I was having a bit of a difficult time understanding the requirements on the electric panel when a solar PV system is connected. I was under the impression that my 100 Amp service wouldn’t meet code requirements, but I wasn’t sure why.
Well, here is the story. NEC 690.64(B)2. That is the section of the National Electrial Code.
The concern is that you can’t have a situation where the utility current (100Amp) plus the solar array (30 Amp) is more than 120% of the rated capacity. Well 100+30=130 which is more than 100 X 1.2 = 120 so that doesn’t work. And it makes sense.
So here is the panel I think I’m upgrading to: My New Ann Arbor Load Panel (Note that this panel is also being set up for generator interlock and that is the topic of that particular article.)