I need to get 45 amp service to my RV which is 230 feet from a 50 amp well pump sub panel. What is the least expensive awg copper wire I should use?

To deliver 240 volts with a 45 amp load 230 feet and keep voltage drop at 3% or less would require #4 copper wire.

To keep costs down, compare price of #4 copper to # 2 aluminum.

Thanks so much... just what I needed.

TK,

Please educate me. Why did you use 3% as opposed to the 5% end to end for your calc?

I use 3% for feeders and 2% for branch circuits.

I will consider this a feeder.

Recommended maximum vD is 5% total, in designing, you can use either 3% or 2% for either feeder or branch circuit.

My design, my choice.

TK,

I'm not disputing you. I agree that the cable would be a feeder. I also like your logic.

You do not have a problem with me. For example, I just learned that using the 5% figure for the feeder does not leave any room for the branch circuit side.

Thanks

What worries me is that he is pulling power from a (most likely) 240V circuit to feed an (almost certainly) 120/240V circuit.

Is there a neutral at the well house?

What worries me is that he is pulling power from a (most likely) 240V circuit to feed an (almost certainly) 120/240V circuit.

Is there a neutral at the well house?

I can go from the well house sub panel or directly from the main 200 amp panel at the meter (which has only the well house on it) they're about the same distance and thy both have neutral. My RV was plugged in at the well house but I had to move it. It needs the 45 amps because it has 2 air conditioners. Would you still recommend #4 copper or #2 aluminum going to the 200 amp panel as well (still 200-225 ft)?