Black solar panel performance in Australia

Buy the black panels. The performance gap that used to make them a bad idea has effectively closed, the price gap at wholesale is now small, and a solar array is on your roof for twenty years in full view of the street. Two numbers on the datasheet tell you whether a particular black panel is any good.

Derek on panel appearance

From an interview with Markus Lambert of Your Energy Answers:

I love black solar panels. In the past there was an argument that black solar panels would retain more heat. The better looking that you can make a solar system on a house, the better.

If it can enhance the value and appeal of your home with a minimal performance detriment, then go for it. They are so close in specifications now. There used to be a wider gap but now there’s not.

Markus made the point that lands hardest: there is no sense saving five hundred dollars and living with a twenty-thousand-dollar house that looks worse for it. That is the real trade, and for most people the aesthetics win on a roof facing the street.

We even include full black mounting hardware because it will complement the black frame. Once you put an all-black solar panel on it, it looks good.

Efficiency and temperature coefficient

Module efficiency. How much of the sunlight hitting a square metre of the finished panel becomes electricity, at Standard Test Conditions, counting the whole module rather than the cell in isolation. Higher is better. Twenty-two per cent or above is a strong design and the figure is comparable regardless of the panel’s physical dimensions, which is what makes it useful.

Watch the wording. Cell efficiency is always higher than module efficiency and it is not what goes on your roof — the module figure accounts for the frame, the gaps between cells and the internal circuitry. A brochure quoting cell efficiency without saying so is quoting a number you cannot buy.

Temperature coefficient of Pmax. How much output the panel loses for every degree above 25 ℃. Lower is better, and it is expressed as a negative percentage per degree. This is the one that actually matters in Perth, because a roof here is nowhere near 25 ℃ on a February afternoon — panel temperature routinely runs 25 to 30 degrees above ambient. A panel losing 0.26 per cent per degree and one losing 0.35 will perform noticeably differently on the day you most want the output.

Backsheets and heat

It was the backsheet. Older all-black panels used a solid black backsheet that absorbed heat behind the cells with nowhere for it to go, and the panel ran hotter and derated further. That was a genuine performance penalty and it is why the advice used to be to take the silver frame and the white backsheet.

Semi-transparent black backsheets changed it. They keep the appearance while letting the panel shed heat closer to the rate a conventional module does. Combined with better temperature coefficients across the board, the penalty on a good modern all-black panel is small enough that it is not the deciding factor any more.

The limits of paying for appearance

On a roof nobody sees. If your array is going on a back-facing pitch behind a two-storey, you are paying for something you will never look at, and the money is better in the inverter or the battery. Same on a shed or a workshop.

And a black panel does not rescue a bad specification. A cheap all-black module with 19 per cent efficiency and a poor temperature coefficient is a worse buy than a good conventional one, no matter how it looks. Check the two numbers first, then decide on appearance.

The panels we currently fit, with their datasheets, are in the solar range. For a layout worked out against your own roof and which pitches actually face the street, ask for a written price.