We have had a 2K Enphase system up and running since April of 2010. About a year and a half ago Enphase asked if we would like to have their new battery storage system installed on our system for them to monitor and test. This was at no cost to us. Of course we said yes. They installed 3 batteries in our garage that we control and monitor though an app to store energy during off peak and provide energy during on peak rate times. We looking to add 2 powerwalls and possible some more panels/inverters to our system. The enphase batteries do not provide any "back-up" function and I really want to have that available. We are having our site survey done today. Will update with results and recommendations later.