i will give you an opposing perspective and recommend you stay in the hotel. interviews are anxiety riddled as it is and controlling as many variables as possible that will minimize that anxiety will only make you perform better. if this were your home institution, i think that would be a different story, but it doesn't sound like it.
also, would you be staying at the one hotel that the other candidates will be staying at? the way you worded it it actually doesn't sound that way. when it comes to your interview experience it makes an enormous difference sticking with the candidates day in and day out vs. showing up and leaving on your own. but, if everyone is making hotel plans on their own, this becomes less significant. the little things in your interview day really do make a difference in your perception of the school - shuttle rides to and from the hotel, waiting around with candidates, etc. so definitely don't take them for granted.
"charging it to the school" is a little harsh in my opinion, programs budget for these sorts of things and expect some to use more than others - for instance you wouldn't be asking for a flight reimbursement, just a hotel. a strategically worded email to the program coordinator will make your situation seem just fine.