Great information from the other members already. I will echo some of the benefits.
There are different ways to configure your system. The power from the PV (Photo-voltaic panels) goes into you house and whatever is not used runs your meter backwards as it goes out into the grid (simplistic explanation). The power from the PV goes into your house and whatever is not used goes into batteries (big ones). If you run out of electricity in your batteries and if you installed an easy switch option, you can switch over to the utility grid. You have options on how to configure, is basically what you need to consider. And as already stated, the PV will still produce electricity, albeit in a diminished amount, on cloudy days.
I am an architect and we have been installing more PV on commercial buildings. Do look into local and federal tax credits as these may still be available. There is also the option to allow the utility company to install them on your home, no upfront cost to you. They would own and maintain the panels, but you do not get as much bottom line savings.
Look for a local PV company. They can walk you through your options, design the systems, etc.
Good luck.
Hank Recor
Westwood, MA, USA
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Feel the Burn.......