Basically, a 120v 15 amp circuit has the potential for 1800 watts. 120*15. Rule of thumb is to keep it around 80% of max or 1440 watts. That being said, 1500 watts on a 15 amp circuit would be okay. If you had 12 gauge wire, you could run a 20 amp circuit and get up to 2400 watts or 1920...