MxRider2637,
If your friend doesn't already have three phase power, it can be very expensive to install. In my case, the transformers alone would have cost $7500. Then, to run three phase power from the next road would have cost an additional $30000. And no, you don't get to take the transformers to your next house, even though you paid for them.
If this is a residential account, there may be a motor horsepower limit. My power company will not allow single phase motors over 7.5 horsepower. I don't know how they would know, but they said they'd cancel my service if I used a motor larger than 7.5 hp. So, if you're using a rotary phase converter, be aware of that. Also, some power companies won't allow three phase power on residential accounts.
But, if you're just asking about a three phase motor versus single phase, and your friend already has three phase power, three phase motors may be cheaper than single phase motors.
