Is TOPCon really better than PERC for a home?

For lifetime energy, usually yes. N-type TOPCon reaches higher module efficiency (up to about 23% versus about 21.5% for PERC), has a better temperature coefficient so it loses less power on hot days, performs better in low light and cloud, and degrades more slowly over 25 years. PERC's advantage is a lower upfront price and the longest field track record. If budget is the deciding factor and roof space is plentiful, PERC is still a sound choice; if you want the most energy over the system's life or your roof is tight, TOPCon usually wins.

When are bifacial panels worth it for a house?

Only when the back of the panel can see reflected light. Bifacial modules add up to roughly 25% rear-side gain on ground mounts, flat roofs with a light-coloured surface, carports and snowy sites, where fresh snow reflects strongly. Flush-mounted flat against a dark pitched roof they see almost nothing, so you have simply paid for heavier double-glass panels with no benefit. For most standard pitched roofs, monofacial PERC or TOPCon is the better value.

Which panel is best if my roof is small?

N-type TOPCon. Because it packs more watts into the same area (up to about 23% efficiency, with panels up to 620 W), you fit more kilowatts on a limited or awkward roof. On a small roof that difference can decide whether the array covers your consumption or falls short, which is why our designer leans to TOPCon when roof area is the constraint.

What do the wattage numbers like 555 W and 620 W mean?

They are the panel's rated peak output under standard test conditions. Our PERC line runs 400–555 W and our TOPCon line 420–620 W; a higher number means more power from one panel, which usually also means a physically larger panel. What matters for your home is total array size — daily kilowatt-hours needed against your location's sun hours — not any single panel's wattage. The system designer works that out for you.

What are flexible, foldable and snow-melting panels for?

They are purpose-built for jobs a rigid glass rooftop panel cannot do. Flexible panels (50–400 W) are about 2 mm thick and bend to a curve, for van and boat roofs or weight-limited surfaces. Foldable panels (60–400 W) pack down and carry USB and MC4 outputs for camping and emergency power. Snow-melting panels (50–400 W) have a built-in heating film to clear snow in cold regions. They complement a rooftop system rather than replace it.

Do I have to choose the panel technology myself?

No. Tell us your roof, location and consumption in the system designer and it will spec the panels for you — technology, wattage and count — alongside a matched hybrid inverter and storage, and return a complete indicative design in about two minutes. You can send that straight to us for a quote.

PERC vs TOPCon vs bifacial — how to choose solar panels for your home

Almost every home solar quote today lands on one of three cell technologies: monocrystalline PERC, N-type TOPCon, or a bifacial version of TOPCon. The datasheets look similar at a glance — same silvery rectangles, watt figures a few percent apart — so it is easy to pick on price alone and miss the reasons the numbers differ. This guide explains what actually separates them, and which one belongs on which roof.

We build the Senneon solar line around these technologies, from 30 W custom modules up to 620 W, so the panel is matched to the job rather than sold as one-size-fits-all.

Don't want to compare datasheets? Tell us your roof, and our system designer will spec the panels, inverter and storage for you in about two minutes — and pick the panel technology that fits your site.

The three technologies at a glance

	Mono PERC (P-type)	N-type TOPCon	Bifacial TOPCon
Module efficiency	up to ~21.5%	up to ~23%	up to ~23% front, plus rear gain
Temperature behaviour	good	better — loses less on hot days	better
Low-light / cloudy yield	good	better	better
First-year & long-term degradation	standard	lower	lower
Extra yield from reflected light	no	no	yes — up to ~25% from the back
Relative cost	lowest	moderate	highest
Best for	budget rooftop, proven value	high-yield rooftop, tight roofs	ground, flat and snowy sites

Everything below is the reasoning behind that table.

Mono PERC — the proven, high-value baseline

PERC (Passivated Emitter and Rear Cell) is the P-type monocrystalline technology that carried the rooftop market for years, and it is still the sensible default when the goal is the most reliable watt per euro. Our monofacial PERC line runs 400 W to 555 W with module efficiency up to about 21.5% — the 555 W panel weighs around 27 kg on a roughly 2.28 × 1.13 m frame. It is a half-cell design, which lowers the heat-spot risk and helps in partial shade, and it is engineered to meet IEC standards with an anti-PID build and a mechanical rating of 2400 Pa wind and 5400 Pa snow load. The performance warranty is the industry norm for the class: at least 92% of rated output at year 12 and at least 84.8% at year 25, on a 10-year product warranty.

Choose PERC when budget is the deciding factor, roof space is not tight, and you want a mature technology with the longest field track record. It is the panel our designer specs by default for a straightforward pitched roof.

