Comparing solar panel brands
What the efficiency ratings and warranties mean, and what to look for beyond the spec sheet.
Panel manufacturers compete heavily on efficiency ratings and warranty terms. This guide helps you read those numbers clearly — and understand what else is worth considering.
What efficiency actually means
Panel efficiency is the percentage of sunlight that is converted into electricity. A 22% efficient panel generates 22W per 100W of sunlight hitting it. Higher efficiency means you need less roof space to achieve a given kWp — which matters if your roof is small. But high efficiency does not automatically mean higher quality. An average-efficiency panel from a well-established manufacturer may outlast a high-efficiency model from a newer entrant.
Product warranty vs performance warranty
There are two separate warranties. The product warranty covers the physical panel (defects, failure) — 10–15 years is standard, 25+ years is a premium sign. The performance warranty guarantees that after 25 years the panel still produces at least a stated percentage of its original output — typically 80–87%. A steeper degradation curve in the early years followed by a gentler slope is normal; check both the shape and the floor.
Tier 1 vs Tier 2 brands
The 'Tier 1' classification (from Bloomberg NEF and others) originally assessed bankability — whether a manufacturer was creditworthy enough that finance companies would back projects using their panels. It has since become a loose proxy for quality in consumer conversations. It is a useful starting point but not a substitute for checking actual warranty terms, installer experience with the brand, and the manufacturer's operational history.
What to check in a quote
When a quote includes panels: look up the manufacturer's current warranty document (not the installer's summary). Check the company has been trading for at least five years. Confirm the panels are made (not just branded) by the manufacturer. Ask your installer how long they have used that brand and whether they have seen any field issues.
Key takeaways
- Higher efficiency means less roof space needed, not necessarily better quality.
- Check both the product warranty (physical failure) and performance warranty (output degradation) separately.
- Tier 1 status is a useful starting point, not a quality guarantee — check the manufacturer's actual track record.
- Ask your installer how long they have been using the brand and whether they have had any field issues.
This guide is for general information only. It is not a substitute for a survey of your home or professional advice. Solar Help Centre does not install solar equipment or produce the final design for your home.
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