China's Tongwei Group Plans World's Biggest Solar-Cell Plant (5GW/yr)

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34. You've been doing this for 25 years and don't seem to understand the basics of the warranty?

Something like 10 years ago I went to a seminar on solar energy locally. I have been a solar proponent since the mid-70's but this was the first time I understood the significance of the warranty period of solar panels. What at the time was 20 yrs and is now moving to 30 years. Basically they warranty the output at the stated time period - 80% of rated output for example. Since a solar panel has no moving parts this guarantee is not like that on the drivetrains of our cars which are under constant wear and tear during their use. It's a linear progression so that a panel with a guarantee of 80% at 25 years will still be producing 60% at 50 years. And that is the key. They don't just stop producing electricity if they have a valid warranty (implied quality manufacturing here). So when a system reaches the break even point where it has paid for itself there are still decades of free electricity to come.

Here's an example of what's happening in the industry now.

SunPower has recently updated their warranty (April 1st, 2013) and guarantees 95% of rated power for the first 5 years, declining by no more than 0.4% per year the following 20 years.[1] This means SunPower guarantees 87% of rated power output at 25 years – by far the best warranty on the market.
Yingli Solar`s Panda solar panels guarantees 82% of rated power output at 25 years.[2]

http://energyinformative.org/solar-panel-warranty-comparison/