Amateur question about branch circuit length

[GWBMCSE]

I have run my fair share of electrical DYI but my experience has been limited to new circuits in a house/shed/etc. I need some guidance on a run that's going to be about 250ft +-10ft.

I have a main detached garage that already has a 200A box ran from the transformer and I am building a new garage, about 250ft away, that needs power. I am wanting to run a 20A branch circuit from the first building to the second but I'm worried about voltage drop. All I will ever have in the new building is 4 led shop lights and a Liftmaster rollup door motor. I have no info on the lights but the motor specs show 120V @ 1.5A (From their website: 120V AC, 60Hz with a 1.5A current rating). I dont mind running 2 20A circuits through the underground conduit as it's recommended that garage door openers be on their own circuit.

What is confusing me is this:
1. A relative of mine, who is an electrician as his day job, told me I should be ok using 10/2 uf run underground through conduit. This makes me and my wallet happy BUT
2. The electrician that wired my new house says I should run a 100A sub box to new garage in case I ever wanted to plug in some tool or compressor...

I do not plan to do anything but park a couple of cars in the new garage so I wanted to get your opinions, especially whether or not 10/2 would be sufficient for that length of run.

Thanks

 

[Dennis Alwon]

Please try diychatroom.com

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