The only problem with upgrading the breaker is that it would be a Code violation if the panel's bussbars are only rated at 100 amps.If there is a 100 amp rating stamped somewhere inside the panel, I would not put the larger breaker in. Some people imagine that a 200 amp service delivers “better” electricity than 100 amps.The service size, however, indicates nothing more than the maximum current you can draw through your electrical system at one time.
Some forums can only be seen by registered members.The new line is important, as it needs to be thicker, so it can safely feed up to 200 AMPS, without overheating.You have to see if 200 AMP is available from the street/LIPA going into your house. The grounds would ave to be ripped up to run new lines.200 amps is unnecessary unless you literally have a mansion.This home was heated with a gas furnace, had a gas clothes dryer, a gas water heater, and a gas oven.The only major 240 volt appliance at this home was the air conditioner. Can you guess what the calculated service size was? Granted, my calculation probably wasn't perfect, and I'm not sure that this online load calculator was completely accurate, but this was enough to make me not worry about the service size.When I took an electrical inspection class many years ago, we had to perform a lot of load calculations for fictional houses, and I learned enough to know that if most of the major appliances are gas, a 100 amp service is probably plenty enough.