Photo: Flickr, CC
Probably a Similar Ratio in Other Cities
If solar panels were installed on the 2/3 of buildings in NYC that are suitable, around 50% of the city's electricity needs could be provided for when the sun is shinning. Of course, we're nowhere near that number right now - NYC has about 6 megawatts of rooftop solar at the present time - but the mayor's office and various groups including City University of New York (CUNY) are trying to get that number to go up with various tools, including tax breaks and an interactive highly-detailed map that gives info on solar energy in NYC (see below).
Photo: NY Solar Map
Above is a screen shot from the NY Solar Map. Try it out for yourself, it's pretty cool.
If NYC was to get a bigger installed based of rooftop solar, the biggest benefits would come during heatwaves like the ones we recently had. At those times, everybody fires up the A/C and it puts a huge strain on the power grid. Older and dirtier backup generators have to be fired up to cope with demand, and the grid becomes much more polluting for a time.
Photo: Flickr, CC
But the beauty of solar is that you usually have more of it available on the hottest days of the year. It's still much better to have buildings that are designed to require as little A/C as possible, or none at all, but it can't hurt to also increase the amount of clean power on the grid.
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