New energy codes in most areas will require you to use an energy efficient motor now, unless you can prove that the application is so specialized or runs so seldom as to make that impractical. In fact most motor shops will just provide you with an energy efficient motor now without asking unless you specifically call for a non-EE replacement motor.
What kwired said is a real issue that people often encounter when installing new EE motors as a result of this change. The mag trips on motor starter breakers often cannot hold in at the same settings, and then sometimes they cannot even be turned up high enough and you have to bump up the breaker frame size. The NEC makes allowances for this now in that if you prove that a setting will not work, you can increase the mag trip to 17x the FLA (it used to be 13x). But breakers usually stop at 10x the frame rating, so if you are at the ragged edge of a breaker frame size, you can get in trouble. I don't think that will happen to you at 15HP though.
