30kW Commercial Solar Systems for UK Businesses

A 30 kW commercial solar system is one of the most-quoted sizes for UK SMEs in 2026. It fits the typical 180 sqm SME unit roof without redesign, sits well below the G98 grid-connection threshold so the DNO process runs fast, and lands in a price band where 100% Annual Investment Allowance turns a £31,500 capex into a sub-£24,000 net cost for a profitable limited company. The numbers below come from PVSyst yield modelling against half-hourly meter data — not generic kWh-per-kWp assumptions.

The 30 kW band is what we typically recommend for SME offices with 25-40 staff, mid-format retail units, small workshops with 1-2 CNC machines or compressors, GP surgeries, multi-chair dental practices, restaurants and small hotels with up to 30 rooms. It is the sweet spot where the install is large enough to make G99 worth avoiding, large enough that procurement justifies a proper survey-led design, and small enough that capex sits comfortably inside a single year's AIA headroom for almost any limited company.

What 30kW looks like physically

A 30 kW system in 2026 uses approximately 55 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 50. You need approximately 180 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 30 kW three-phase string inverter or 2 x 15 kW units (typically Solis, SolarEdge, Fronius or SMA) connected through MCS-compliant DC and AC switchgear, with sub-string monitoring resolution and full G98 connection paperwork lodged with your DNO. SPD (Surge Protection Device) coordination is standard across DC, AC and signal circuits to protect the inverter against lightning-induced transients.

Cost breakdown for a 30kW install in 2026

Turnkey 2026 pricing for a properly specified 30 kW system runs £27,000-£36,000 plus VAT, working out at roughly £900-£1,200 per kW. That price band includes 55 tier-1 panels at trade pricing, a commercial-grade three-phase string inverter, an MCS-spec mounting system (ballasted on flat roofs, rail-mounted on trapezoidal sheets or pitched tile roofs), all DC and AC cabling, surge protection, fire-safe DC isolators, an MCS-spec consumer unit, half-hour-resolution monitoring with a dedicated cloud portal, scaffolding, structural sign-off from a chartered engineer, electrical sign-off, full G98 connection paperwork, and 12 months of post-commissioning support.

Where a 30 kW project goes over budget is almost always one of three known knowns: an asbestos-cement roof needing licensed removal (£3,500-£12,000), a single-phase supply that must be upgraded to three-phase (£4,000-£8,500 for the DNO supply alteration), or roof reinforcement where the existing structure can't carry the array weight (£2,000-£8,000 depending on extent). We identify these at survey stage and quote them clearly. We do not bury them in vague site-prep entries that get inflated as change orders.

On AIA: 100% Annual Investment Allowance covers the full capex up to the £1m annual cap. A £31,500 install reduces a profitable limited company's corporation tax bill by £7,875 in year one (at the 25% main rate). That drops the effective net cost to around £23,600 before counting any energy savings. For sole traders and partnerships AIA still applies through self-assessment, with the relief netting against trading profits at marginal rates. The Land Remediation Tax Relief can recover an additional 50% of any asbestos-removal element through corporation tax, which is worth checking with your accountant if the roof needs work.

Generation and savings

A typical UK 30 kW system generates 27,000-28,000 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 single biggest driver of project economics. A 30 kW system on a multi-shift workshop or a 24/7 convenience store typically achieves 80-88% self-consumption. On a 9-5 office that closes at weekends, self-consumption falls to 65-75%. The difference between 70% and 85% self-consumption on a 30 kW system is roughly £1,300 of additional annual benefit — material to the IRR calculation.

At 75% self-consumption with a 24p/kWh blended import price, a 30 kW system avoids around £4,950 of grid energy purchases per year. The remaining 6,800 kWh exports to grid at the SEG rate, which in 2026 typically sits between 4p/kWh and 15p/kWh depending on tariff. At a blended 6p/kWh SEG rate that adds £408 of export income, taking total year-one benefit to around £5,500-£7,000. Simple payback on £31,500 capex (or £23,600 net of AIA) lands at 6-7 years. 25-year IRR is 13-16% and 25-year NPV at a 7% discount rate is approximately £105k-£135k.

DNO grid connection — G98 keeps things fast

Sub-50 kW per phase on a three-phase supply qualifies for G98 fast-track notification: we file the application, the DNO has 11 working days to respond with technical conditions, and unless your site sits on a constrained portion of the network the answer is usually a standard offer with no reinforcement charge. Total G98 turnaround typically runs 4-8 weeks. At 30 kW you sit comfortably inside G98 territory on any standard three-phase supply. If your supply is single-phase only, the 30 kW size will trigger a supply upgrade to three-phase (typically £4,000-£8,500 paid to the DNO) — at that point we sometimes recommend dropping the system to 17 kW per phase to stay within single-phase G98, depending on your trading profile and load curve. Compare that with G99 (above 50 kW per phase) where DNO response timescales now run 6-18 months and reinforcement charges can range from £5,000 to £100,000+. Avoiding G99 at the 30 kW band is a meaningful saving.

Best-fit sectors for the 30kW band

From our 2025 install book, the 30 kW band overweighted across six sub-verticals. SME offices with 25-40 staff in light-industrial estate units (decent daytime load, predictable hours, good roof access). Mid-format independent retail and convenience stores (chiller load drives high self-consumption). Small workshops running CNC, sheet-metal or extraction equipment in single-shift operation. GP surgeries and multi-chair dental practices where diagnostic imaging, sterilisation and HVAC drive consistent daytime load. Independent restaurants, gastropubs and small-format quick-service food where kitchen extraction, refrigeration and lighting run continuously. Small hotels and B&Bs with up to 30 rooms where laundry, kitchen and HVAC drive year-round demand. These overlap closely with our sectors coverage.

Worked example: a Buckinghamshire SME marketing agency, 32 staff, 5-day working pattern, three-phase 200 A supply, 195 sqm pitched tile roof south-facing, 56,000 kWh annual consumption. Quoted £30,800 plus VAT for 30.3 kW (55 x 550 Wp Trina Vertex panels, Solis-S6 30 kW inverter, K2 rail-mount). Modelled year-one yield 27,500 kWh. Self-consumption modelled at 73%, so 20,100 kWh avoid the grid at 25p/kWh blended (£5,025 saved) and 7,400 kWh export at 6p/kWh SEG (£444). Total year-one benefit £5,469. AIA tax relief £7,700. Simple payback 5.6 years, 25-year IRR 16.8%.

Financing a 30kW system

Three financing routes work at 30 kW scale. Cash plus AIA delivers the strongest IRR for any limited company with corporation tax exposure — the £7,875 year-one tax relief shortens payback by around 18 months versus a finance route. Asset finance over 5-7 years (around £530-£640 per month over six years on £31k capex) is the route most of our 30 kW SME customers actually choose: monthly finance payment is typically lower than 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 — always confirm the structure before signing. PPA structures are not commercially viable below 100 kW. We model both viable routes side-by-side 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 30 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 25 kW or step up to the SME mainstay 50 kW. Common questions are covered on our FAQs page. For policy detail see Ofgem's market guidance on the SEG and connection process.