending on extent). We identify these at survey stage and quote them clearly. We do not bury them in vague site-prep entries.

On AIA: 100% Annual Investment Allowance covers the full capex up to the £1m annual cap. A £78,000 install reduces a profitable limited company's corporation tax bill by £19,500 in year one (at the 25% main rate). That drops the effective net cost to roughly £58,500 before counting energy savings. The Land Remediation Tax Relief recovers an additional 50% of any asbestos-removal element through corporation tax. We coordinate with your accountant on the year-one tax computation and frequently roll asbestos remediation and PV install into a single project to maximise allowance stacking.

Generation and savings

A typical UK 75 kW system generates 67,000-70,000 kWh in year one. We model this in PVSyst with site-specific Meteonorm 8.2 irradiation data, panel temperature derating, inverter clipping where relevant, and shading losses derived from Lidar-resolution 3D modelling. Self-consumption is the dominant driver of project economics. A 75 kW system on a continuous-baseload site (24/7 retail with chiller load, mid-size hotel with year-round occupancy, multi-shift light industrial) typically achieves 80-88% self-consumption. On a single-shift business or 9-5 office, self-consumption drops to 65-75%. The difference between 70% and 85% on a 75 kW system is roughly £3,200 of additional annual benefit.

At 75% self-consumption with a 24p/kWh blended import price, a 75 kW system avoids around £12,400 of grid energy purchases per year. The remaining 17,000 kWh exports to grid at the SEG rate. At a blended 6p/kWh SEG rate that adds £1,020 of export income, taking total year-one benefit to around £14,000-£18,000. Simple payback on £78,000 capex (or £58,500 net of AIA) lands at 6-6.5 years. 25-year IRR is 13-16% and 25-year NPV at a 7% discount rate is approximately £255k-£325k.

DNO grid connection — G99 timing matters

Above 50 kW per phase you cross into G99 territory (formally ENA Engineering Recommendation G99) which requires a full Connection Application to your DNO before commissioning. Standard DNO turnaround for a 75 kW offer letter in 2026 runs 6-12 weeks on uncongested networks, sometimes longer in constrained network areas. The application costs £350-£1,500 to file. Around 70% of 75 kW G99 applications get a standard offer with no reinforcement charge; the remainder face contributions ranging from £2,000 to £25,000+ for transformer or upstream cable upgrades. Our process: file the G99 application within two weeks of contract signature, run design and procurement in parallel, time delivery to site for the week the connection offer is accepted. If reinforcement comes back high, we re-engineer to stay below the threshold (export limiting or downsizing to 49.9 kW per phase) and re-file before any capex commits.

Best-fit sectors for the 75kW band

From our 2025 install book, the 75 kW band overweighted across five sub-verticals. Medium-format retail (1,500-3,000 sqm sales floor — independent supermarkets, DIY, garden centres, B&M-style discount chains) where chiller load and lighting drive high self-consumption. Large offices with 60-100 staff in self-occupied freehold light-industrial units (decent daytime load, predictable hours, ample roof). Light industrial units running 1-2 production lines or substantial assembly operations (food processing, light manufacturing, packaging). Mid-size hotels with 35-55 rooms where year-round occupancy, kitchen, laundry and HVAC drive consistent demand. Independent and academy schools with sports halls, kitchens and ICT load running through extended-day operations. These map cleanly to our coverage of medium SME sectors.

Worked example: a Lincolnshire independent supermarket, 8,500 sqm site of which 2,200 sqm is sales floor, 480 sqm of usable roof on the main retail building, three-phase 400 A supply, 24/7 chiller load, 280,000 kWh annual consumption. Quoted £77,500 plus VAT for 74.9 kW (138 x 545 Wp JA Solar panels, Sungrow SG75CX inverter, K2 ballasted east-west mounting). Modelled year-one yield 68,400 kWh. Self-consumption modelled at 86% (chiller load runs continuously, well-matched to PV curve), so 58,800 kWh avoid the grid at 25p/kWh blended (£14,700 saved) and 9,600 kWh export at 6p/kWh SEG (£576). Total year-one benefit £15,276. AIA tax relief £19,375. Simple payback 5.1 years, 25-year IRR 17.4%.

Financing a 75kW system

Three financing routes work at 75 kW scale. Cash plus AIA delivers the strongest IRR for any limited company with corporation tax exposure — the £19,500 year-one tax relief shortens payback by around 18 months versus a finance route. Asset finance over 5-7 years (around £1,300-£1,560 per month over six years on £78k capex) is the route most of our 75 kW SME customers actually choose: the monthly finance payment is consistently lower than the monthly bill saving, project is cash-flow positive from month one, working capital stays in the business. Hire purchase preserves AIA; an operating lease forfeits it. PPA structures begin to make sense at 75 kW for businesses with limited corporation tax exposure — a 15-year fixed-rate PPA at 12-15% below current grid retail with end-of-term ownership transfer is achievable, but cash and asset finance still dominate at this scale because the third-party setup costs dilute returns. We model all three routes in your finance options assessment, and our grants and funding guide covers any sector-specific schemes that apply.

Next steps

If you want to know whether a 75 kW system makes sense for your specific business, the fastest route is a free desk-based feasibility against your half-hourly meter data — turnaround is five working days. Request a quote with your address and we'll come back with a draft yield, financial model and grid feasibility before you commit. For broader cost benchmarking across system sizes see our cost guide, browse all our services, or compare adjacent sizes — step down to 50 kW or step up to 100 kW. Common questions are covered on our FAQs page. For policy detail see Ofgem's market guidance on the SEG and connection process.