I was quoted $5000+ to upgrade my house from 100A electric service to 400A. Part of the reason for the high cost is the cost of copper. What size copper wire is needed for 400A, and how much does it cost per foot? Would it be a lot cheaper to use aluminum wire?Oh come on!! The question seems to be asking abotu replacing the service ENTRY cable to bump it up from 100 to 400 AMPS. Got news for you all. THe service entrace cable IS aluminum. It connects to the circuit breaker box at terminals designed FOR aluminum. Go take a look at any recent install and tell me what you see. (It will be AL) AS for the remainign wires throughout the house. Most will be copper. However note that modern outlets can be provided to accept aluminum and copper. Just look fot the AL/CU stamp ont he outlet. Generally the clothes dryer, over and A/C will use al wire but they are attached to outlets specifically designed for AL wire. EricYeah, aluminum isn\'t allowed in new or renovated construction. The size of cable needed for 400A will be determined by the service provider. Probably 4/0 size cable. New service means a new panel and new wiring. 14/2 is suitable for lighting and general receptacle use up to 15A, but 20A is required for all kitchen outlets, so use 12/2. If you use 12/2 throughout, be sure to use 20 amp breakers in the panel. Since 14/2 is only rated up to 15A, if you use 14/2 with 20 amp breakers, you run the risk of overheating and causing a fire.They can be joined but only through a suitable device marked specifically for aluminum to copper connections. See website below.Aluminum has been outlawed due to corrosion issues. Actually, that is a good price. As for wire gage, 14-2 will be adequate, but when I did my house, I insisted upon 12-2 through out. It doesn\'t cost that much more and you will avoid the possibility of overheating or over load issues.Other related question