Bought several of these to remotely monitor inverters but found them very useful for measuring performance. The logger measures the energy produced by the solar panels and the energy produced by the inverter every hour and stores the data and the app allows you the view the data in graphic format for an entire month at a time, among other things.
Easy to set up with my Android phone but had problems trying to set up with my Android tablet for some unknown reason, but it works well with the tablet once it is set up.
