We are currently building an addition to our house. It was a duplex before (one part stick built, other part mobile home, they were connected by a common entryway). We moved the mobile home away and are building a stick built addition that will also have a 'mother-in-law suite'. Before, we had two separate meters for each duplex half. We would like to keep this setup with the new addition.

I have been told by an electrician that this was against code. He said he talked to the electrical inspector as well and he stated we could only do that if we had a fire wall between the two units.

I have been doing some reading and my understanding of the code does not reflect this. We have one service to the building (transformer from the electrical utility) that just happens to be connected to 2 meters. So while we can have only one 'service', we can have multiple 'service entrances', no?

So the question is can we have 2 meters for one structure that had 2 units in it? We have to follow 2017 NEC. This is in Minnesota, Blue Earth County. The utility is a local cooperative. The County does not impose or inspect anything here, the only aspect they consider for building permits is zoning and setback compliance, so they do not have a building code. Electrical is inspected by the State of Minnesota.

This is what we currently have (third meter is for an outbuilding on the property)

Current meter setup

  • 1
    I suggest adding the jurisdiction - state, city/county. This may vary quite a bit by jurisdiction and not be a strictly code question. Nov 18, 2018 at 15:23
  • This may even be a matter of utility rules -- who's your electric utility? Nov 18, 2018 at 15:43
  • @manassehkatz -- indeed -- the question of separate vs joint metering when ADUs (ancillary dwelling units, i.e. "in-law suites") are present is a difficult one as the model Codes do not seem to speak to this. Nov 18, 2018 at 15:44
  • Except for making sure that the circuits - including grounds - are kept separate, I don't see how this is a code issue. I can see reasons why jurisdictions and/or utilities might like or not like it. Nov 18, 2018 at 15:48
  • @manassehkatz -- the only verbiage in the NEC that touches on this is 210.25, but that asks the rather deep question of "is an ADU a 'dwelling unit' in the Code sense of the term?" Nov 18, 2018 at 15:52

1 Answer 1


I'll take a crack at this but the NEC article that would deal with this is 230, Services, which I don't find very clear. It goes without saying that unless you're prepared to literally fight city hall, the inspector's interpretation is all that really matters.

If you look at the NEC definition of a Building in Article 100:

Building. A structure that stands alone or that is cut off from adjoining structures by fire walls with all openings therein protected by approved fire doors.

Note that adjoining structures are considered separate buildings only if they are separated by fire walls. I guess they are considering the new setup to be adjoining structures.

Looking at the photo, I would think each of those meter pans are fed by underground service laterals to the same utility transformer.

Now look at

230.2 Number of Services. A building or other structure served shall be supplied by only one service unless permitted in 230.2(A) through (D).

(The exceptions (A) through (D) are stuff that probably wouldn't apply.)

You could conclude that three services - three sets of wires serving three separate meters and main disconnects - require that the three spaces be separate buildings; and per the definiton above, these adjacent spaces are all one building unless they are separate by a fire wall.

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    I'm wondering if he could get his utility to consolidate things into a single, beefier lateral that feeds all three meters via a trough... Nov 19, 2018 at 2:02
  • Thanks! Not sure if it matters, but the transformer from the utility is right next to the meters, just not in the picture. It is on our property, and only serves those 3 meters. The transformer was put in only a few years ago, before it was above ground wires, but also 3 meters. Nov 19, 2018 at 2:08
  • That's good news if you have to set this up differently - a single lateral feeding a trough or a three meter pack would definitely be compliant but you will need new service conductors and maybe a bigger pipe. Nov 19, 2018 at 3:51
  • 1
    I would certainly hope that you wouldn't have to literally fight city hall.
    – Vikki
    Dec 5, 2019 at 0:10

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