100kW Commercial Solar: Real UK Case Studies (Warehouse, Care Home, Food Production)

A 100kW commercial solar system in the UK typically generates 90,000–95,000 kWh a year, costs £70,000–£110,000 to install (£700–£1,100 per kW ex VAT), and pays back in roughly 3–4.5 years depending on how much of the electricity you use on site. The single biggest variable is self-consumption: a warehouse running one daytime shift keeps around 75% of its generation, while a 24/7 care home or a refrigeration-heavy food producer keeps 90%+ — and the higher your self-consumption, the faster the return. Below are four representative UK case studies showing exactly how those numbers play out across different building types.

These are anonymised, sector-and-region-typical projects rather than named clients — but every figure is modelled from published 2026 UK pricing and yield data for that kind of site. For the underlying pricing model, see our 100kW solar system cost breakdown; for more worked examples across sectors, see our full library of commercial solar case studies.

What does a 100kW solar system actually produce?

At UK yields of 900–1,150 kWh per kWp per year, a 100kW array delivers about 90,000–95,000 kWh annually — enough to cover a meaningful chunk of most SME and mid-market commercial loads. In physical terms that is roughly 220–250 panels (400–460W each) needing 500–650 m² of unshaded south, east or west-facing roof. On a modern flat industrial roof it is a clean, fast install; on multiple pitched roof planes (common on care homes and older buildings) the per-kW cost drifts to the upper end of the band.

The economics hinge on self-consumption — the share of generation you use directly instead of exporting. Every kWh you self-consume displaces grid electricity at 25–28p; every kWh you export earns just 7–8p under the Smart Export Guarantee. That 3-to-4x gap is why the same 100kW system saves very different amounts at different sites.

Case study 1 — Yorkshire distribution warehouse (75% self-consumption)

A logistics and distribution operator in West Yorkshire fitted a 100kW rooftop array across a single large flat industrial roof. The building runs a standard Monday–Friday daytime operation: forklift charging, LED high-bay lighting, conveyor and packing lines, and office HVAC.

• Capex: £82,000 ex VAT (≈£820/kW)
• Annual generation: ~92,000 kWh
• Self-consumption: 75% (daytime picking and packing load)
• Self-consumed: 69,000 kWh × 26p = £17,940
• Exported: 23,000 kWh × 7.5p = £1,725
• Year 1 saving: ~£19,665
• AIA relief: 100% first-year allowance on £82,000 = ~£20,500 corporation-tax saving, cutting effective net cost to ~£61,500
• Payback: ~4.2 years gross, ~3.1 years post-AIA
• CO2 saved: ~19 tonnes/year

The warehouse is the archetypal “good but not perfect” solar site: huge cheap roof, but a single shift means a quarter of summer generation spills to export. Adding commercial battery storage cost modelling to soak up evening and weekend surplus would lift self-consumption toward 85% and shave several months off payback.

Case study 2 — North West care home (24/7 baseload, 90% self-consumption)

A residential care home in the North West installed 100kW across several pitched and flat roof sections. Unlike the warehouse, a care home never switches off — heating and hot water, commercial laundry, kitchens, nurse-call and medical equipment, lighting and refrigeration all run around the clock. That continuous baseload is close to the ideal solar demand profile.

• Capex: £88,000 ex VAT (≈£880/kW — multiple roof planes raise the install cost)
• Annual generation: ~90,000 kWh
• Self-consumption: 90% (genuine 24/7 baseload)
• Self-consumed: 81,000 kWh × 27p = £21,870
• Exported: 9,000 kWh × 7p = £630
• Year 1 saving: ~£22,500
• AIA relief: 100% allowance on £88,000 = ~£22,000 tax saving, net cost ~£66,000
• Payback: ~3.9 years gross, ~2.9 years post-AIA
• CO2 saved: ~18.6 tonnes/year

Even though the care home paid more per kW than the warehouse, it saves more per year because it self-consumes almost everything it generates. This is the core lesson of commercial solar: a match between generation and demand matters more than roof cost.

Case study 3 — Yorkshire food producer (refrigeration, 92% self-consumption)

A food-production business in Yorkshire — chilling, cold storage and processing — fitted 100kW on its main production roof. Continuous refrigeration is a near-flat baseload that runs day and night, seven days a week, giving the highest self-consumption of all four sites.

• Capex: £84,000 ex VAT (≈£840/kW)
• Annual generation: ~94,000 kWh
• Self-consumption: 92% (continuous refrigeration and chilling load)
• Self-consumed: 86,480 kWh × 25p = £21,620
• Exported: 7,520 kWh × 7p = £526
• Year 1 saving: ~£22,150
• AIA relief: 100% allowance on £84,000 = ~£21,000 tax saving, net cost ~£63,000
• Payback: ~3.8 years gross, ~2.8 years post-AIA
• CO2 saved: ~19.5 tonnes/year

As an energy-intensive manufacturer, this producer may also qualify for Industrial Energy Transformation Fund support on top of solar, and its heavy-user electricity contract (25p rather than 27–28p) is offset by exceptional self-consumption. Food and cold-chain sites are among the strongest commercial solar cases in the UK.

Case study 4 — Midlands light-industrial unit (single-shift engineering)

A precision-engineering and fabrication business in the Midlands took 100kW on a large, sound, flat industrial roof — the cheapest install of the four. The trade-off is a single daytime shift with intermittent machinery load, so self-consumption is the lowest here.

