This really surprised me so I had a look at Denmark. I found plenty of listings which mention nothing about extra charges, and then I found one which said ''on departure you will pay DKK 50 per day for electricity/firewood/water.'' Another said ''pay your consumption'' on departure, so I can only assume the metre is read for every guest. This is in breach of Air rules as far as I understand, since no cash should be exchanged and how else will guest pay on departure? I looked at maybe 10 listings without extra fees and two with.
There is nowhere you can put it in the listing in the correct Air way since Air does not have an option for utilities fees. Yet, it seems that Denmark operates in a different way and simply sticks it in the house rules section. In one way, it isn't a bad idea for longer stayers to have the option to pay utilities since the host doesn't have to be upset about high consumption should guests choose to overuse, but you should not do cash exchanges with Air.
I think you should just set the price, most guests fall in a normal consumption pattern and it should not be an issue. Obviously the 50 per day host had that down as an average and was happy with that, so why could that not be part of the price? Seems like hidden fees to me.