Solar panels are the part of your system you'll see every day for decades, so it pays to choose well. Yet many quotes in Cape Town and Gauteng list panels as a single line: a number of panels and a wattage. Here's what actually separates one panel from another, and what to ask before you sign.
Wattage Isn't the Whole Story
A panel's wattage (for example 580 W) tells you its output under standard test conditions. It's useful, but two panels with the same wattage can still perform very differently on your roof. What matters more is how much energy the panel produces over a year in real conditions: on a hot summer roof, in partial shade from a tree or chimney, and after 10 or 20 years of ageing.
Efficiency: More Power From Less Roof
Efficiency is the share of sunlight a panel turns into electricity. Higher efficiency means more power from the same roof space, which matters on smaller or oddly shaped roofs where every square metre counts. As an example, the Enersol Lumina BC black panel we use on our residential systems has a module efficiency of 22.45% at 580 W, according to its datasheet.
Shade: The Hidden Energy Thief
Shade from trees, neighbouring buildings or a chimney can drag down a panel's output far more than you'd expect. Back-contact (BC) panels move the electrical contacts to the back of the cell and are designed to keep producing under partial shade by isolating the shaded sections. That's one reason we prefer shade-optimised back-contact panels for leafy Cape Town suburbs.
Heat and Long-Term Ageing
All solar panels lose a little output as they get hotter and as they age. Good datasheets tell you how much. The Lumina BC datasheet, for example, lists 1.5% power degradation in the first year and 0.4% a year after that, and its design targets lower operating temperatures for better stability in hot climates. When you compare panels, ask for these numbers rather than relying on brand names alone.
Warranties: Read Both of Them
Panels usually carry two warranties, and they cover different things:
- Product warranty. Covers defects in materials and workmanship. The panels we install carry a 15-year product warranty.
- Performance warranty. Guarantees the panel will still deliver a set share of its rated power after many years. Ours carry a 30-year linear performance warranty.
A long product warranty only helps if the manufacturer and installer are still around to honour it, so it's worth checking who stands behind it locally.
Looks Matter Too
Your panels are on show for 25 years or more. Full-black panels with hidden busbars give a clean, uniform finish that blends into dark or terracotta roofs, like the rooftop pictured above. For larger roofs and commercial sites, we also use high-output bifacial panels, which can collect reflected light from the back as well as the front.
Don't Forget What Holds Them Down
The best panel in the world is only as good as its mounting. Every system we install uses mounting matched to your roof or site, including corrugated, IBR and Klip-Lok roofs, sealed and watertight, with leaks covered by our warranty. Ask any installer how they mount and seal, and who pays if the roof leaks.
Panels Are One Part of a System
Panels work together with your inverter and battery, so they should be chosen as part of one design. Whether you go with a Tesla Powerwall 3 or a Sigenergy system, we size the panels to match your usage, your roof and your battery. If you're comparing quotes, our guide on why solar quotes can look so different explains what to look for line by line.
Get Expert Advice
MLT Power has been installing since 1986 and holds a 4.9-star Google rating from 143 reviews. We're a Tesla Premium Installer, South Africa's first installer of the full Tesla range, and a Sigenergy Certified Installer. Send us your latest electricity bill or call 087 943 2299, and we'll design your system with a free, fixed-price quote.
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