• Capex: £79,000 ex VAT (≈£790/kW — ideal large flat roof)
• Annual generation: ~91,000 kWh
• Self-consumption: 68% (single-shift, intermittent CNC and compressor load)
• Self-consumed: 61,880 kWh × 26p = £16,090
• Exported: 29,120 kWh × 7.5p = £2,184
• Year 1 saving: ~£18,270
• AIA relief: 100% allowance on £79,000 = ~£19,750 tax saving, net cost ~£59,250
• Payback: ~4.3 years gross, ~3.2 years post-AIA
• CO2 saved: ~18.8 tonnes/year

This site is the clearest battery candidate of the four. A 60–90 kWh battery capturing the ~29,000 kWh currently exported could push self-consumption toward 85%, adding roughly £3,000–£4,000 a year in avoided import — worth modelling against the battery capex of £400–£700 per kWh.

How do the four 100kW case studies compare?

Site	Capex (ex VAT)	Generation	Self-consumption	Year 1 saving	Net cost post-AIA	Payback (post-AIA)	CO2/yr
Yorkshire warehouse	£82,000	92,000 kWh	75%	~£19,665	~£61,500	~3.1 yrs	~19 t
North West care home	£88,000	90,000 kWh	90%	~£22,500	~£66,000	~2.9 yrs	~18.6 t
Yorkshire food producer	£84,000	94,000 kWh	92%	~£22,150	~£63,000	~2.8 yrs	~19.5 t
Midlands light-industrial	£79,000	91,000 kWh	68%	~£18,270	~£59,250	~3.2 yrs	~18.8 t

Read the table by column, not by row. Capex barely moves (£79k–£88k, a 12% spread), but the annual saving swings by nearly £4,300 — driven almost entirely by self-consumption. The care home and food producer, both continuous-load sites, deliver sub-3-year post-AIA payback; the single-shift warehouse and industrial unit sit at 3.1–3.2 years and are the sites where a battery earns its keep.

How AIA turns a 4-year payback into a 3-year one

Every one of these projects uses the Annual Investment Allowance (AIA) — a 100% first-year capital allowance that lets a profitable, corporation-tax-paying business deduct the entire qualifying cost of the solar system from taxable profits in the year of purchase. At the 25% main rate of corporation tax, that means roughly a quarter of the headline cost comes straight back as reduced tax, cutting the effective net cost to about 75% of the sticker price.

For a £84,000 system that is ~£21,000 back — the difference between a 3.8-year and a 2.8-year payback. AIA is why nearly every commercially-financed 100kW project in the UK is modelled on a net, post-tax basis rather than the gross headline number. It applies to the equipment cost regardless of sector, so it benefits the warehouse, the care home, the food producer and the engineering unit equally.

Which building types make the best 100kW candidates?

The pattern across all four case studies is consistent — the more continuously you run, the better 100kW solar performs:

• Best: 24/7 operations — care homes, food production and cold storage, data-adjacent facilities, hotels. Self-consumption 88–95%, payback under 3 years post-AIA.
• Strong: multi-shift or extended-hours sites — busy warehouses, manufacturing with two shifts, leisure. Self-consumption 75–85%.
• Good with a battery: single-shift daytime operations — light-industrial units, offices, standard 9-to-5 warehouses. Self-consumption 60–75%, improved to ~85% by adding storage.

If your site sits in the third group, don’t discount solar — model it with storage. The full commercial battery storage cost picture often turns a 4.3-year payback into something closer to the continuous-load sites. And if you want to see the sizing and pricing logic behind a 100kW array in detail, our 100kW solar systems service page walks through panel counts, roof area, inverter set-up and the DNO process.

FAQ

How much does a 100kW commercial solar system cost in the UK? £70,000–£110,000 ex VAT, or roughly £700–£1,100 per kW. Large flat industrial roofs sit at the lower end (£790/kW); multiple pitched roof planes push toward the upper end (£880/kW). After AIA the effective net cost for a profitable business is around 75% of that.

How much electricity does 100kW generate per year? About 90,000–95,000 kWh in the UK, based on yields of 900–1,150 kWh per kWp per year depending on region, roof orientation and shading.

What is a realistic payback on 100kW solar? Roughly 3–4.5 years post-AIA. Continuous-load sites (care homes, food producers) hit under 3 years; single-shift sites land at 3–3.5 years, or better with a battery.

Why do two identical 100kW systems save different amounts? Self-consumption. Self-consumed electricity is worth 25–28p/kWh; exported electricity earns only 7–8p under the SEG. A site that uses 90% of its generation saves far more than one exporting 30%, even with the same hardware.

How much CO2 does 100kW of solar save? Around 18–20 tonnes of CO2 a year, based on ~90,000 kWh of generation displacing grid electricity at current UK carbon factors.

See what 100kW would do on your roof

The four case studies above are typical, not guaranteed — the right answer for your building depends on your roof, your load profile and your electricity contract. We model every 100kW enquiry against your real half-hourly consumption rather than a bill estimate, so the payback figure you get is yours, not an average.

Get a tailored 100kW commercial solar quote and we will return a sized system, capex, post-AIA net cost and a payback figure built on your actual demand. For further reading: our 100kW solar system cost guide, the wider commercial solar case studies library, and the 100kW solar systems service page.