Hello,
I recently purchased a property which currently has electrical service running into a solitary shed. 400 feet away from the shed is an old foundation I would like to build a cottage on. I'm trying to figure out what it may cost me to run power underground from the shed to the proposed cottage.

The shed panel box was installed several years ago. I don't know if it's 100, or 200 Amp, but it powers a fridge, well pump, outdoor light, and a couple of receptacles. A trench could be easily dug between the shed and the foundation.

Using an online calculator I determined that I require 500 mmca aluminum wire to run the distance (120 volt, single phase, 400 ft, 100 Amp). Unfortunately, I know almost nothing about number of conductors, shielding, or running cables underground.

Does anyone know what wire/shielding would be suitable for this job, and what it might cost?

Get the power company to move the service closer to where you want to build. Although you can get wire which will handle the load, it won't fit the lugs on 100 or 200 amp CB panel... and it would be very expensive to purchase that wire.

Also, forget about a 120v feeder or service. This makes absolutely no sense.
Stick with a 120/240v feeder or service, for several reasons. Wires size and voltage drop being the main ones.

I was afraid of that answer, the cost of moving the service would likely negate the cost benefit of using the old foundation. Thanks for the helpful information.

I want to feed a 3phase 100 amp panel 120/208v which is 400 ft. Away. I then want to feed another panel (100amp 3 phase) from that first panel which will have a load of 60 amps. One of those loads is 200 ft away 3phase 30 amps. What wire sizes do I need to feed these panels and load.

I want to feed a 3phase 100 amp panel 120/208v which is 400 ft. Away. I then want to feed another panel (100amp 3 phase) from that first panel which will have a load of 60 amps. One of those loads is 200 ft away 3phase 30 amps. What wire sizes do I need to feed these panels and load.A) This should be in it's own thread. This has nothing to do with the original post.

B) Your electrician will know exactly how to do this. This is not a DIY project and anyone who has to come to a DIY message board to ask how should not be doing it!