100kW Commercial Solar Cost
100kW Commercial Solar System Cost & Payback UK 2026
A 100kW commercial solar system fits mid-sized warehouses and similar properties with approximately 560 m² of usable roof. Annual savings around £28,500, payback in 3.2–4.2 years.
100kW
System size
~95k
Annual kWh
£28k
Annual saving
3.2yr
Payback (low)
A 100kW commercial solar system is one of the most common UK rooftop sizes — sized for mid-sized warehouses, secondary schools, mid-tier hotels, mid-sized factories, distribution depots, larger offices, supermarkets. This page gives you the live 2026 cost, generation, savings, and payback numbers, taken directly from our installed fleet. No marketing fluff: real numbers from real installs.
100kW Solar System — Quick Numbers (UK 2026)
Here is what a 100kW commercial solar PV system typically delivers across the UK in 2026:
- Typical panel count: ~220 panels at 455 Wp tier-1 monocrystalline.
- Roof area required: approximately 560 m² of usable, south-facing or east/west roof.
- Annual generation: ~95,000 kWh per year (UK national average — Midlands).
- Installed cost: £90,000–£115,000 including VAT, design, supply, install, DNO, commissioning.
- First-year saving: £27,500–£28,500 (assumes 80% self-consumption, 20% export at SEG rates).
- Simple payback: 3.2–4.2 years before any AIA or finance is applied.
- 25-year lifetime savings: £712,000+ at current grid prices.
100kW Solar System Cost Breakdown
The £90,000–£115,000 install range for a 100kW system breaks down approximately as:
- Panels (45%): tier-1 monocrystalline panels (JA Solar, Trina, Longi, Jinko) — £40,500–£51,750
- Inverters (15%): string or central inverters (SolarEdge, SMA, Huawei) — £13,500–£17,250
- Mounting & cabling (12%): roof-rated mounting hardware, DC cable, AC cable — £10,800–£13,800
- Installation labour (15%): rigging, electrical, MCS commissioning — £13,500–£17,250
- Design, DNO & paperwork (8%): structural sign-off, G99 application, MCS pack — £7,200–£9,200
- Contingency (5%): scaffolding, weather, late-stage variations — £4,500–£5,750
100kW Solar System Payback Analysis
A 100kW system installed in 2026 pays back in approximately 3.2–4.2 years for most UK businesses. The exact figure depends on three factors:
- Self-consumption ratio. Higher daytime electricity use = faster payback. A 100kW system feeding a 24/7 industrial load pays back ~6–8 months faster than one feeding a 9-to-5 office.
- Grid tariff. Businesses paying 30p+/kWh see paybacks at the lower end (3.2 years); businesses on legacy contracts at 18–22p/kWh see paybacks at the upper end.
- Finance route. Capital purchase has the fastest paper payback. PPA gives day-one cashflow positive without capital outlay. Asset finance over 7 years often gives a net-positive monthly position from month one.
What Properties Suit a 100kW System?
A 100kW commercial solar system is a strong fit for mid-sized warehouses, secondary schools, mid-tier hotels, mid-sized factories, distribution depots, larger offices, supermarkets. The roof must offer approximately 560 m² of usable space — clear of significant shading, plant rooms, skylights, and rooflights. Roof age matters: panels carry 25-year warranties and are typically not lifted off mid-life, so the underlying roof should have ≥10 years of remaining life. Where the roof is older, our team specs a coordinated roof-and-solar refurbishment.
Tax Treatment of a 100kW Solar Investment
For UK companies, a 100kW solar system qualifies for either:
- Annual Investment Allowance (AIA): 100% first-year capital allowance up to the AIA cap (£1m as at 2026). For most 100kW systems, 100% of the install cost can be written off against the company's taxable profit in year one.
- Full Expensing: 100% deduction on main-pool plant for limited companies. Full Expensing is now permanent for solar PV under HMRC's 2024–2026 capital allowances reform.
