If you have never had one. I highly recommend you get one. My local energy co. does them for free if you live in a certain zip code. I had mine done yesterday. I found out I am heating the hallway by a diverted heat run (the reason my bathroom has no heat). I also heat the laundry room with a tapped flex pipe off of my kitchen run. I supply electricity to my downstairs neighbor off an extension cord plugged into a outlet off my furnace?? He apparently runs his TV, stereo, computer, and a space heater off it?? When I unplugged it he came down and asked me if I could wait until the end of the bears game?? I expect some serious savings next month. People suck...