It is a photovoltaic (PV) system interacting with the utility, with or without batteries, that uses a relatively new breed of inverters that can actually sell any excess power produced by your solar array back to the utility grid. If you are concerned at all about your utility rates going up and would like to do something to reduce your monthly electric bill, then a grid-tie solar system may be just the thing for you. These systems are easy to install and since some do not have batteries for back-up, the lack of batteries in these systems means no messy maintenance or replacements to worry about. The solar modules can be mounted on your roof or out in the yard, where they sit quietly generating power from the sun that you can either use directly or sell back to the utility company.
If that sounds pretty interesting, you might want to look into what it would take to install a grid-tie PV system. The first thing you should do is contact your utility company to see if it will allow you to connect a solar system to its electrical grid. While there is a national law that requires investor-owned utility companies to allow interconnection of a solar or wind power system, rural electric cooperatives are exempt from this law. If your utility company will allow you to connect your PV system to its grid, the next question to ask is if it will buy the energy back at the retail or wholesale rate. Ideally you want the utility company to buy back any excess electricity that you produce at the same retail rate that you buy electricity. This is called “net metering” and is the simplest way to setup a grid-tie PV system. In such a system you only have one utility kWh meter that spins in either direction, depending on whether you are buying or selling energy. In a non-net-metered system, the utility company will require that you install a second kWh meter to record any excess energy to be sold, and the company only pays the wholesale rate (usually only a few cents per kWh). To find out if your state offers “net metering” or any other incentives for installing a renewable energy system, click on the following link (www.dsireusa.org).
Remember, a “net metering” law for your state doesn’t necessarily apply to rural electric cooperatives, so give your utility company a call before going any further.
The next step is to figure out what size system will work best for you. This is tricky because it all depends on how much energy you want the system to produce per day, what your utility rate is per KwH and of course how much money you want to spend on a system. Your location is a big factor in determining how much energy any grid-tie PV system will produce, since everybody knows that Las Vegas gets a lot more sunshine than Seattle. The higher your utility rate (¢ per KwH), the more economical a grid-tie PV system becomes, since you are offsetting expensive energy that you would have bought from the utility company with clean free energy from the sun.
more details about off-grid systems and articles