We recently installed an 8kw ground mount pv system with battery back up for a customer in Johnston County. Now his refrigerator, well pumps, kitchen, living room and bed room circuits all off the grid. All other circuits are still powered by the utility however his solar system should net zero or come close to zeroing out his annual electric bills because any extra energy that is produced when his batteries are full is exported to the grid and credited against his monthly electric bill. He has a great application in that the solar panels are facing due south in a field with sun all day long!
We used mono crystalline black Axitec panels, the schletter pv racking system, SMA inverters and smartformer. If we had to do it again I would probably research different racking systems to use. The schletter racking is good but I felt it was extremely over designed. We had to drill 24 inch holes 6 and a half feet deep and fill it with concrete. That’s a lot of concrete! At least its not going to fly away! My concern is that in many places you may hit rock before you get that deep so a different design would be preferable. The SMA inverters are always great but SMA really needs to come out with a 240V battery inverter so we don’t need to use the autoformer. Outback and other have battery inverters that output 240V however those models would need to be located out in the field near the solar panels or we would have had a huge voltage drop getting to the house which was nearly 200 ft away.
Going truly off the grid is a big undertaking and customers should know what to expect. Everything takes longer and it more complicated than a traditional grid tied pv installation. As a rule of thumb costs are generally double for a off grid system as opposed to a grid tied pv system of the same size. This varies a lot depending on the system size, types of inverters, types of batteries, storage and on and on.
Below are some photos of the installation and a quick video blog showing the system. Enjoy!