Not sure about US, yet some high current lanes (thinks of threephase ~400V x 36A; IEC 60502-1) in the households are actually made of Al, not Cu. They tend to be underground though, the wires in the walls are still Cu.
Cu is more conductive than Al so an Al wire has to have a cross section area about 1.56 times that of a Cu with the same current capacity.
But Cu is also denser than Al so the Al wire is only about 0.47 times the weight of the Cu wire.
Al is is much cheaper than Cu so the Al wire is only about 13% the cost of the Cu wire.
Here is a table of the conductivity (in units of 10^7 S/m), the density, and the cost of copper (Cu), aluminum (Al), silver (Ag), and gold (Au).
Cu Al Ag Au
Conductivity 5.96 3.5 6.3 4.1
g/cm^3 8.96 2.6 10.5 19.3
$/kg 9.03 1.2 1030 92100
Weight Cost Diameter
Al 49 7 139
Ag 110 12646 97
Au 310 3190000 121