It's low cost and it is also easy to install in many types of systems. No maintenance required at all! The only issue that I have found is the noise produced by this system but not so much as a big problem for me while using them in my house. They are very efficient as energy storage for our solar panels. We've been able to store more power into these units then we could use from them during off peak hours which has saved us money every month. We have been using vanadium redox for several years now to store solar energy as well as provide backup power supply during times that there is no sun/solar radiation in our area. No issues so far! The only drawback I found was at the beginning where we had some trouble getting it right but since then everything has gone smoothly (at least from my side). If you are looking into storing electricity generated by renewables (power plants) this seems to be your best choice out here in California.