Okay matey,
Watts=voltsxamps
W=vI
Say you're in the UK:
v=230volts (Not sure for USA, I think they're on 110V?)
Most household circuits breakers flick at 15-50 amps depending on what they're designed to accommodate, Ovens etc. are on a separate circuit for safety that can take more current(something we as growers should replicate in our grow room designs) .
Say a single socket circuit in your has a breaker that breaks at 20A. By rule of thumb you shouldn't load these more than 80% for a long period because of fire risks.
I=20A
W(total)=230*((20/100)*80)
W(total)=230*16
=3680w (UK)
=1760w (US)
So on a single domestic circuit you can get away with 3680W in the UK. I'm no electrician so don't take this as fact.
Also Keep in mind though you will probably already have loaded the one you're using with other appliances. Know what circuits go where.
If I were you, I'd pay a qualified electrician to install a fresh circuit to my grow room with a high amperage breaker. Say up to 50A.
That way I'd be sure it wasn't going to overload or cause fire and another advantage is:
Say my fan is on a separate breaker that overloads and my fan turns off. I'm out all day so my lamps cook my room. Not good for anyone. If I had them wired in my breaker at least the lamps would shut off too.