How to Choose a Solar Installer in 2026 UK: 10-Point Vetting Checklist
Solar PV is one of the largest single home purchases UK homeowners make in 2026 — and the industry has more cowboys per square mile than any sector outside paving. Picking the wrong installer can cost £6,000–£12,000 if the panels underperform, the wiring fails Part P, or the company disappears with your deposit. This is the 10-point checklist for choosing a UK solar installer in 2026 that's MCS-certified, RECC-protected, and actually owns the work rather than sub-contracting.
Why Installer Choice Matters More Than Panel Choice
Two installers fitting the same JinkoSolar or Longi panels deliver outputs that vary by 10–25% in real-world performance. Roof angle alignment, micro-shading analysis, inverter sizing, MPPT design, DC string layout — these are installer decisions, not panel-brand decisions. Panels have a 25-year linear warranty that's nearly identical across all Tier 1 brands. The installer is what changes from year 1 to year 25. Get the installer right; the panels are interchangeable.
Vet Every Solar Installer Against These 10 Points
Walk through each point before signing. Missing any one of the first six is a deal-breaker. The remaining four are quality signals — installers who tick all 10 are the top 15% of the UK industry.
✅ 1. MCS certified (verify the number)
Microgeneration Certification Scheme membership. Verify the MCS number against the database at mcscertified.com — the most common scam is quoting a real MCS number that belongs to a different company.
✅ 2. RECC consumer code member
Renewable Energy Consumer Code. Required for MCS membership but worth checking separately at recc.org.uk — gives you deposit protection (up to £30,000) and complaints process.
✅ 3. NICEIC or NAPIT Part P registered
Solar PV involves notifiable electrical work. The installer (or their employed electrician) needs Part P certification. Without it, your building control sign-off won't go through and SEG registration will fail.
✅ 4. Public liability insurance £2m+
Working at height on your roof requires £2m minimum cover. Ask to see the certificate dated within the last 12 months. Don't accept "we have insurance" without paper proof.
✅ 5. Direct employees, not subcontractors
Ask explicitly: "will your own employees do the install, or sub-contractors?" Subbed installs are still legal but quality control drops sharply. National "lead aggregators" almost always sub-contract.
✅ 6. Performance guarantee in kWh/year
Quote should include estimated annual generation in kWh and a guarantee that performance won't fall below 90% of that in years 1–3. Without it, you have no recourse if the system underperforms.
✅ 7. Workmanship warranty 10+ years
Separate from panel warranty (25 years from manufacturer). Covers installation defects: roof penetrations, cable routing, mounting brackets. 5-year minimum, 10-year mark of a quality installer.
✅ 8. Deposit ≤25% of project value
RECC limit. Anything more is a red flag. Reputable installers ask for 10–20% at signing, 40–50% at panel delivery, balance on commissioning. Demands of 50%+ upfront usually signal cashflow problems.
✅ 9. Companies House > 3 years trading
Check the company at companieshouse.gov.uk. A 3-month-old "Ltd" company offering 10-year warranties is meaningless. Reputable installers have track record; scam companies have new registrations every 6–12 months.
✅ 10. Site survey before final quote
Any installer who quotes from satellite imagery alone is missing 30% of the picture. A site survey checks roof condition, rafter spacing, loft access for cabling, fuse-board capacity, and consumer-unit headroom. Refuse to sign without one.
6 Patterns That Mean Walk Away
UK solar cold-call complaints to Trading Standards doubled between 2023 and 2026. The patterns below are consistent across most reported scams — encounter any of them and the installer should be off your shortlist immediately.
🚩 Cold call or door-knock
Reputable solar installers don't cold-call. The MCS code of practice actively discourages it. If they reached you without you reaching out first, treat with extreme caution.
🚩 "Today-only" pricing
Time pressure is the classic scam signature. A real £12,000 system isn't going to be £4,000 cheaper if you decide tonight. Genuine MCS installers honour their quotes for 28+ days.
🚩 No MCS number on quote
MCS certificate number must be on the written quote. Verbal claims of MCS membership without the number are a deal-breaker — almost always indicate sub-contracting or fraud.
🚩 Deposit demand > 25%
RECC limits deposits to 25% of contract value. Anything more is a violation of the code and a strong signal the company is using customer deposits as working capital.
🚩 Sub-contracted via "associate" company
"We use our partner installers" or "our trusted associates" means a different company will actually do the work. Your contract is with one company; the work is done by another. If anything goes wrong, both will point at the other.
🚩 No site survey before quote
Quoting from Google Maps / satellite imagery without seeing the roof is industry malpractice. Real costs only emerge from a site visit — anything quoted blind will either come in over budget mid-install or skip essentials.
8 Questions to Ask Before Signing
Print or save these. Ask every shortlisted installer the same eight questions and compare written answers — the patterns of who hedges, who's specific, and who admits "depends" will tell you who actually knows their craft.
- Who specifically will install? Direct employees or subcontractors? Get names if subcontracted.
- What's the estimated annual generation in kWh for my roof? Compared to the regional average for my orientation and pitch.
- What's your workmanship warranty length and what does it cover? Get it in writing — verbal warranties are worthless.
- What happens if the system underperforms? Specific remedy: refund? Make-good? Additional panels? Don't accept "we'll look into it".
- Who handles the SEG (Smart Export Guarantee) application? A good installer manages the paperwork; a bad one leaves it to you.
- Is scaffolding included in the quote? Often a £400–£1,200 hidden cost added later.
- What inverter brand, and why? SolarEdge, Enphase, GoodWe, Fronius are the major brands. Their answer should be technical — power optimisation, system monitoring features, warranty terms.
- Can I have three previous customer references in my postcode area? Phone numbers, not just glowing testimonials. The willingness to provide them is a quality signal.
National vs Local Installers: Which is Right for You?
The UK solar industry split into two tiers around 2022: a handful of national brands (Octopus Energy Services, EDF Solar, British Gas Solar, Eon Next) and several thousand local MCS firms. Both are legitimate — the choice depends on your priorities.
National installers
Pros: Backed by a utility with deep pockets, system monitoring apps, 25-year warranty backed by parent company, won't go bust.
Cons: 15–25% more expensive, slower scheduling, sub-contracted install (usually), less flexibility on spec.
Local MCS firms
Pros: Direct employees, faster scheduling, more spec flexibility, owner is on site, 15–25% cheaper for same equipment.
Cons: Business risk if they go bust, warranty depends on company solvency, more variance in install quality.
The smart move is a mixed quote ladder: get two local quotes and one national quote. The local ones tell you the market floor; the national one tells you the premium for guaranteed backing. Most homeowners find good local installers deliver 90% of the national service at 75% of the cost.