I have four front load washers connected, they all use the same water supply line and while there are two sets of electrical outlets, they are all on the same circuit. Honestly I don't know at this moment how many amps the breaker is, it's more than likely a 20 Amp circuit. I have all four running at the same time regularly and never have a problem.

I have also had four vintage top load washers connected and running at the same time. As long as the motors for each washer don't start at the exact same moment, it's not been a problem. The one "wrench" in the works however is when I also have the 1955 Unimatic connected. It's usually no problem, but if the other three vintage machines are running and the Unimatic does into spin, that WILL pop the breaker.