Solar panel types, and the four numbers that actually matter
Panel brochures are a wall of numbers, most of which do not change your bill. Four of them do. Here is what each one means and where the current mainstream brands actually sit.
Updated 29 October 2026 · written by the Clearline guidance team · 6 min read
Three cell technologies, one race
Almost every panel quoted to a UK home in 2026 uses one of three N-type cell architectures. They differ in how the electrical contacts are arranged and what the cell is layered with, and that drives efficiency, cost and how gracefully the panel handles heat.
- TOPCon is the mainstream cost-efficiency choice across most manufacturers in 2026. Jinko's Tiger Neo and Trina's Vertex S+ are both N-type TOPCon.
- HJT, or heterojunction, layers crystalline silicon with thin amorphous films. REC's Alpha Pure-RX is the best known HJT module on UK roofs.
- Back contact, sold as ABC, XBC or HPBC depending on the maker, moves all the electrical contacts to the rear of the cell so nothing shades the front. Aiko and Longi lead here.
Back-contact modules now lead efficiency at close to 25%, ahead of HJT and TOPCon. TOPCon remains the volume choice because it delivers most of the performance for materially less money. Neither of those facts tells you which is right for your roof, which is the point of the rest of this guide. For the long version of how back contact works, and what it does and does not change on a UK roof, read back contact solar panels, explained.
- Cell technology
- HPBC 2.0, n-type wafer, busbar-free
- Construction
- Dual glass, bifacial
- Module efficiency
- 23.5 per cent at standard test conditions
The four numbers worth comparing
1. Module efficiency
Efficiency is how much of the light landing on the panel becomes electricity. It matters most when roof space is tight, because a higher efficiency panel fits more capacity into the same rectangle. If you have a large clear roof, efficiency is a much weaker argument than price per watt.
2. Temperature coefficient
Every datasheet publishes a figure like -0.26% per degree. It tells you how much output the panel loses for each degree the cells sit above test conditions. A lower number is better, and the spread across the mainstream is real but not dramatic: REC quotes -0.24%, Longi -0.26% and the Jinko Tiger Neo platform -0.29%.
3. Warranty terms, plural
There are always two warranties and they are not the same thing. The product warranty covers the physical panel against defects. The performance warranty guarantees a minimum share of the original output at a given year. Mainstream N-type panels in 2026 carry 25 to 30 year performance warranties guaranteeing 87% to 92% of original output at end of term. Product warranty terms vary by series and by market, and are the number most often misquoted, so read the datasheet for the exact model on your quote.
4. Price per watt
The honest one. TOPCon panels sit at a lower cost tier than top-tier back-contact panels at similar output. Whether the back-contact premium buys you anything depends entirely on whether your roof is space-constrained.
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Where the mainstream brands sit
| Brand and line | Cell type | Residential wattage | Efficiency | Notes |
|---|---|---|---|---|
Aiko Neostar 3 | N-type ABC back contact | 485W (1762 mm) and 535W (1954 mm) | 24.3% at 485W, 24.1% at 535W | No front grid lines; product warranty 15, 25 or 30 years by series |
Longi Hi-MO X10 | HPBC 2.0 back contact | 480 to 500W | 23.8% at 485W | Cell-level shading design bypasses only shaded cells |
Jinko Tiger Neo 54HC | N-type TOPCon | 420 to 460W | 21.52% on the 440W all-black | 30-year linear power warranty, first-year degradation 1% or less then 0.4% a year |
Trina Vertex S+ | N-type i-TOPCon, dual glass | 440 to 475W | 22.5% at 450W | 25-year product and 30-year power warranty |
JA Solar DeepBlue 4.0 | N-type | 440 to 455W | Up to 23% | 25-year product warranty, 30-year performance to 87.4% |
REC Alpha Pure-RX | HJT heterojunction | Up to 470W | 22.6% | Lead-free all-black. ProTrust cover up to 25 years including labour when fitted by an REC Certified installation team |
Specifications from manufacturer datasheets and UK distributor listings, accessed August 2026. Warranty terms vary by SKU and market, so confirm against the datasheet for the exact model quoted to you.
The panel is rarely the reason a system underperforms
Across this table the efficiency spread is roughly 21.5% to 24% and the temperature coefficients differ by 0.05 percentage points per degree. Roof orientation, shading, inverter sizing and how much of your generation you actually use yourself all move your bill far more than the badge on the module.
All-black panels and what they cost you
All-black modules, with black frames and black backsheets, are the default aesthetic request in UK residential. Several mainstream lines offer them directly: the Jinko JKM440N-54HL4R-B is an all-black 440W TOPCon module, and the REC Alpha Pure-RX is a lead-free all-black build. The trade-off is usually a small efficiency step down against the same manufacturer's standard-frame equivalent, because a black backsheet runs slightly hotter.
