when the device temperature is over than 45C, then the device block the generate to grid to protect the device(with 550W panel when device temp was 53C with 25C outdoor temp the generate power blocked at 200W, when putted ice on device and the temp was below 40C then the generate gone again at 530W), the efficiency is at 90% at 530W.
I think it need better and bigger heatsink because on summer with 40C outdoor temp then it could not work.