I show a lot of REO properties and I can tell you it doesn't take a rocket scientist to figure out that the ones with heat on and electricity for lights get a lot more attention from buyers than those that are freezing with dark foreboding spaces. I carry a Mag light for the homes without electricity but my buyers usually won't even venture into the basement if they are shivering on the first floor.
How much can a monthly bill be to minimally heat a home to at least 65 degrees? In Colorado Springs the REO contractors I talk to all say that the banks will reimburse for the electric bills at closing- so why not turn on the heat and lights so buyers can at least peruse the home without fear of frostbite. Chances are the home will receive a contract during the winter months if warm and inviting instead of having to wait until spring to capture attention, so the cost of heating the place outweighs price decreases for days on market.
From my observations the average time a buyer will spend in a vacant property with no heat or lights is about 5 minutes and they won't even investigate all the rooms. By the time they hit the kitchen their noses are running, the cold has stimulated the need for a bathroom, and there is NO discussion about where to place the furniture. On the other hand a home that at least has lights and heat will capture their attention for about 15-20 minutes and sometimes longer if they are considering how to overcome some of the obvious defects and cosmetic pitfalls. That property will at least get on the short list. From my perspective there is really no benefit to turning off electricity in vacant properties if the seller is serious about closing during the winter season in Colorado.