I currently have a 200 amp main breaker box in my house and is completely full of breakers. I would like to add dedicated 20amp circuit in my bathroom so I can install electric heated flooring below my tile. What would be the best way to add circuit? I assume I will need to add some sort of a Auxiliary panel next to the main box.

Wow. Is your house an "electric" house... water heater, furnace, range dryer? How many breakers do you have in use now?

I assume I will need to add some sort of a Auxillary panel next to the main box.That's generally the drill. What is your level of experience with electrical work?

Can you use tandem breakers where you are? That may be easier than installing a sub-panel if your only talking about one circuit. Depends on if they are allowed in your area.

Djm,

Did you mean mini circuit breakers instead of tandem?

djm,

Did you mean mini circuit breakers instead of tandem?Tandem, mini, skinny, twin, space-saver,. all the same thing.

Also called half size.

My 2 cents.

Need to check the panel label, not all panels allow tandems, and some do not all allow many.