Democratic presidential candidate Hillary Clinton has promised that if she’s elected she’ll make sure half a billion solar panels are installed in the U.S. by then end of her first term as president. That’s enough to power 25 million homes, she claims.

The announcement sent shockwaves through the media, and pundits speculated whether Clinton’s solar goal was even possible. The real question, however, is not the feasibility, but is her solar panel goal even that big of a deal?

To find out, The Daily Caller News Foundation crunched the numbers and found that Clinton’s solar plan will only be enough to power American homes for about four and a half weeks — and that’s only when the sun is shining. So, it’s probably not going to do much in terms of energy abundance, but it will likely cost a lot of taxpayer dollars.

Now, Clinton’s plan comes out to about 140 gigawatts of installed solar power capacity by the end of 2020. That’s a huge increase from the current 19.6 gigawatts of installed photovoltaic solar capacity, but it’s still way short of what the U.S. requires to meet its basic electricity needs.

Solar power has its advantages, but it’s no substitute for traditional energy sources because of its intermittency and reliance on sunshine. Not to mention solar power is still costly and relies on government support to be economically viable. That said, TheDCNF still endeavored to estimate just how much power would be generated by Clinton’s plan.

The average American home uses about 10,908 kilowatt hours (kWh) of electricity every year, according to the Energy Information Administration. Census Bureau data shows there are about 115.9 million housing units in the country that are occupied by owners and renters — not a perfect estimate, we know, but let’s run with it.

Using this as a starting point, U.S. households use about 1.3 million gigawatt hours of electricity every year. Hillary’s 140 gigawatts of solar power would produce 1.2 million gWh of electricity if there was 24-hour sunlight. But the sun doesn’t shine for 24 hours a day, and it varies greatly by region and time of year.

San Diego, Calif., for example, gets about 3,055 hours of sunshine per year, while Washington, D.C. only gets about 1,783 hours of sunshine per year. TheDCNF took the average number of sunshine hours from 47 states and D.C. and came up with 2,721 hours of sunlight in the U.S. in a year.

With that in mind, the power generated by Clinton’s solar panels would be 380,940 gWh per year. But then that assumes all panels are working at 100 percent capacity — which is never the case. To correct for this, TheDCNF factored in the average capacity factor of photovoltaic solar panels. According to EIA data, that comes out to about 28 percent.

Adding this into the equation means half a billion solar panels would generate only about 105,901 gWh per year. That’s only about 8 percent of American household energy needs for one year.

Put another way, Clinton’s solar plan will only generate enough electricity to power American homes for about four and a half weeks out of the year. Even this number is likely generous because it assumes all power needs throughout the day can be met by solar, but solar doesn’t generate power at night. The evening is generally when electricity demand spikes.

So maybe during one month of the summer time, Clinton’s panels would generate enough electricity for America’s homes, but this estimate doesn’t include a whole host of issues like rooftop space, siting issues, where the sun is coming from and other particulars that can weigh down on solar panel efficiency.

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