You are sizing an array. Two panels in your cart hit the same wattage at roughly the same price. One says N-Type TOPCon. The other says Mono PERC. Which one goes on the roof?
Short answer: either will work. The N-Type panel will produce a little more power over 25 years, especially if your site runs hot. The P-Type panel costs less up front and has a longer track record. Neither is a bad call.
The longer version is worth knowing, because the panel aisle of every solar shop is now half N-Type and half P-Type, and the spec sheets do not make it obvious what the trade is.
What the labels mean
Both panels are silicon. The wafer inside a cell has two layers, one positive and one negative. The label refers to which layer faces the sun.
In a P-Type panel the positive layer is on top. It has been the standard for decades. The manufacturing line is mature, the supply chain is huge, and the panels are cheap to make.
In an N-Type panel the negative layer is on top. It is harder to manufacture, which is why N-Type costs more, but the resulting cell behaves better in a few ways.
Where N-Type wins
The first thing is degradation. Every panel loses a little output every year. P-Type panels typically lose around 2% in year one and about 0.55% every year after. N-Type panels lose closer to 1% in year one and 0.4% per year after. Over 25 years that is the difference between roughly 84% output and 88% output. Not huge, but real.
The second is heat. Panels lose efficiency as they get hot. The temperature coefficient on a typical PERC panel is around -0.35% per degree C. On an N-Type TOPCon panel it is closer to -0.29%. On a Florida roof in July that adds up.
The third is low light. N-Type cells produce a little more power at dawn, at dusk, and on cloudy days. Small effect, but visible in the production curves.
There is a fourth thing worth mentioning. Most N-Type panels today are dual-glass and bifacial, picking up reflected light off the back side. You will see anywhere from 5% to 25% extra production depending on what is behind the panel. P-Type bifacial panels exist too, but the everyday P-Type module is still mono-glass.
Where P-Type still makes sense
Price. A 400W P-Type panel runs $85 to $125. A 400W N-Type panel runs $130 to $180. On a big array the per-watt difference matters.
Track record. PERC cells have been in the field for fifteen years and we know exactly how they age. N-Type TOPCon has only been mass-produced since 2022. The accelerated tests say they will last as long, but we do not have the field data yet.
Replacement panels. If you are matching an existing array, stay with the same cell type. Mixing N-Type and P-Type in a series string usually works, but it is a check-your-inverter-MPPT-range situation, not something to do casually.
What we stock
P-Type, Mono PERC: SunPower 405W, Canadian Solar 375W, Canadian Solar 395W.
N-Type: Solarspace 580W, Waaree 585W TOPCon, Alps 650W.
If your roof has the space and you want to build for the next 25 years, an N-Type module is the call. If you are watching the budget or replacing a panel in an existing string, the P-Type modules will get the job done.
Still not sure? The system builder picks a panel that fits your roof and your budget, and you can swap the model on the review screen before checkout. Or go straight to the panel aisle and filter by cell tech.