lower floor of a house eh?
Well, here are some things that we did to help cut our electrical bill (most of which goes to heating)
You will have to accept the fact that you will have to spend money to save money. I know, it sucks because its not YOUR place, but you really dont have to spend all that much, and the savings offset the costs in the first month alone.
The number 1 enemy is drafts. Cold air coming into your place, our biggest culprit was the door. We got the landlord to reposition the weatherstripping on the door. Made a big difference. If your door has no weatherstripping ask them to put some in. If not, then ask if you can do it yourself, because it will save you money. There is still some air coming in the bottom of our door, so we just put a towel in front of it. Makes a big difference. Next, the windows... our apartments weren't that good. So, buy some of that window film stuff from a home depot lowes or whatever and put it on. Helps the windows loose less heat and cuts down on drafts. While you are doing that, feel with you hands around the outside frame of the window.... if you can feel any cold air flowing out of it, tell the landlord that you want them caulked. A 2 dollar tube of caulking will do wonders! Next, since its a house, check the plugs around the place, stick your face or hands up to them and see if you can feel any cold coming out of them. If so, get some foam gaskets (again, big DYI store) and they get installed behind the faceplates. They are really cheap and this will also prevent lots of cold air from coming in.
Turning down the termostat at night will help too, if there are separate ones for each room, leave br one where it is, and turn the other ones down to almost nothing, at least 20 degrees lower than they normally are for nite time, the place won't cool down all that much.
Since you are in a basement look for other places cold air might be coming in, conduits, pipes etc.... tell-tale signs are condensation. Any condensation means cold air is getting in.
ask if you have any questions