There's nothing more efficient, when paired with the 40MPHA indoor unit, this system has SEER rating at 42 with 15 HSPF, making it ENERGY STAR®certified. The new, ultra-efficient 38MPRA outdoor unit with built-in basepan heater offers year-round comfort. Its impressive cooling operating range maintains consistent capacity from -22° F to 122° F. On the other end of the spectrum, the systems high heating capability is exceptional, running 100% to -22° F to 86° F temperature range. No matter the temperature outside, this system can handle the extremes.