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How can I run an electrical service 1000 feet to my cabin? I only need 100 amps. It seems like no matter what size wire I use, the voltage drop is very high. Any suggestions on wire size and how to best do this?

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  • 1 transformers, 2 figure out how much you really need - highly dependent on hvac, cooking
    – manassehkatz-Moving 2 Codidact
    Commented Sep 4 at 23:27
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    Also consider aluminum wire, perfect for feeders, and rather less expensive than copper, even in huge gauges that allow for small voltage drop.
    – Triplefault
    Commented Sep 4 at 23:56
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    Search the many answers here to the same problem, for example: diy.stackexchange.com/a/95227/79373
    – MTA
    Commented Sep 5 at 1:30
  • you need a high voltage transformer, probaly 600 volt or more
    – Traveler
    Commented Sep 5 at 1:38
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    Who is your utility? Is there a reason they can't get primary closer to your house?
    – ThreePhaseEel
    Commented Sep 5 at 3:57

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My neighbor buried 1500' of 2" pvc for the utility to pull primary 7.2kv to a pad mount transformer 25" from the house. He had to buy and bury the conduit and the vault pad. Utility supplied wire and transformer.

The utility first asked for 2.5", which he successfully argued down to 2" which was half the price of 2.5". The primary wire is small, carries under 7 amps @ 7.2kv to supply 200A at 240v. At 7.2kv there is effectively no voltage drop.

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    Another option could be overhead primary like I have. I'm 400 feet from primary over alfalfa to pole mounted transformer. This was done before I bought and have no idea about logistics. You would probably need a couple poles.
    – NoSparksPlease
    Commented Sep 5 at 3:46
  • I would want to check on the price of the poles first. Some prices are scary just for one pole.
    – crip659
    Commented Sep 5 at 11:02
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It seems like no matter what size wire I use the voltage drop is very high.

That's not how voltage drop calculations work. You don't pick the next larger size then do the calculation, get a bad number and do it again. You provide the calculator your data e.g. 1000', 80A worst case normal load and 5% voltage drop tolerable, and it spits out what size of wire you need. Vitally, you switch the calculator to aluminum wire, because running copper this large isn't even stupid.

Also, the US is a 240V country, so be entering 240V not 110V.

In that example I got 400 kcmil at 4.70%, or 500 kcmil at 4.01%.

Since you are talking about $7000 in wire alone, and probably that again for trenching, I would evaluate off-grid solar/battery.

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