I live off the grid about 625 miles down on the Baja Ca peninsula. I see units go bad all the time. I have the same units as these except they are not the grid units. The unit that went bad. I know there is at least one shorted power transistor. I suspect there may it might have took out other things. I called the factory and they don't support that old of unit. I was seriously thinking of purchasing new units until I ran across these. If they work, then it would work out for me. That wouldn't be the case for many people. The charge controllers are two small for me to use. I'm currently producing 3.2k. I have a 80amp controller that works fine. Last year I changed out all my solar panels and upgraded them. Before I had 36 panels producing about 1.2k. They were almost 20 years old. About 5 years ago the old 60amp charge controller burned up and I replaced it with the new one. I have 4 105amp lithium car batteries, which runs the power for the whole house. We have sun most of the time. If I'm careful I can get 3 days of power without a recharge. I will say the most common thing that makes the controllers go bad is heat, as with most things electronic. The fans go bad. Down here in the summer it reaches about 100 degree's with about 150 percent of humidity. I have found the Outback system are one of the best well built units out there.