go to your breaker box... it should have some sort of labels or diagram... then they should say 10,15,20 amp... multiply that by 120 is the amount of watts you can put on that circuit
How many amps do the typical house have? It's the original box when the house was built in the 70s, I'm sure it's worn out by now...
You probably have 100amp service. Many newer homes have 200amp service but not all.