3 ms·Max sustained load on a 15A breaker is not 10A/1200w, it’s 80% of 15A at 120v, or 12A/1440w.by quickthrowman 4y agoMax sustained load on a 15A breaker is not 10A/1200w, it’s 80% of 15A at 120v, or 12A/1440w.