One short, but interesting, article in the news for December 28, 2012 is “Exponential gains in solar efficiency could make it half the price of coal by 2030.” The article is at a website called “MINING.com,” which says it is “Your source for global mining news.”

The article looks back on an earlier article that appeared in March of 2011, in Scientific American, called “Smaller, cheaper, faster: Does Moore’s law apply to solar cells?” The author of that article says that the cost of PVs is declining exponentially, in the same way computer chips have. The rate of decline is 7% per year, which means the price is cut in half about every 9 to 10 years. A quote from that article is:

“The exponential trend in solar watts per dollar has been going on for at least 31 years now. If it continues for another 8-10, which looks extremely likely, we’ll have a power source which is as cheap as coal for electricity, with virtually no carbon emissions. If it continues for 20 years, which is also well within the realm of scientific and technical possibility, then we’ll have a green power source which is half the price of coal for electricity.”

Bear in mind that the article and the quote are nearly two years old, so 8-10 years means 6-8 years from now.

Some people ask whether it makes sense to wait to install solar, given the expected decline. I think the clear answer is no; it makes sense to install now, rather than waiting. If a person who can install solar now waits instead, he might get the solar power at a lower cost, but he certainly will pay for electricity in the meantime. The advantage of waiting is not fully known, and may not be great at all. One thing we do know, however, is that global warming is not waiting.