Do you have any history on the house in terms of was it once possible a assisted living dwelling, how many bathrooms are in this dwelling and what is the total square footage of this dwelling.
Did you notice anything different about the laundry area in this dwelling.....As greg stated also did you notice anything in regards to aux. systems that you just can't answer.....sometimes people do a walk around and notice things they just cant explain.
Is it possible this was a boarding house at one time....can you contact the previous owners or possible check building permit records to see the classification of this dwelling at the time of the service installation to help answer this question.
In some areas it is common to see a standard meter socket and an additional one for a water heater and so on..and possible some additional meters if an assisted living home as well but very rare to see it located inside like this is........
I know you do not pull covers as HI's and I do not condone it on the Aux. Gutter...but as an electrician I would have to pull that cover to see if these meters are simply low voltage fed or normal......this I am sure would be a move Greg would like to make as well...
Any additional information you can provide regarding those questions will help narrow it down, you may have to do some investigative work on the dwellings original intent.