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I have 2 buildings I'm wanting to supply power to strictly as a service and not adding the service from another source. The first building is more like a tiny home wanting to install 14 outlets, 4 lights with switches, be able to run refrigerator, microwave, air fryer, toaster oven, and electric heater and window air conditioner when needed. The other building I'd like to have 8 outlets (which will power things like a heat press, sewing machine, or other such equipment), 2 lights with switches, and be able to power window air conditioner or electric heater. What size breaker boxes do I need on my service pole and in each building if both buildings need one?

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    Install larger boxes than you currently need. Someone always wants to add outlets or lights you didn't anticipate.
    – keshlam
    Mar 14 at 14:57
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    Step 1: Talk to your local utility. Find out what standard service is. Most likely this is residential service ("home", tiny or not, plus a workshop). If they give you options of 200A and something above 200A, 200A will be fine. If they give options that start below 200A then we need to first discuss some more details. Report back what the utility says - or if you already have service on the pole, report what that service is and what equipment is already there). One other key question: how far from from pole to each building? Mar 14 at 15:08
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    Consider deleting "window air conditioner and heater" and replacing both with "mini-split heat pump" of a suitable operating temperature range for your climate. You'll spend far less on heating and the A/C will be quieter and more efficient as well.
    – Ecnerwal
    Mar 14 at 15:50
  • Yeah, or at the very least a window or through the wall mounted heat pump (such things exist!). Also, is there electric service to the property already, and how many square feet of finished space will each building be? Mar 15 at 2:00

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The answer to your question is not that hard. It can be found in the NEC Article 230.79. Part (C) States that if it is a one family dwelling it needs a service rating of not less than 100A. Part (D) says for any other installations you will need a service rating of not less than 60A. You need to check with your local AHJ and find out if they are going to require one of you buildings to be a one family dwelling. The other option you have is to feed the less used building from the the first building. At that point you will have to do a load study to see if everything will fit under the code minimums. Good luck.

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