How much does a 100kW commercial solar system cost in 2026?
A 100kWp commercial solar installation is the most common SME-scale UK project — large enough to use scale efficiencies on bill-of-materials and labour, small enough that AIA headroom typically applies for the full project, and large enough that the FYA/special-rate-pool route also delivers materially. Most 100kWp projects sit in the £85k–£110k turnkey bracket in 2026.
£85,000–£110,000
£850–£1,100
95 MWh
3.5–4.5 years
Cost breakdown — where the money goes on a 100kW project
Hardware (modules, inverters, mounting)
£48k–£60k
Higher per-Wp than larger projects due to lower volume — typically £0.50–£0.65/Wp on hardware vs £0.45/Wp on 500kW+ projects.
Installation labour (M&E, roof access)
£14k–£20k
Heavily dependent on roof condition. New industrial units run lower; aged roofs requiring scaffold can push to upper end.
Soft costs (DNO, structural, design)
£8k–£14k
DNO charges typically modest at 100kWp (under G99 threshold for connection studies). Structural surveys £3k–£8k.
Commissioning & certification
£3k–£5k
G98 commissioning for sub-100kWp; G99 for above. MCS certification £2k–£3k where SEG export tariff is wanted.
Margin and contingency
£12k–£20k
Installer margin plus 5% project contingency. Smaller projects often carry higher margin percentage to absorb fixed overhead.
Worked example: 100kW commercial solar at central pricing
£95,000
£11,875 corp tax saved (50% FYA × 25%)
£20k (95MWh × ~21p blended self-consumption + export)
-£63k (after capex, FYA, savings)
12–17%
4.5–6 years
Run your own numbers in our interactive calculator →
Best fit
Profitable trading SMEs with stable daytime demand on a single site. Companies with AIA headroom available for the period (full 100% relief in year one — typically stronger than FYA route at this scale).
Best for
A 100kW system suits SME industrial unit, single-shift manufacturer, smaller distribution warehouse, professional services occupying a single mid-sized commercial unit.
Not suitable
Loss-making businesses without trading subsidiaries, very short remaining lease tenure (under 5 years), buildings with very poor roof condition where structural reinforcement materially shifts the bottom line.
Other system sizes
200kW system cost
£800–£1,000 per kWp
500kW system cost
£720–£900 per kWp
1MW system cost
£700–£900 per kWp
100kW cost FAQs
Is 100kW the right starting size for my SME?
Should I claim AIA or 50% FYA on a 100kW project?
Why does £/kWp go up at smaller sizes?
How long does a 100kW project take from order to commissioning?
What does a 100kWp commercial solar system cost in 2025?
A 100kWp commercial solar installation typically costs £80,000–£105,000 for the complete supply and install, including panels, inverters, cabling, mounting system, monitoring equipment, DNO notification, and commissioning. This price range reflects competitive market pricing from reputable installers — not budget-end quotes that may exclude key components or warranty provisions.
After claiming Annual Investment Allowance (AIA) at 25% Corporation Tax rate, the effective net cost falls to £60,000–£79,000. For most commercial buildings consuming 100,000+ kWh per year, payback is typically achieved in 5–7 years before accounting for energy price inflation.
What is included in a 100kWp installation
| Component | Specification | Typical cost range |
|---|---|---|
| Solar panels (330–430Wp modules) | 240–300 panels, tier-1 manufacturers (JA Solar, Jinko, LONGi, REC) | £25,000–32,000 |
| Inverters | 3–phase string inverters or hybrid inverters, 10yr+ warranty | £8,000–12,000 |
| Mounting system | Roof-type specific (ballasted flat, in-roof, on-roof pitched) | £10,000–15,000 |
| DC/AC cabling and electrical work | Cable runs, combiner boxes, AC isolation, consumer unit upgrades | £8,000–12,000 |
| Monitoring system | Online portal, generation meter, export meter | £2,000–3,500 |
| DNO application and G98/G99 | Distribution network operator notification and application | £500–1,500 |
| Scaffolding and access | Health and safety compliant access provision | £3,000–5,000 |
| Installation labour | 3–5 day install for 100kWp | £5,000–8,000 |
| Commissioning and documentation | MCS certificate, O&M manual, warranty documents | £1,500–2,500 |
Factors that affect 100kWp pricing
Roof type
Flat roofs with ballasted mounting systems are typically 8–12% cheaper than pitched roofs requiring penetrating rail systems. Ground-mount systems cost 5–10% more than flat-roof ballasted due to groundworks and civil engineering.