If the roof faces the road and the house matters to you, take the all-black. If it faces the back garden, spend the difference on another two panels. That is a genuinely better use of the money, for reasons we set out in why half filling a roof costs more.
Panels are half the decision
The other half is what converts and conditions the power. On a clear single-aspect roof a plain string inverter is usually the right answer. On a complex or shaded roof, module-level electronics earn their keep. We compare all three approaches in microinverters, optimisers or a plain string inverter, and the full picture on kit selection sits on our solar panels guide.
Worth knowing: some modern back-contact panels now handle partial shade better on their own. The Longi Hi-MO X10 uses a cell-level shading design that bypasses only the shaded cells rather than dropping a whole section of the panel, which weakens the blanket claim that any shade requires optimisers on every module.
Bring your quote to a free design call and we will read the datasheets with you, line by line, and tell you what the differences are worth on your roof.
Get my free quote →How to compare two quotes in five minutes
Find the exact model number
Not the brand. A brand sells six lines with different cells and different warranties. The model number is the only thing that lets you compare like for like.
Compare total kWp, not panel count
Twelve 500W panels and fourteen 430W panels are not the same system. Multiply wattage by count and compare the totals.
Check both warranties separately
Product cover and performance cover run for different terms. Write both down for each quote.
Divide price by kWp
This is the single most useful number for comparing quotes, and it lets you see what you are paying for a premium panel.
Every county page on this site carries a calculator built for that area, so you can put your own roof and usage into the model before you speak to anyone. Start at your county page. Every system is installed and commissioned by our own MCS-certified, fully insured installation teams.
Choosing panels, answered
Which solar panel brand is best in 2026?
There is no single answer, because the right panel depends on how much roof you have and how much of it is shaded. Back-contact panels from Aiko and Longi lead on efficiency and cost the most per watt. TOPCon panels from Jinko and Trina deliver most of the performance for materially less, which makes them the volume choice when roof space is not the constraint.
Is a more efficient panel worth paying for?
Only when roof space limits your system size. If a higher efficiency panel lets you fit 6kWp where a cheaper one fits 5kWp, the premium is buying you real generation. If the roof is large enough for either, the same money buys more panels of the cheaper type, which produces more electricity overall.
What is the difference between TOPCon and back contact?
TOPCon is a cell structure with a passivated rear contact layer and conventional front busbars. Back contact moves all the electrical contacts to the rear so nothing shades the cell face, which is why back-contact modules reach close to 25% efficiency. Back contact costs more per watt; TOPCon is the 2026 mainstream cost-efficiency choice.
What does a 30-year performance warranty actually promise?
It guarantees a minimum share of the original rated output at year 30, not that the panel will still make 100%. Mainstream N-type panels guarantee 87% to 92% at end of term, with first-year degradation of 1% or less and around 0.4% a year after that. It is a floor, not a forecast.
Do all-black panels perform worse?
Slightly, in most ranges, because a black backsheet runs a little hotter and panel output falls as cell temperature rises. The difference is small enough that most homeowners choosing on appearance are making a reasonable trade. It is worth checking the specific efficiency figure for the all-black variant rather than assuming it matches the standard version.
Does Clearline install these panels?
Yes. We offer a free remote design call, and every system is installed and commissioned by our own MCS-certified, fully insured installation teams. We name manufacturers here purely so you can compare quotes on the facts rather than on sales patter.
See the numbers next: LONGi 530 W panels, installed, or the solar panels guide.
Figures and specifications in this guide are sourced below and were checked on the date shown. Rates and product specifications change; we confirm the current picture on your free design call.
Sources
- Aiko Neostar product range and wattage bands aikosolar.com
- JA Solar, Aiko and Longi comparison, efficiency, warranty and per-watt pricing spectrumenergysystems.co.uk
- Longi Hi-MO X10 HPBC specification: 23.8% at 485W, -0.26% per degree qualityheating.co.uk
- Longi Hi-MO X10 cell-level shading design solenenergy.com
- Jinko Tiger Neo specification and 30-year linear power warranty jinkosolar.com
- Jinko JKM440N-54HL4R-B all-black 440W listing, 21.52% efficiency midsummerwholesale.co.uk
- Trina Vertex S+ NEG9R.28 datasheet, 22.5% at 450W, 25-year product and 30-year power warranty pluginsolar.co.uk
- REC Alpha Pure-RX: HJT, 22.6%, -0.24% per degree, ProTrust warranty terms recgroup.com
- Cell technology ranking: back contact close to 25%, ahead of HJT and TOPCon cleanenergyreviews.info
- Best solar panels UK 2026, indicative trade pricing per panel smartsolarhomes.co.uk
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