N-type TOPCon — more energy from the same roof

TOPCon (Tunnel Oxide Passivated Contact) is the N-type successor, and it wins on the metrics that decide annual yield rather than just peak watts. Our monofacial TOPCon line runs 420 W to 620 W with module efficiency up to about 23% — the 620 W panel fits on a roughly 2.38 × 1.13 m frame at about 28 kg. Three real advantages over PERC:

A better temperature coefficient. Panels lose power as they heat up; TOPCon loses less. On a hot summer roof — exactly when you are producing most — that gap turns into real extra kilowatt-hours.
Stronger low-light performance. It starts earlier in the morning and holds up better under cloud, which matters in northern Europe far more than a sunny-day peak figure suggests.
Lower degradation. Less first-year loss and a gentler long-term decline mean more energy across the 25-year life.

Because it packs more watts into the same area, TOPCon is also the answer when roof space is the constraint — you fit more kW on a small or awkward roof, which can be the difference between covering your load and falling short.

Choose TOPCon when you want the most energy over the system's life, your roof is limited, or your climate is hot, hazy or cloudy — and you are willing to pay a moderate premium for a lower cost per kilowatt-hour over time.

Not sure which pays off on your roof? The system designer sizes the array to your consumption and your country's sun hours, so you can see how many panels — and which technology — your site actually needs. Tell us your roof, we'll spec the panels.

Bifacial TOPCon — harvesting light from both sides

A bifacial panel is a TOPCon module built as double glass so the rear side also generates, capturing light reflected off the surface beneath it. Our bifacial line shares the 420 W to 620 W front rating of the monofacial TOPCon panels and adds a rear gain of up to about 25%, depending entirely on how reflective the ground below is. The trade-off is weight and mounting: the double-glass 620 W panel is around 33 kg versus about 28 kg for the monofacial version, and it only pays off when the back of the panel can actually see reflected light.

That makes bifacial a site-specific choice rather than a universal upgrade:

Excellent on ground mounts, flat roofs with a light-coloured membrane, carports, and snowy regions — fresh snow is one of the most reflective surfaces there is.
Wasted flush-mounted on a dark pitched roof, where the rear glass sees almost nothing and you have simply paid for heavier panels.

Choose bifacial when you have a ground array, a bright flat roof, or a site that spends real time under snow — anywhere the rear face has a reflective surface to work with.

How to choose: roof, budget, scenario

The decision usually falls out of three questions:

What is your roof? A standard pitched roof with room to spare → PERC for value, or TOPCon if you want maximum lifetime yield. A small, shaded or awkward roof where every square metre counts → TOPCon. A ground mount, a bright flat roof, or a carport → bifacial.
What is your budget horizon? Lowest upfront cost → PERC. Lowest cost per kilowatt-hour over 25 years → TOPCon, and bifacial where the site rewards it.
What is your climate? Hot, hazy or cloudy, or a limited roof → TOPCon earns its premium fastest. Reliable snow cover or high ground reflectance → bifacial.

There is no universally "best" panel — only the best match for your roof, your budget and your site. That is exactly the judgement our designer automates.

Special-purpose panels: flexible, foldable, snow-melting

Beyond the three mainstream rooftop technologies, the Senneon line includes specialist panels for jobs a rigid glass module cannot do:

Flexible panels (50–400 W) are a semi-flexible mono build only about 2 mm thick — roughly 80% lighter than a double-glass module and able to bend to a curve. They are made for surfaces that cannot take rigid framed panels or their weight: van and RV roofs, boats, and curved or load-limited structures. Note this is a lightweight PET/ETFE construction with a shorter rated life than a glass rooftop module, so it is a purpose choice, not a cheaper rooftop substitute.
Foldable & portable panels (60–400 W) fold down for transport and carry DC, MC4, USB and USB-C outputs — the panel you take camping, overlanding or into an emergency kit to keep a portable power station, fridge or devices charged off-grid.
Snow-melting (heating) panels (50–400 W) add a built-in heating film that warms the surface to clear ice and snow quickly. In high, cold, snow-prone regions, snow sitting on a panel is lost production; a heated module keeps generating when a plain one would be buried.

These are additions to a rooftop system, not replacements for it — the right tool where a standard panel does not fit.

How the panel fits the rest of your system

A panel is one piece of a matched set. Whatever technology you pick, it feeds a hybrid inverter — sized to your peak load, not just your panel wattage — and, in a self-sufficient setup, a battery that stores the day's surplus for the evening. For a site starting from scratch, a complete off-grid solar system bundles panels, inverter, storage and balance-of-system so the parts are matched from the start rather than assembled from mismatched boxes. You can browse the full solar panel range to see the technologies and power classes side by side.

The practical point: array size depends on your daily kilowatt-hours and your location's sun hours, and the inverter and storage have to match it. That is a system calculation, not a single-panel one.

The short version

PERC is the proven, best-value baseline for a straightforward roof. TOPCon gives you more energy from the same area — better in heat, better under cloud, better over 25 years — and is the pick for tight roofs and demanding climates. Bifacial adds rear-side generation and belongs on ground mounts, bright flat roofs and snowy sites. Flexible, foldable and snow-melting panels cover the jobs a rigid rooftop module cannot.

Or skip the comparison entirely: tell us your roof and our system designer will spec the panels — technology, wattage, count, inverter and storage — and return a complete indicative design you can send straight to us for a quote.