Solar Panel FAQ: Wattage, N-Type, Efficiency and How Many You Need

Solar panels are sold on a handful of numbers and a lot of cell-technology jargon. This guide answers the questions we hear most, whether you are looking at Jinko N-type modules or a LONGi back-contact panel — the reading applies to any brand.

What does the wattage on a panel mean?

A panel's wattage (e.g. 440 W, 590 W) is its output under standard test conditions — full, direct sun. Modern residential panels sit roughly in the 400–620 W range depending on physical size. Higher wattage per panel means you fit more generation in a given roof area, which matters on smaller or complex roofs. But wattage alone is not quality: two panels of the same wattage can differ in efficiency, low-light behaviour and how slowly they degrade.

How many panels will I need?

It depends on your usage, roof and goals, but a common Australian home system is around 6.6–10 kW of panels. At ~440 W each that is roughly 15–23 panels; at 590 W each, fewer. If you plan to add a battery or an EV charger, size up — the cheapest kilowatt-hour is one your own roof made. An installer works back from your bill and roof orientation rather than a panel count.

What is N-type TOPCon, and why does everyone mention it?

N-type TOPCon is the current mainstream upgrade over older P-type (PERC) cells. In plain terms it means higher efficiency, better performance in low light and heat, and slower degradation — so the panel produces more in early morning, late afternoon and summer heat, and holds more of its output over 25+ years. For most Australian roofs it is the sensible default today.

What about back-contact (BC) cells?

Back-contact technology moves the wiring to the rear of the cell, so there are no metal lines shading the front. That lifts efficiency further (some modules reach ~24–25%) and gives an all-black look many people prefer. It sits at the premium end — worth it when roof space is tight and you want maximum output per square metre.

What is dual-glass construction — is it better?

Dual-glass panels sandwich the cells between two sheets of glass instead of glass and a polymer backsheet. They are more resistant to moisture, fire and micro-cracks, often carry a longer warranty, and degrade more slowly. They are a little heavier, so the racking and roof are checked accordingly — routine for a good installer.

How efficient are modern panels, and does efficiency matter?

Module efficiency (around 21–25% today) is how much of the sunlight hitting the panel becomes electricity. Higher efficiency means more power from the same area — it matters most when your roof is small or broken up by hips, vents and skylights. On a large, simple roof you can reach the same total with slightly cheaper, lower-efficiency panels.

How long do panels last, and how fast do they degrade?

Quality panels carry a product warranty of 15–30 years and a performance warranty of ~25–30 years, typically guaranteeing they still produce ~87–92% of their original output at year 25. N-type and back-contact panels degrade more slowly than older cells, especially in the crucial first year. Compare the year-1 and year-25 numbers, not just the headline length.

Can panels pair with a home battery?

Yes — panels generate the energy, a battery stores what you do not use during the day for the evening peak. The two are designed together: your total panel size, inverter and battery capacity are matched so the battery fills on a normal day without wasting generation. See how to choose a solar battery and kW vs kWh explained for how size and storage relate.

Ready to compare? Browse solar panels or talk to Sunbridge — we design the array around your roof, your bill and any battery or EV plans.