Breakers are sized for the wire, not the "end user". If you have all 15A breakers, chances are you have #14 wire. You can only go up in size on a breaker if you increase the size of the wiring. In order to go to a 20A breaker you need to go up to #12 wire. The only safe way around this (without rewiring) is to split your christmas lights to several different circuits.
Dude- Circuit breakers are sized upon the wire size. If you replace a 15 with a 20, your'e reducing the safety margin engineered into the Code.
I wish I new I'm looking to add a new circuit to handle all my lights.(christmas that is.)
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