Smoke came out trying to start a 1000w air conditioner. I'm not sure what kind of surge this AC creates at startup, but it destroyed the inverter when I first connected it to AC. There was a crackling sound, and then smoke came out of the inverter. I wish I had tried it when it first arrived rather than believing that once everything else was settled it would work. Mine will never do 4kW continuous and 8kW peak power. It's probably too late to send it back, so it's a total loss on first use. I'll probably reschedule the boat trip while waiting for another one to arrive (I'll buy another manufacturer's product to replace this one).