Prices for new wind and solar plants continue to plunge at an astonishing pace.

Driven by steadily improving technology and the use of auctions to set prices, the cost of solar and wind dropped 25 percent this past year — and even more in some key emerging markets like China.

That drop comes on top of an 80 percent reduction in the previous 10 years, which is why building new renewable energy sources is now cheaper than just running old coal and nuclear plants.

China’s electricity price on a solar deal for Inner Mongolia plunged 44 percent last year. And solar module prices dropped 26 percent.

Auctions have been driving down renewable energy prices everywhere they’ve been used. In a Saudi Arabian auction last month, solar crushed its own record for cheapest electricity “ever, anywhere, by any technology” — so much so that the lowest price for solar power last year is the highest price now.

At the same time, renewable technology just keeps improving. For instance, wind turbines today can generate the same power in an 11 mile-per-hour wind that turbines a decade ago required a 22 mph wind for.

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