If you have a home built since 1985 or so, you probably a home that is reasonably energy efficient. For older homes, if you've had an energy auditor evaluate your home, you probably have a list of recommendations for conservation measures you can take. The following tips may be useful.
Start with insulation. Every region of the US has different a different climate ranging from the incredibly hot desert Southwest with summer temperatures hovering around 115 degrees to frigid winter temperatures in Buffalo that dip into the minus teens. Regardless of where you live, insulation is going to keep the indoor temperatures where you want them for less cost.
Older homes especially have less insulation than new and frequently have no insulation at all. Find out what the local recommended R values are for ceiling, wall, and floor insulation. Your power company may have recommended values for energy conservation. And don't hesitate to ask if they have incentives or rebates.
Insulate from the top down. Put recommended insulation in the attic or ceilings first, then the walls, and finally under the floors or in crawl spaces.
Once the ceilings, walls, and floors are insulated, check the ducts. If ducts use the newer flexible ducting then you may not need to insulate, because the flexible ducting is insulated to R7 at the factory. If your ducts are metal, insulation to R-8 is recommended. A licensed contractor can seal leaks.
Insulation costs vary by region and local codes, but the range is typically from $2-3 a square foot.
Inexpensive latex builder's caulk should be used to caulk gaps and joints. For floor vents, caulk the joints between the metal boot and the wood floor to prevent heat loss. Run a bead of caulk around doors and windows where the window frame meets the framing. Also caulk the the joint between the baseboard and the floor; you can remove the quarter-round shoe molding, run your bead of caulk, then replace the molding for a nice clean finish.
If you have canister lights, remove the rim and caulk the gap between the can and the cut-out. Replace the rim and you're done.
Caulk and a caulk gun are inexpensive and readily available. You can easily caulk all your windows in a weekend for less than $50.
You can add foam gaskets to electrical outlets on exterior walls to cut heat loss.
Upgrading a furnace is a major expense, but one that can save a lot of money and energy. The best choice for your home is subject to many variables, but generally a forced air gas furnace is considered to be the most efficient because there is less wasted energy. Heat pumps, especially new models with with EnergyStar ratings, are almost if not equally efficient. Electric furnaces are typically the most inefficient because of inherent energy conversion and subsequent loss.
Upgrading windows can save energy costs too. Get leads for qualified installers from NextStep Remodeling .