Solar panel types and efficiency explained

Solar panel spec sheets are full of acronyms. The good news is that almost every panel sold for Canadian homes today is a mature, reliable silicon product, and the differences between them are smaller than the marketing suggests. This guide translates the terms so you can compare quotes with confidence.

Mono vs poly

Older guides spend a lot of time on monocrystalline vs polycrystalline panels. That choice has largely disappeared. Monocrystalline silicon is now the industry standard, and polycrystalline panels are rare in residential quotes. If a quote in 2026 offers polycrystalline panels, ask why.

The cell technologies, in plain terms

Panels are built from cells. The cell design is what the acronyms describe.

PERC

PERC (passivated emitter and rear cell) adds a reflective layer to the back of the cell so it captures more light. It was the mainstream technology for years. Manufacturers are now phasing it out in favour of newer designs, though PERC panels still work well.

TOPCon

TOPCon (tunnel oxide passivated contact) uses a thin layer on the back of the cell to reduce energy losses. It is now the most common technology for new panels. TOPCon panels usually perform a little better than PERC in heat and low light.

Heterojunction (HJT)

Heterojunction cells layer thin films of amorphous silicon on a crystalline silicon wafer. They tend to handle heat especially well and age slowly. They usually cost a bit more.

Back-contact

Back-contact cells move all the electrical contacts to the rear of the cell, so the front has nothing blocking the light. They currently reach the highest efficiencies on the market and have a clean, all-black look. They are typically the priciest.

How they compare

An industry review of modules listed from 2024 to 2025 found top commercial efficiencies of about 24.8% for back-contact, 23.7% for TOPCon, 23.5% for heterojunction and 21.7% for PERC. Typical panels in a residential quote sit a little below those maximums.

Bifacial panels

Bifacial panels collect light on both sides. On a flush-mounted roof, the back side sees very little light, so the gain is small. They make more sense on ground mounts or raised flat-roof racks over a light surface, where reflected light, including from snow, can reach the back. See ground-mount and flat-roof solar.

Efficiency vs wattage vs price

These three get mixed up.

• Efficiency is the share of sunlight hitting the panel that becomes electricity. A higher number means more power from the same area.
• Wattage is the panel's rated output, such as 420 W. A bigger panel can have high wattage without high efficiency.
• Price for comparison purposes is best measured per watt of the whole system. See how to compare solar quotes.

What you pay for is total kWh over the years. Two systems of the same kW size, in the same spot, will produce about the same energy whether they use 21% or 23% panels. The more efficient system just uses less roof.

When efficiency matters

Efficiency matters most when roof space is the limit.

• Small or broken-up roofs, such as townhouses, homes with dormers, or roofs with only one good face. Higher efficiency fits more kW in the space you have.
• Homes with high use, such as those with an electric vehicle or a heat pump, that want to cover as much as possible from a modest roof.

On a large, unshaded roof with room to spare, mid-range panels often give the best value per dollar.

Temperature coefficient

Panels lose a little output as they heat up. The temperature coefficient on the spec sheet tells you how much, as a percentage per degree Celsius above 25°C. A smaller number (closer to zero) is better. Newer technologies such as TOPCon and heterojunction generally have better figures than older PERC panels.

In most of Canada this matters less than in hot climates. Cold, sunny spring days are when panels perform best. See solar in Canadian winters.

What to look for on a spec sheet

• Wattage and efficiency
• Cell technology
• Temperature coefficient of power
• Product and performance warranty terms
• A recognized Canadian certification mark, such as CSA
• Snow and wind load ratings, which matter in heavy-snow regions

Brand names

Many manufacturers make good panels, and the same factory may build several brands. We don't recommend specific brands. Focus on the specs, the warranty and whether the manufacturer has a clear way to handle claims in Canada. See solar warranties explained.

Next step

Check your roof to see how much space you have and how many kW it can hold, or try the system size tool.

Common questions

What is the most efficient type of solar panel?

Back-contact panels currently reach the highest commercial efficiencies, at about 24.8% in a 2024 to 2025 industry review. TOPCon and heterojunction panels are close behind at about 23.5% to 23.7%.

Is TOPCon better than PERC?

TOPCon usually performs slightly better, especially in heat and low light, and is now the mainstream choice. PERC panels still work well but are being phased out.

Do I need high-efficiency solar panels?

Only if roof space is limited. On a large unshaded roof, standard panels produce about the same energy per kW and often cost less per watt.

Are bifacial panels worth it on a roof?

Usually not on a flush-mounted roof, because little light reaches the back. They make more sense on ground mounts or raised flat-roof racks.

Sources

• TaiyangNews: TOP SOLAR MODULES 2025 report highlights
• pv magazine: ITRPV, global module shipments reached about 706 GW in 2025
• Electrical Safety Authority: Recognized approval marks