What is the most cost-effective energy improvement?

Air sealing and attic insulation consistently deliver the best return on investment. Sealing air leaks around windows, doors, pipes, and attic penetrations costs little and can reduce heating and cooling costs by 10 to 20 percent. Adding attic insulation to the recommended R-value for your climate is also inexpensive relative to the savings. Smart thermostats and LED lighting pay for themselves quickly. A home energy audit with a blower door test pinpoints the most cost-effective improvements specific to your home.