For 2026, MRCOOL delivers 24 SEER2 efficiency, while Zone Air offers 23 SEER2....

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For 2026, MRCOOL delivers 24 SEER2 efficiency, while Zone Air offers 23 SEER2. The choice comes down to your winter lows: choose MRCOOL for value when temperatures stay above -15°F, or Zone Air Hyper Heat for heating down to -22°F.