Commercial Solar Myths: 12 Claims Checked Against the Data
Updated 10 November 2026 · SEO Dons Editorial
How were the twelve claims checked?
Each answer rests on a page read on 22 October 2026 from PVGIS, GOV.UK, legislation.gov.uk, MCS, the Energy Saving Trust, the National Federation of Roofing Contractors (NFRC) or a manufacturer's datasheet. Yield figures are PVGIS runs for 1 kWp with a 14% system loss. Some Energy Saving Trust pages are written for homes. No prices are quoted.
The twelve claims at a glance
| Claim | Verdict | Read more |
|---|---|---|
| 1. Solar does not work in UK weather | Wrong | Output by month |
| 2. Panels must face south | Mostly wrong | Panel output |
| 3. Panels wear out in 10 to 15 years | Wrong | Lifespan |
| 4. Panels damage roofs | Partly true | Roof mounting |
| 5. You must cover the whole roof | Wrong | Sizing |
| 6. Rooftop solar is a serious fire risk | Mostly wrong | RC62 and fire |
| 7. Planning permission is always needed | Mostly wrong in England | Planning |
| 8. MCS is required above 50 kW | Wrong | MCS |
| 9. Solar runs the site in a power cut | Wrong | Power cuts |
| 10. Batteries always pay | Wrong | Batteries |
| 11. Payback is always under five years | Wrong | Payback |
| 12. Commercial solar is zero-rated for VAT | Wrong | VAT |
Is solar output in the UK poor or short-lived?
Claim 1: Solar does not work in UK weather
PVGIS puts a south-facing array tilted at 35 degrees at about 853 kWh per kWp a year in Glasgow and about 1,122 in Plymouth. December gives about 2% of the year's output in Glasgow and about 4% in London, and the Energy Saving Trust notes that cells "can even work on cloudy days".
Verdict: wrong. Output is lower in winter, not absent. See UK solar output by month.
Claim 2: Panels must face south
The Energy Saving Trust says an east- or west-facing system "tends to get around 15-20% less energy than one facing directly south". PVGIS agrees for flat-roof style rows at 10 degrees: an east-facing array makes about 930 kWh per kWp in Plymouth against 1,122 facing south at 35 degrees, and about 845 against 1,019 in London, roughly 17% less.
Verdict: mostly wrong. Less per kWp is not a failed roof. See commercial panel output.
Claim 3: Panels wear out in 10 to 15 years
The Energy Saving Trust says panels "should last 25 years or more" and an inverter needs replacing "after around 12 years". LONGi's datasheet page for one module range lists a 30-year performance warranty and 0.35% power degradation a year from year 2, after 1% in the first year.
Verdict: wrong for the panels. The inverter is the shorter-lived part. See panel lifespan and degradation.
What do the roof and the planning system require?
Claim 4: Solar panels damage roofs
The Energy Saving Trust says no, "not if the solar panels are installed correctly". The NFRC adds that solar "directly alters the existing roof system": fixings penetrate the covering, panels add weight and drainage changes, so failure is more likely on a roof near the end of its life. It asks for a roof condition assessment before installation.
Verdict: partly true. The risk is an unassessed or worn roof, not panels as such. See flat roof mounting and fixing to metal roofs.
Claim 5: You must cover the whole roof
In England the permitted development right for non-domestic roofs excludes equipment "within 1 metre of the external edge of that roof", so edge-to-edge cover is outside it. The Energy Saving Trust lists "how much of the solar electricity you're able to use yourself" first among the factors that decide savings.
Verdict: wrong. Size to use; roof area is only the ceiling. See sizing a system and the 50 kW system.
Claim 6: Rooftop solar is a serious fire risk
A three-year BRE study for government found that "the incidence of such fires is very low" and still recommended better installation practice. MCS lists RC62 as "best practice guidance for reducing fire risks in commercial solar PV systems".
Verdict: mostly wrong. Rare is not nil, so design and workmanship matter. Read RC62 and fire safety. The latest fire service counts, and what they cannot show, are in the guide to solar panel fires on commercial roofs.
Claim 7: Planning permission is always needed
In England, Class J of the General Permitted Development Order covers "microgeneration solar PV equipment on a building" and "other solar PV equipment on the roof of a building", other than homes and blocks of flats. Microgeneration means up to 50 kW, and larger roof systems must first ask the council whether prior approval is needed. Listed buildings and their curtilage are excluded.
Verdict: mostly wrong in England. This is the England order, so check Wales, Scotland and Northern Ireland separately. See planning permission and conservation areas.
