Choosing solar panels comes down to five things that actually matter: efficiency, warranty length and terms, degradation rate, manufacturer track record, and whether the panel and installer are MCS certified (which you need for VAT relief and most grants). Wattage and aesthetics matter too, but they’re secondary decisions once those five are settled, and most UK homeowners are better served picking a well-reviewed mainstream panel than chasing the highest efficiency number on the spec sheet.
Start With MCS Certification: Non-Negotiable
Whatever else you decide, both the panel and the installer need to be MCS (Microgeneration Certification Scheme) certified – this is required for 0% VAT relief, most grant schemes, and the Smart Export Guarantee. It’s an easy thing to check and rules out a lot of the riskier, cheaper offers you might come across, since a genuinely MCS-certified installer has met a recognised technical and consumer-protection standard.
The Five Things That Actually Matter
| Factor | What to look for |
|---|---|
| Efficiency | 22%+ is a solid mainstream standard; only pay a premium for 24%+ if roof space is genuinely limited |
| Warranty | 20–25 year performance warranty; check what percentage of output is guaranteed at year 25 |
| Degradation rate | Under 0.5% per year is good; some premium panels claim under 0.4% |
| Manufacturer track record | Established manufacturers with a UK/European presence tend to honour long warranties more reliably |
| Certification | MCS certification for both panel and installer, plus standard IEC product certifications |
Efficiency: Don’t Overpay for It
Mainstream TOPCon panels now sit at 22–24.8% efficiency, which is more than enough for the vast majority of UK roofs. Premium back-contact panels pushing towards 25% cost more per watt and only earn that premium back if your roof space is genuinely constrained – our guide to the most efficient solar panels available covers this trade-off in more detail. For most homes with reasonable roof space, a mainstream-efficiency panel and a slightly larger array works out better value than a smaller number of premium panels.
Warranty Terms Worth Actually Reading
A “25-year warranty” can mean different things depending on the manufacturer: check specifically what percentage of original output is guaranteed at the 25-year mark (commonly 80–87%), whether the product warranty (covering manufacturing defects) matches the performance warranty in length, and whether the manufacturer has a UK or European entity that would realistically still exist to honour a claim decades from now. A shorter but more credible warranty from an established manufacturer is often a safer bet than a longer one from a brand with no local presence.
Practical Factors: Size, Weight and Appearance
Physically larger, higher-wattage panels mean fewer panels for the same total capacity, which can reduce installation labour and mounting hardware, but they also weigh more per unit and need enough clear roof space to fit their dimensions around any obstacles. All-black panels (with a black frame and backsheet rather than the traditional silver frame and blue cell colour) cost a little more but are widely preferred for kerb appeal, particularly on more visible roof slopes.
How Much Say Do You Actually Get?
Most installers quote using a small number of panel brands they work with regularly, rather than offering the entire market, and that’s not necessarily a bad thing – it usually reflects panels they trust and can service. It’s still worth asking directly why they’ve specified that particular panel, what the warranty terms are, and whether a different tier (budget, mainstream, premium) is available if your priorities differ from their default recommendation.
Frequently Asked Questions About Choosing Solar Panels
Is a more expensive solar panel always better?
Not necessarily. Price often reflects efficiency, brand reputation and warranty terms, but a mainstream panel from an established manufacturer frequently offers better value than a premium panel whose extra efficiency you don’t actually need for your roof space.
Does the panel brand matter more than the installer?
The installer generally matters more for how well the system performs and whether problems get fixed properly, since installation quality affects everything from output to roof safety. Panel choice matters most for long-term degradation and warranty security, so both are worth getting right rather than treating one as more important.
Should I choose all-black panels?
It’s a matter of preference and budget rather than performance – all-black panels look neater to most people and are widely chosen for that reason, but they don’t generate more electricity than a standard silver-framed panel with the same underlying cell technology.
How many different panel brands should I compare?
Comparing two or three genuinely different options (checking efficiency, warranty and manufacturer reputation for each) is usually enough to make an informed choice without getting overwhelmed by minor spec differences that won’t meaningfully affect your results.
