I live on Lake Lanier in Georgia. I want to run a power with a copper ground wire underground from my house to a floating dock 250' away to supply a 20 amp circuit. What type and size wire do I need to buy?

Just on the pure math, a 250' run of UF cable will require a size 4 AWG cable.

However, there is much more needed, not the least of which is weatherproof box, GFCI protection and probably more. I have never dealt with Marina or dockside installations.

I am sure someone can give a much better answer than I.

My calculator, Southwire, shows a #6 will give you 20 amps with 3.69% voltage drop. You do not want to exceed that drop value. As Don notes, #4 would be optimal but more costly.

Just on the pure math, a 250' run of UF cable will require a size 4 AWG cable.

However, there is much more needed, not the least of which is weatherproof box, GFCI protection and probably more. I have never dealt with Marina or dockside installations.

I am sure someone can give a much better answer than I.

Thank you very much. As I looked more indepth I found the regulations for a GFI and weatherproof box.

Thanks again, Techie2u

My calculator, Southwire, shows a #6 will give you 20 amps with 3.69% voltage drop. You do not want to exceed that drop value. As Don notes, #4 would be optimal but more costly.

Thank you this was a help.
Techie2u

Type UF like Don mentioned can be buried directly in dirt; another option would a conduit with individual conductors.

You might consider using a GFIC breaker to avoid nusiance tripping caused by condensation getting into a GFIC receptacle. They make nice single twist-lock receptacles that form a weather resistant seal.

I'd also consider running the underground portion to the shoreline, into a weatherproof disconnect switch. Then continue to the dock using either #12 extra-hard usage type SO cord, or liquid-tight flex with indivdual conductors inside. Everything needs to be designed for wet locations.

Type UF like Don mentioned can be buried directly in dirt; another option would a conduit with individual conductors.

You might consider using a GFIC breaker to avoid nusiance tripping caused by condensation getting into a GFIC receptacle. They make nice single twist-lock receptacles that form a weather resistant seal.

I'd also consider running the underground portion to the shoreline, into a weatherproof disconnect switch. Then continue to the dock using either #12 extra-hard usage type SO cord, or liquid-tight flex with indivdual conductors inside. Everything needs to be designed for wet locations.

Very good information. I appreciate all the great responses. I think I am ready to proceed with the project. Thank you very much.