What do the rules and the equipment actually do?
Claim 8: MCS certification is required above 50 kW
MCS says its certification covers commercial and domestic installations "up to a certain size – 50kW for electrical technologies", so no MCS certificate exists to require above that. The HSE says a commercial client must appoint contractors and designers with "the skills, knowledge, experience and organisational capability".
Verdict: wrong. No MCS route above 50 kW does not mean no checks. See MCS and commercial solar and vetting an installer.
Claim 9: Solar keeps the site running in a power cut
The Energy Saving Trust says "Typically solar panels can't power your home during a power cut". The Energy Networks Association's fast-track conditions for small-scale G99 generation say the units "will not operate when there is a loss of mains situation", and the IET says island mode usually needs a switching arrangement.
Verdict: wrong. Backup is a separate design. See solar in a power cut.
Claim 10: Batteries always pay
The Energy Saving Trust, writing for homes, says battery savings "won't always be enough on their own to justify the cost of the battery". A battery works by "changing when you need electricity", and winter leaves little to move: PVGIS gives December about 2% of a year's output in Glasgow.
Verdict: wrong. It depends on the load shape and tariffs. See battery storage and AC and DC coupling.
Do the payback and tax claims hold up?
Claim 11: Payback is always under five years
A GOV.UK release of 3 June 2025 on the first 11 Great British Energy school installations lists a simple payback for each, from 4 years to 12 years. They are schools, not commercial buildings, but the spread is wide inside one programme.
Verdict: wrong. Payback comes from a site's cost, use and prices. See payback, ROI and IRR, payback by region and published project examples.
Claim 12: Commercial solar is zero-rated for VAT
HMRC's Notice 708/6 covers installations from 1 May 2023 to 31 March 2027 and says the 0% relief "applies to the services of installing energy-saving materials in residential accommodation and charitable buildings", and the standard VAT rate is 20%. A VAT-registered business can normally reclaim VAT on its purchases as input tax, which is different from not being charged it.
Verdict: wrong. The zero rate is for homes and charity buildings. See VAT on commercial solar.
What should a buyer do with these checks?
Ask any seller for the source behind a claim like these. Is commercial solar worth it? covers the wider question, and a reader who wants the checks applied to a specific building can send an enquiry through the form on the commercial PV systems page.
Sources
- European Commission Joint Research Centre, checked 22 October 2026: PVGIS; PVGIS 5.3 runs for 1 kWp with 14% loss at Glasgow, London and Plymouth (south, 35 degrees) and London and Plymouth (east, 10 degrees).
- Energy Saving Trust, checked 22 October 2026: Solar power facts; Solar panels: costs, savings and benefits explained; Battery storage.
- National Federation of Roofing Contractors, checked 22 October 2026: When solar PV is installed on end-of-life roofs.
- legislation.gov.uk, checked 22 October 2026: General Permitted Development (England) Order 2015, Schedule 2 Part 14; Energy Act 2004, section 82.
- GOV.UK, checked 22 October 2026: Fire incidents involving solar panels; First schools install Great British Energy solar panels; VAT Notice 708/6; VAT rates; VAT Notice 700.
- MCS, checked 22 October 2026: What is MCS certification?; RC62 library entry.
- Health and Safety Executive, checked 22 October 2026: Commercial clients.
- Energy Networks Association, checked 22 October 2026: Connecting generation to the electricity networks.
- Institution of Engineering and Technology, checked 22 October 2026: Battery storage webinar questions and answers.
- LONGi, checked 22 October 2026: LR8-66HVD 640-670M datasheet page.
Common questions
What is the biggest problem with solar panels for a business?
In the sources read for this page the weak points are the roof and the inverter, not the panels. The NFRC reports systems being fitted to roofs without an adequate assessment, and the Energy Saving Trust says an inverter needs replacing after around 12 years.
Why are people getting rid of solar panels?
The sources read for this page give no count of removals, so no figure is given. The NFRC lists costly removal and reinstatement of panels among the consequences when a roof fails prematurely, so roof work is one documented reason panels come off.
How can I check a yield claim in a quote?
Run the roof's location, tilt and direction through PVGIS, which the European Commission Joint Research Centre describes as answering how much electricity photovoltaics could produce and how production changes over the year. Compare its kWh per kWp with the quote and ask the seller to explain any gap.
Does a 30-year performance warranty mean panels last 30 years?
No. A warranty is a maker's conditional promise, not a forecast of life. LONGi's datasheet page pairs a 30-year performance warranty with a 15-year product warranty, and the two are separate. Read each in writing before signing.