First, some background...Installed a HPWC last March when I took delivery of my MS. My house is newer construction with 200A service and most of our major appliances are gas. Our local utility does not have off-peak pricing. Due to all this, since the day we got the car we plug it in upon returning home and it charges at 80A. Zero problems. Even on a hot summer day with the AC running. Fast forward 10 months to a few weeks ago. January 27th I'm on treadmill, TV on, wife was working on a project in the kitchen, Model S charging...power goes off. I go out and our main breaker tripped. Important detail...the main whole-house breaker tripped...not the dedicated 100A breaker that the HPWC is on. It took about 4 minutes of flipping it on and off before it would turn back on. I guess it had to "cool" down. I figured that maybe we finally hit the 200A max (although in my head it made no sense) so I set the car to charge at 1am. All is good for the next week. 1:37am on February 2...power goes off. Obviously everyone was sleeping and the only thing that "on" was the Tesla. I realize at 2am and flip the main circuit back on at 2:10am. Main circuit tripped again at 3:05am. At this point I went into the Model S and changed it to charge at 60A. Works fine for a few days... February 5...main circuit trips again. Same thing...takes 5 minutes or so for the main circuit to reset. Electrician scheduled to come out February 13. I set the car to charge at 40A. Charges fine for a few days... Last night at 11:40pm...main circuit trips again this time with the car at 40A. ARG. So...it can't be an overload problem since it has charged fine for 10 months at 80A and now it's tripping even at 40A. My theory is that the main breaker has "gone bad" but my electrician who is coming out on Friday is skeptical..."it's possible for a main breaker to go bad, but rare." OK, here's the reason for the title of this post. In most of the scenarios above it tripped with less than 10 minutes of charging left. Last night it had 6 minutes of charging left. I'm assuming it's more about the heat/power build up over time (or something) and it trips at the end of the charge, but just wanted to make sure the unit itself doesn't actually "do" anything toward the end of charging that would cause this problem. I'm looking for help as obviously my electrician doesn't have years of HPWC experience! Thanks for any thoughts!