Location and access
London and South East installs cost 10–15% more due to higher labour rates. Remote rural locations may add 5–10% for travel and accommodation. Constrained access (multi-storey buildings, narrow streets) increases scaffolding costs.
Grid connection complexity
If your site has limited import capacity, the DNO may require infrastructure upgrades (transformer, reinforced cables) before approving a 100kWp system. Upgrade costs can range from £5,000 to £80,000+ and are usually the responsibility of the site owner.
Panel specification
Tier-1 panels from established manufacturers typically cost 10–15% more than lesser-known brands. For a long-term commercial installation, the premium is worthwhile — better degradation warranties (0.5% vs 0.8% per year) and bankability for future sale or refinancing.
100kWp economics: energy generation and financial returns
| Location | Annual generation | Annual electricity saving | Annual SEG income | Year 1 total benefit |
|---|---|---|---|---|
| South England (London/SE) | 90,000–95,000 kWh | £24,300–25,650 | £2,700–2,850 | £27,000–28,500 |
| Midlands (Birmingham/Leicester) | 84,000–89,000 kWh | £22,680–24,030 | £2,520–2,670 | £25,200–26,700 |
| North England (Manchester/Leeds) | 79,000–84,000 kWh | £21,330–22,680 | £2,370–2,520 | £23,700–25,200 |
| Scotland (Edinburgh/Glasgow) | 76,000–82,000 kWh | £20,520–22,140 | £2,280–2,460 | £22,800–24,600 |
| Wales (Cardiff/Swansea) | 82,000–88,000 kWh | £22,140–23,760 | £2,460–2,640 | £24,600–26,400 |
Generation figures assume 100% self-consumption of daytime generation; excess (off-peak or weekend) is exported at SEG rate. Electricity saving calculated at £0.27/kWh (typical SME blended rate 2025). SEG rate assumed at £0.03/kWh.
Payback and ROI for 100kWp
| Funding method | Net cost after tax | Annual benefit | Payback period | 20yr IRR |
|---|---|---|---|---|
| Cash purchase + AIA | £60,000–79,000 | £25,000–28,000 | 2.5–3.5 years | 28–34% |
| Green loan (7% APR, 7yr) | £0 upfront (AIA in yr1) | £25,000 saving less £14,000 repayment | Cash positive yr1 | 18–22% |
| Asset finance (HP, 5.5% APR) | 10–20% deposit (~£10,000) | £25,000 saving less £17,000 HP | Cash positive yr2 | 16–20% |
| PPA (£0.09/kWh) | £0 upfront | £18,000 (PPA discount only) | N/A (no investment) | N/A |
Who installs 100kWp commercial systems?
MCS-certified commercial installers
All commercial solar installations must be installed by MCS (Microgeneration Certification Scheme) certified contractors to qualify for SEG. Verify MCS certification before appointing any installer.
Getting multiple quotes
For a 100kWp system (£80,000–105,000), always obtain 3 quotes from independent installers. Price variation of 15–25% is common. Use a comparison site or specialist solar broker to run a competitive process efficiently.
Checking warranties
Minimum standards: panel product warranty 12 years+, panel power warranty 25–30 years (>=80% at 25yr), inverter warranty 10 years+, installation warranty 2 years workmanship. Insist on these as contract conditions.
Get a comparable 100kW cost benchmark for your specific site
Send postcode, roof area, and annual electricity consumption. We return an indicative capex range plus the after-tax model across all six finance structures, sized for 100kW.
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