For a £90,000–£115,000 install at 25% corporation tax, the post-tax effective cost reduces to £67,500–£86,250. Always confirm allowances with your accountant before committing.
Get a Fixed-Price 100kW Solar Quote
Send us your last 12 months of half-hourly meter data plus a sketch (or postcode) of the building. We will return:
- A specific 100kW system design tailored to your roof — panel count, layout, orientation, inverter sizing.
- An accurate annual generation forecast modelled in PVSyst from your local irradiance data.
- A first-year and 25-year saving forecast based on your actual tariff structure (not generic averages).
- A fixed-price quote inclusive of design, supply, install, DNO, commissioning, MCS handover.
The desk feasibility takes 3–5 working days and is free. From signed proposal to commissioned system: typically 8–14 weeks.
Frequently Asked Questions
What is a 100kW solar system?
A 100kW (kilowatt) commercial solar PV system uses approximately 220 solar panels with a combined nameplate capacity of 100 kilowatts. It generates around 95,000 kWh of electricity per year in the UK, enough to offset 60–90% of typical commercial electricity usage.
How much does a 100kW solar system cost in the UK?
As of 2026, a 100kW commercial solar system costs £90,000–£115,000 fully installed in the UK. This includes panels, inverters, mounting, cabling, electrical work, design, DNO application, MCS commissioning, and 25-year output warranty.
How much will a 100kW solar system save me?
A 100kW system typically saves £27,500–£28,500 per year, depending on grid tariff, self-consumption, and export rates. Over the system's 25-year warrantied life, lifetime savings are typically £627,000+ even after accounting for panel degradation.
How long does a 100kW solar install take?
From signed contract to commissioning: typically 8–14 weeks for a 100kW rooftop system. This includes 1–2 weeks design and DNO submission, 4–8 weeks lead time for panels and inverters, 1–3 weeks of on-site install, and final MCS commissioning.
What roof size do I need for a 100kW system?
A 100kW solar system requires approximately 560 m² of usable roof. The roof should be south, east, or west facing, with no major shading from neighbouring buildings or trees. Flat roofs work well using ballasted mounting at 10–15° tilt; pitched roofs use rail-mounted in-line systems.
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100kW Solar: Who It's Right For
A 100kW commercial solar system is the most commonly installed size for UK SMEs. It suits businesses with annual electricity consumption of 100,000-160,000 kWh — equivalent to a bill of approximately £25,000-£45,000 at current commercial rates. Typical candidates include: warehouses of 10,000-25,000 sq ft, offices of 15,000-30,000 sq ft (with full AC), medium-sized retail units with HVAC and refrigeration, and manufacturing units with moderate CNC or process equipment.
100kW is also the size class that sits most comfortably within standard DNO G99 connections. For most sites with an existing three-phase 200A or larger supply, a 100kW solar system can connect without DNO reinforcement — the existing supply capacity is sufficient to handle both export and the site's normal demand simultaneously. This eliminates the £10,000-£50,000 reinforcement costs that can affect larger systems on constrained substations.
100kW Solar: Who It's Right For
A 100kW commercial solar system is the most commonly installed size for UK SMEs. It suits businesses with annual electricity consumption of 100,000-160,000 kWh — equivalent to a bill of approximately £25,000-£45,000 at current commercial rates. Typical candidates include: warehouses of 10,000-25,000 sq ft, offices of 15,000-30,000 sq ft with full AC, medium-sized retail units with HVAC and refrigeration, and manufacturing units with moderate CNC or process equipment.
100kW is also the size class that sits most comfortably within standard DNO G99 connections. For most sites with an existing three-phase 200A or larger supply, a 100kW solar system can connect without DNO reinforcement — the existing supply capacity is sufficient to handle both export and the site's normal demand simultaneously. This eliminates the £10,000-£50,000 reinforcement costs that can affect larger systems on constrained substations.