Solar power will be cheaper than fossil fuels at some point between the end of this decade and 2026*, said U.S. Secretary of Energy Steven Chu at the Washington Post's Smart Energy conference this morning. (For more on what Chu said, check out Guardian reporter Suzanne Goldenberg's tweets from the conference.)

The date at which solar power reaches "grid parity" with fossil fuels without subsidy has been the subject of heated debate for decades. (If you want the details, just yesterday I had a long discussion with Jesse Jenkins of the Breakthrough Institute about whether or not we're currently on the right path to make renewables competitive with dirtier sources of energy.)

Needless to say, solar at the same price as fossil fuels has the potential to completely transform the global energy market by making the switch to solar a no-brainer. You might even call it the Holy Grail of renewable energy technologies.

Chu could be wrong, but it's hard to imagine anyone in the U.S. better positioned to know the trajectory of the cost of solar power. Under Chu, the Department of Energy launched the ARPA-E project to fund advanced energy research, and some of its projects already have the potential to make a huge difference in the cost of solar panels.

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*Update: this post originally said "2016" which is incorrect.