How long do solar panels last?

Solar panel lifespan is an important question but its answer is only gradually becoming clear.

The first point to make is that some of the first PV panels on the market are still out there, pumping electrons, after 35 years or so. That tells us we have yet to find an upper limit to their lifespan.

The second is that the output of any panel diminishes gradually over the years, so ‘how long a panel lasts’ may depend on what percentage of its original output we can tolerate losing.

And the bottom line is that PV panels will often outlast their first owner’s need for them.

The long, slow decline

The (generally useful) Solar Calculator website says that…

…solar panels degrade slightly each year and output diminishes by between 0.3 – 1.0% per year. …
The best solar panels degrade at just 0.3 – 0.4% each year, meaning that after their 25-year warranted lifespan, they operate at up to 90% efficiency when compared to their first year. [At 40 years they will still produce 85%.] …
Inferior modules degrade more quickly at rates up to 1% each year; after 25 years, these panels will produce just 78% of the electricity that they did when first installed. [At 40 years they will still produce 66%.]

These figures are confirmed, more or less, by a big comparative study conducted for a testing authority in USA ten years ago. They may look bad at first glance but they only mean the difference between getting a small cheque from the power company every quarter, and giving them one – after 25 years! Most of us would remember that the system paid for itself 20 years ago and simply shrug.

Not just panels

Solar Calculator also notes that, “Solar panels may have a lifespan greater than 25 years, but this does not necessarily mean your system will last that long,” and talks about the lifespan of inverters and mounting racks.

It doesn’t talk about the lifespan of the building to which the PV system is attached, but perhaps it should. Over 25 years, a house is likely to have new owners, a new roof, extensive renovations, or all three. And any one of them is enough to prompt a rethinking of the PV system.

It doesn’t talk about technological change, either, or social and legislative change. Again, perhaps it should. How much of our daily life is the same now as it was 25 years ago? Will the next 25 bring more change, or less?

As I said above, the bottom line is that PV panels will often outlast their usefulness in their original location. What will happen to them then?

Blue-sky dreaming

It’s possible that we will see the emergence of a market in used panels.

Imagine, for instance, that a solar farm wanted to off-load a paddock full of ten-year-old panels to make space for a big battery. Sending the panels to landfill or recycling would net them no return at all. Selling them in small lots to local businesses, who wouldn’t mind a 10% cut in output if they could get a 50% cut in price, would be far better for them. Or they could export the components of the whole farm to an outback town – or a developing nation – for a mini-grid. Again, the price would be right.

The informal market may be much more diverse, as this oldish discussion on Whirlpool suggests. And beyond that,  this slightly tongue-in-cheek article suggests that most old panels need not go to landfill.

Black-sky dreaming

Whether or not this will happen, the facts about the lifespan of panels reveal that recent media  fuss about used PV panels and the waste they represent is excessive.

One could almost believe, in fact, that it was a disinformation campaign fomented by fossil fuel interests as an attempt to undermine faith in solar power. Would they do such a thing?

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