Minor heads up, most 15A circuits aren't able to pull an 1800w load. 15A is not the continuous load that the wiring and cb are rated for. 12A is...meaning you get 1440 watts max on a continuous load.
If this was true, houses would burn down and need to be rebuilt every couple of months. Eventually, people would figure out the problem and start putting 12 amp breakers in, or wiring capable of actually handling 15 amps. Oh, wait, we picked option 2 decades ago.
Watts isn't a meaningful term for talking about AC circuits, except that it is usually sorta close. The real amount of power that a circuit can deliver is measured in Volt-Amps. A 15 amp circuit can handle 1800 VA nominally, but if your voltage it is amperage that trips the breaker, not power, so if your voltage is low, you won't get as much power.