Here are some inexpensive ways to save energy and money:
Replace incandescent bulbs with compact fluorescent lights (CFLs) or light-emitting diodes (LEDs).
Install timers or occupancy sensors on fans and lights.
Plug electronics into smart power strips.
Install solar screens on west- and south-facing windows in hot climates.
Caulk and weather-strip doors and windows.
If you have a modest budget, here are some more possibilities:
Paint dark rooms a lighter color to use less electric light.
Replace older appliances and electronics with ENERGY STAR-rated models.
Install a high-quality furnace filter—but make sure your furnace can handle the extra pressure the filter will create. If it can’t, the new filter may restrict the airflow, reducing the efficiency and effectiveness of the system.
Install storm windows.
Seal heating and cooling ducts.
Replace plumbing fixtures with high-efficiency models (toilets, showerheads, faucets); rebates are available in many areas.
Insulate hot-water pipes.
Install a demand hot-water pump if you have to wait a long time for hot water.