As Frank mentioned, a lot dependson the distance between your shop and the existing panel, you need to start by figuring your max load in the shop. Then size the conductors and conduit to provide that power at an acceptable voltage drop. It should not exceed 3%. Closer to 2% is better, 4% MIGHT be acceptable IF your max load will seldom be reached.

You can size the conductors you need here. Voltage Drop Calculator

A 120VAC circuit needs 3 conductors. For example if you decide you need 15 amps or 120 power, 100 ft from your existing panel. You need 2 -#10 conductors, and a #10 ground wire. That is 300 feet of copper wire. Right now a 500ft roll of #10 THHN stranded copper is about $140. You will have over $100 in 3/4" PVC conduit and fittings. You need a breaker to tap your existing panel, and should have a shut off in your shop. that is another $100-$200. You are already at almost $500 and you have not installed any outlets, etc for the equipment.

If you need more current, you need bigger wire. The price goes up exponentially. if you want 20 amps, you need #8 wire at 100 ft. That bumps your wire cost up to $270 for 300' of wire.

Only you can decide the route that makes the most sense for al of your variables.


Good Luck