HVAC Terms Every Homeowner Should Know

Shopping for a new heating or cooling system can feel like reading a foreign language. Here’s a plain-English guide to the terms you’ll actually run into — so you can make a confident decision instead of nodding along.

Efficiency ratings

SEER2 measures how efficiently an air conditioner or heat pump cools over a season. Higher is more efficient — think of it like miles per gallon for your A/C. AFUE does the same for furnaces: a 95% AFUE furnace turns 95% of its fuel into heat. HSPF2 rates a heat pump’s heating efficiency.

Capacity and sizing

Tonnage describes a cooling system’s capacity — one “ton” equals 12,000 BTUs per hour. It has nothing to do with weight. BTU (British Thermal Unit) is the basic measure of heating or cooling energy. Bigger isn’t better: an oversized system cools or heats in short bursts, leaving your home humid or unevenly heated.

Air quality and airflow

MERV rates how much an air filter captures, from large dust down to fine particles. Higher MERV catches more, but too high for your system can restrict airflow — match the filter to your equipment. Static pressure is the resistance air meets moving through your ducts; high static pressure strains the blower.

Comfort and control

A variable-speed or two-stage system runs at lower output most of the time and ramps up only when needed — quieter, steadier, and better at removing the humidity our summers are known for. Zoning uses dampers and multiple thermostats to heat or cool different areas independently.

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