This is a off grid system; it will not feed back to the grid and stick it to the electric company. Well, it does stick it to them as I haven't had an electric bill since installing it in August of 2012. If you are trying to feed back to the grid or you are just trying to reduce your electric bill, look into a grid tie system using Solar AC Modules. These are easy DIY installs but they may not work as an emergency backup and you may have to jump thru some hoops with your electric company. My intent is to build a practical self contained electrical system or as some folks would refer to as a doomsday system.
The photo at the left is the power room which supplies all electric power to the house and the well. The solar electric power is being supplied by a single 135 watt solar panel mounted on the roof. The storage capacity of the AGM batteries is about 375 amp/hours. The charge controller can support a 30 amp imput and any number of additional batteries can be added should demand increase.
This system uses two modified sine wave inverters; one 3500 watt 115 VAC for the house lights, small appliances, and electric tools; which includes saws and a cement mixer. Heating for the house does not use any significant electrical load and we do not normally run a refrigerator or freezer.
The second inverter is a 5000 watt 230 VAC unit to power the well. Fortunately the well at this location is on a fairly shallow water table and the running current is 230 VAC @ ~6.5 amps. I installed a 85 gal well pressure tank on a 40/60 switch which gives ~43 gallons of usable water between cycles and has a recharge time of about 3 minutes. The well pump can also be run from a generator by a simple switch selection.
The charge controller has a 30 amp maximum charging rate, capable of logging amp/hours in and out.
This site does not have a lot of electrical demands, mostly lights, a microwave, coffee pot, and running the occasional power tool. Pumping water from the well is the big issue. Using a 5 gal/min sprinkler head has not proven to be a significant load on the system with a ten minute well pump cycle. On a full charge, it ran for several hours without depleting the batteries; however, it is reaching the capacity of the batteries and I am considering adding another solar panel for a faster charge time. I installed a drip system for 70 grape vines at a .5 gal/hr rate; the current system is handling that without an additional power requirements.
After one year, the only problems I have run into is heavy use of electrical tools and running the water hose full open causing the well pump to cycle frequently. With a charge rate of 7-9 amps during peak sun hours, it takes a while to recover.
So far this system has cost about $2500 as a DIY project. The solar panel is rated at 25 years, the electronics are oversized and should last indefintely, the batteries should last 7-10 years before replacement based on current usage. It is located in southwest Missouri and while not located in the sun belt per se, works suprisingly well.
Five years on and the system has paid for itself. Other than a cranky inverter that doesn't want to cold start sometimes, the system is still providing me with all the power I need.
Some free advice, whatever that is worth
You can spend as much as you want on solar products; prices vary from vendor to vendor. The batteries I used, ranged from $199 to $350 for the same battery - shop around! It was cheaper to ship mine across the country than buy them at the local big box home improvement store. Don't skimp on an off grid system, a system that won't supply your needs is useless and money down the drain. Borrow or buy a clamp on ampmeter to determine your acutal needs and size accordingly.