Solar panel types, and the four numbers that actually matter

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.

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. A Jinko Tiger Neo 435W sits around £60 to £85 at trade prices, roughly half the per-panel price of top-tier back-contact panels at similar output. Aiko carries a 10% to 15% per-watt premium over comparable N-type rivals. Whether that premium buys you anything depends entirely on whether your roof is space-constrained.

Where the mainstream brands sit

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.

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.

How to compare two quotes in five minutes

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. Installations themselves are carried out by an MCS-certified installation team for your area.