This device is simple to wire up, but double-check, no, triple-check your wiring before you power it up as there does not seems to be any protection built in (not unusual for these types of current measuring devices). The worst thing about it is that the mounting tabs are designed for very thin panels, whereas most panels I deal with are at least 1/16" more. Double-sided tape on the back of the bezel solves that, but even the lip of the bezel is thin. I would say that the thin mounting tolerances would knock this down to a 4-star rating, but I feel that the price is so exceptionally affordable, that it makes up for it. I bought two of these for my RV -- one to monitor charging, and one to monitor discharging. Such an arrangement still cost less than other battery monitors, and I can now see (well, calculate, actually) my charging efficiency. I would rather calculate charging efficiency by hand than rely on some pre-programmed values because from what I know of deep-cycle batteries, each has their own voltage/state of charge (and discharge) characteristics and I think even the best battery monitors use a one-size-fits-all approach.