Solar batteries—are they really green?

I have 10 kilowatts of solar panels on the rooftop of my home in Santa Monica, Calif. — enough to power my energy needs most of the time. Instead of selling excess power to the grid (and buying energy at night when the sun isn’t shining) I’d like to install batteries in the garage, storing enough energy in daylight to power my home when it’s dark.

I’d be off the grid and would also have a great backup system when the inevitable “big one” hits my state and the grid goes down. Taking my home off the grid would also reduce greenhouse gases and other polluting emissions that are created by the grid energy I use today. So this is a good — and green — concept for everyone? Well, not exactly.