The right home improvements could help shave energy bills by up to 35% or unlock up to $627 in annual savings, according to the U.S. Department of Energy.

Steve Chalk, who recently retired from his work at the department, told CNBC that a home energy assessment can help determine what the best savings projects are for a homeowner to take on.

Home energy audits cost about $400, but the price greatly depends on the type of residence and its location.

“You could easily have payback for that [assessment] in a couple of years,” Chalk says. “You’re not only saving money in the long term, but your house is more comfortable, and your air quality can be better.”

Some of the big items that are sending energy costs higher in many homes: proper insulation, incandescent lighting, or air conditioners that aren’t the correct size.

Chalk says one of the most common mistakes he sees is that many homeowners have an air conditioning system that is too large. Therefore, it does not run as long as smaller ones, Chalk says. “[That] might sound energy-efficient, but it’s not,” he says.

Sealing up air leaks in heating and air conditioning ducts or crawl spaces can also offer energy savings, Chalk says.

Even small changes can add up, too. For example, switching from incandescent lighting to LEDs can increase a home energy efficiency by about 85% alone, he says. Programmable thermostats and power strips can also help save on bills.

Some cities offer incentives to help offset energy efficiency and renewable energy upgrades. Check the Database of State Incentives for Renewables & Efficiency website to search for incentives by state.