Adding an a/c to upstairs of home, need to run power cable to main power panel. What size wire shoud l use?
Probably 10-gauge. Check the electrical rating plate on the unit; it will probably say something on the order of 25 amps at 240 volts. As long as it draws less than 30 amps, 10-gauge is fine (with a dual 30-amp breaker); if it takes more, use 8-gauge with a 40 amp dual breaker. If it draws less than 20 amps (not likely, but possible), you can get by with 12-gauge wire and 20 amp breakers.
