There are a few of problems with solar cells:

1) The sun only shines half of the time, at night the solar cells are worthless.

2) One could charge up a battery during the day with the solar cells and at night live off of the batteries, but for it to be practical and useful most of these batteries would have to be as big as the house, thus costing millions of dollars. And thus costing more than most houses.

3) Solar cells usually don't last long enough to justify their costs. So it is still cheaper and more practicle to use fossil fuels to produce energy than solar cells.

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