under the carpets DUH THATS DANGEROUS AS HELL , ALMOST AS HOT. extenison cords are made to be in open air.
Like some one said OHM's law is not for attorneys, but the right to live.
One more common factor the fire department will call the cops when they find out you growing pot.
Watts = volts x amps never exceed the total for a given feed/wall outlet
In any grow always have a smoke dectector and replace battery often.
Multi extension plugs are always a extreemly chance for a fire.