The U.S. government offers the Residential Energy Efficiency Tax Credit, which is designed to cover 30 percent of the cost of your new HVAC equipment and the installation costs for up to $1,500. Geothermal heat pumps are also eligible for a 30 percent tax credit without the $1,500 limit.

This program requires that you purchase high-efficiency HVAC equipment. Split system air conditioners and heat pumps must have a Seasonal Energy Efficiency Ratio (SEER) rating of 16 or higher and packaged system A/Cs must be rated SEER 14 or higher. The requirements for geothermal heat pumps are slightly more involved, so you should check them out on the program's website.

In the end, you should purchase the most efficient system you can afford because it will be the most cost-effective investment you can make. It will save you a lot of money on your utility bills for years to come. If you would like to get advice from an expert in person, consider having an energy audit. The auditor will be able to figure out which system would work best in your home and find other ways for you to save money on your utility bills.