The most energy efficient HVAC system depends on your specific needs and budget. Generally, high-efficiency systems that include features like variable-speed blowers, two-stage compressors, and advanced filtration systems will be the most energy efficient. Heat pumps are among the most energy-efficient HVAC options available. Additionally, installing a programmable thermostat can help you save on energy costs as well. Investing in a system with the ENERGY STAR® label is also important for optimal efficiency.