Hot and Cold Tech Speak Confused by HVAC lingo? Believe it or not, it's meant to make understanding and buying the equipment easier. These terms allows you to compare apples to apples among units in the same fuel category. Knowing what the terms listed here mean will come in handy. SEER: The seasonal energy-efficiency ratio (SEER) rates how many Btu an air-conditioning unit will remove for each watt of electricity consumed. The higher the SEER, the less you spend on operating costs. Federal law mandates a minimum SEER of 10 for all new air-conditioning units. Tonnage: An air-conditioning ton equals 12,000 Btu per hour. That means a three-ton air conditioner can remove about 36,000 Btu of heat per hour from your home. AFUE: The annual fuel-utilization efficiency estimates how much heat a unit delivers for every dollar spent on fuel. The higher the AFUE, the lower your heating bills.