100 Amp Main Panel

[hiya]

I have a 100 amp main panel (can be upgraded to 130) . I currently have 12 enphase m250 inverters with 315 watt panels. I am going to add 16 m215 enphase inverters with 265 watt panels. That would put max output at 27 amps. Most people i know who have had there solar installed have had there main panels upgraded. Is this a tactic to up sale or necessary? 6 panels face south, 14 will face west and 8 will face east so i assume they wont be at peak output all at once for that long.

[inetdog]

If you are subject to the National Electrical Code (NEC) it does not matter when the various panels and microinverters will be producing power, just what their rated output is.

You add up the rated output current at your line voltage from the specification of each inverter and multiply by 125% to get the current number to use in the next calculation.
You then multiply the current rating of the main panel bus bars (at least 100A, and in some cases perhaps 125A) by 120% and subtract the amp rating of the main breaker feeding the panel bus. That number must be greater than or equal to the first number you calculated for the PV output amps.
With a 100A panel with a 100A bus, the PV number must be less than (100 x 1.20) -100 = 120 - 100 = 20A. Note that if the micros are set up for 240V, you count the amp number against both bus bars. If the micros are set up for 120V, then you could have up to 40A of calculated PV input, with 20A being connected to each of the two buses in the panel.

If that condition is not met, then one solution is to upgrade the main panel, say to 200A, and then put in a main breaker smaller than 200A. that will allow for 40A of PV plus the difference between 200 and the new main breaker rating.