Wire Cost

About

• NM-B house wire is specified for 60C by the NEC, but it can withstand 90C. [1]
• 2AWG is rated for 95A at 60C, 1 AWG is rated for 110 at 60C [2]
• USE-2, RHW-2 and RHH - sunlight, heat, moisture resistant [3]
• Aluminum ampacity - 1/0 aluminum does 100A at 60C. Good chart of wire types and their T resistance [4]
• Terminations at panels must be rated at 60C - [5] - thus you must specify wire for 60C. For example, if you want 100A, oversize 100A 90C wire to something larger at whose 60C rating you get the required ampacity.
• THHN to subpanel - yes if in conduit - [6]
• Standard practice - individual THHN through conduit or NM-B through stud holes [7]
• Romex or BX wire can be run without conduit - [8]
  • Romex goes up to 2 awg [9]

Subpanels

• Since 2008, 4-wire cable is required. [10]
• SER cable is preferred, no conduit needed [11]. XHHW and THHN can be used but require conduit.

Cost

• THHN 6 ga copper - $1/ft [12]
• 6/3 NM-B is $5/ft [13] or [14]
• 2/3 NM-B is $9/ft [15]
• 4/0 is same price - [16] or [17]
• 1/0 aluminum URD is 100A and $2.50/ft [18]
• 2/0 aluminum SER is $4/ft [19]
• 1/0 aluminum SER is $3/ft [20]. $5/ft after shipping for 16'.