Effect: Your energy bills will still be higher than necessary if you don't start with cheaper, smaller upgrades to improve the energy efficiency of your home, such as caulking around windows and doors and adding insulation.

9. Upgrading to the most efficient furnace on the market

Cause: You want the sleekest, most energy-efficient furnace available because it will be the most cost effective as well.

Effect: You may end up replacing an oversized furnace with another (albeit more efficient) oversized furnace. The U.S. Department of Energy reports that most U.S. homes have oversized HVAC systems. Again, insulate and weatherize to maximize efficiency, then get the smallest system that will comfortably meet your heating needs, which will be substantially reduced. Also make sure it is professionally installed.

10. Using incandescent light bulbs for heating

Cause: Incandescent bulbs give off more heat than light, so they must be warming up the house.

Effect: It is hard to see this logic as anything but a weak excuse for holding on to the Edison bulbs rather than switching to CFL and LED lighting. In fact, one German entrepreneur is marketing incandescent bulbs as "heat balls" to skirt EU laws against the old-style bulbs. However, I doubt he is keeping cozy this winter simply by sleeping with the lights on.

Source: http://www.networx.com/article/10-mistakes-people-make-with-heat