Hi James,
It sounds like you are looking for a solar electric (PV) or wind system with batteries and a utility intertied inverter. The premise being that energy is stored in the batteries. If more energy is produced than used, it goes back into the grid. If you use more energy than you produce, then the grid supplies you energy. If the power goes out, you draw power from your batteries.
All that being said, you have a very large load to power! Any time you use the words 'continuous usage,' it's going to add up to a lot of energy. My understanding is that your 120 VAC circulating pump draws 2.8 amps. That's 336 watts continuous. (120 x 2.8 = 336). If the pump runs for 24 hours, that's 8064 watthours per day (8 kwh). If you choose to use PV power, in Michigan, your insolation (good sun hours) are about 5.5 in the summer and closer to 2 hours in the winter. Which means to power that pump alone, you would need more than 1500 watts of solar electric modules to power it in the summer. Probably close to 3 times that amount to provide power in the winter.
So...one option is to find out if you have a good site for wind - better than 10 mph average wind is what you are looking for, and you'll need to have a tower 30' higher than any obstruction within 300' of the turbine. You will likely need about 1/2 an acre of space to accommodate a turbine and guyed tower. Another option is to see if their is a DC powered circulating pump you can use that would draw significantly less energy. A more efficient pump would allow you to use less solar modules to power it.
Finally, if you haven't already, check out our "Learn" section to read more about each technology. There is a good article about determining the right RE source for you.
http://howto.altenergystore.com/The-Basics/c10/I hope this helps!
