What is the wire size for 150 amp service?

Accordingly, what size wire is needed for 125 amp service?

If you have a 125 amp breaker you need 125 amp wire. See the table here. You need to use the 75° column since no one makes a 90° breaker just yet. Since this is a single phase dwelling service you can use #2 AWG copper or 1/0 aluminum for a 125 amp service or main feeder.

Subsequently, question is, what is the wire size for 100 amp service? You need a 3-3-3-5 copper SER cable to carry 100 amps (that's three #3 gauge for the two hot wires and the neutral and a #5 gauge for the ground). If you want to use aluminum, you need at least #2 gauge or perhaps #1.

Simply so, what size wire do I need for a 200 amp service?

So, for a 200-amp service, you would still be allowed to choose a 4/0 AWG aluminum or 2/0 AWG copper, but you would choose it from the 75 degree C column in Table 310.15(B)(16).

What size wire do I need to feed a 100 amp subpanel?

A 100 A sub-panel requires a two-pole 100 A breaker - if you want 100 A. You can use #4 AWG 75 deg C or 90 Deg C copper wire in conduit for a 100 A breaker provided the breaker is labeled for use with 75 deg C wire.