| Chances are the circuit is wired up with # 12 wire and you could safely change to a 20 amp breaker. If you can get a look at the right place on the wire, it will say something like 12-2 with ground. If it is only 14 gage, stick with the 15 amp breaker.
I wouldn't worry about the gas range and microwave. Most gas ranges only have a light and a timer that draw very little current. |