You have to size it right. My spark chaser friend said too much trouble to add up all the loads.
His trick is to turn it all on. Washer, dryer, oven, heat pumps, well pump and use a clamp on ammeter on each leg of the feed into the panel.
It ended up being a smaller number that I was figuring the sum of all loads way. He did it a couple of times to catch the start up loads as well. Like when the compressors in the heat pumps kick on.
Good luck!
His trick is to turn it all on. Washer, dryer, oven, heat pumps, well pump and use a clamp on ammeter on each leg of the feed into the panel.
It ended up being a smaller number that I was figuring the sum of all loads way. He did it a couple of times to catch the start up loads as well. Like when the compressors in the heat pumps kick on.
Good luck!