I am an electronics technician & computer geek so I understand basic electricity but am not an electrician. I want to run 52-feet of wire from main panel to subpanel off a 60-amp circuit breaker inside of PVC conduit. I have run 3/4-, 1- and 1-1/2-inch conduit. What is the safest and most energy efficient giage of wire to use?

First question, have you sized the load for this subpanel to make sure that 60 amp will meet your needs?

Are you bringing 240 or 120 VAC or both to the panel.

You would use a # "6/3" <corrected typo> AWG cable for 240/120 VAC.

Stan: Thanks for the catching my typo.

For a 60A sub-feed you would need at least #6cu.

Conduit. THWN 4 insulated conductors. Wire is usually dual rated THHN/THWN. Conduit buried so the top is 18" underground. For non-conduit 24".

I'm assuming a 240/120 sub-panel.

Ground rod is required for detached structure.