A 15 amp circuit can carry only a total of 1440 watts,which is 80% of the 1800 watts found by mulitplying the volts times amps,15 x 120 x 80%= 1440.
CODE stats should only run at 80% as to reduce fire danger
so you're only using 150w of 1440w so you could add what you need, just if you put 1400w be aware what else runs off that breaker, so they all do not run at the same time