HVAC Glossary

Gas furnace efficiency - 95% AFUE means only 5% of fuel is wasted up the flue.

How much heat you get for your electricity dollar. COP 3 = 3x more efficient than a space heater.

How well your AC performs on the hottest days. Less important than SEER2 for overall costs.

Old heat pump heating efficiency - higher = cheaper winter heating.

Heat pump heating efficiency rating - higher number means cheaper winter heating.

Old cooling efficiency rating - higher number = lower electric bills.

Cooling efficiency rating - higher number means lower electric bills. The current standard.

The indoor unit that moves air through your home. Contains the blower fan and, for heat pumps, the indoor coil.

Standard heat pump that extracts heat from outdoor air - the most common type.

Backup heating that kicks in when heat pump can't keep up - can be electric strips OR gas furnace.

Heat pump designed for extreme cold - works efficiently down to -15°F.

The outdoor unit of your AC or heat pump. Contains the compressor that does the heavy lifting.

A 90%+ AFUE furnace that extracts extra heat by condensing exhaust gases. Requires drain line for condensate.

When your heat pump briefly reverses to melt ice off the outdoor unit. Normal in winter.

Heat pump + gas furnace that automatically switches to whichever is cheaper to run.

Traditional central heating/cooling that uses ductwork to distribute air throughout the home.

Heating/cooling without ductwork - typically mini-splits with wall-mounted indoor units.

Compressor that adjusts speed to match demand - runs quieter and uses 20-50% less energy.

Split system with compact outdoor unit. Can be ductless (wall units) OR ducted (regular air handlers). 'Mini' refers to the outdoor unit size.

The most advanced stage control - adjusts output continuously from 10% to 100%. Maximum comfort and efficiency.

Outdoor unit with the fan on the side instead of the top. Becoming standard in 2025+ equipment.

Basic on/off operation - runs at 100% or not at all. The most common and least expensive option.

Any system with separate indoor and outdoor units connected by refrigerant lines. Includes both central AC and mini-splits.

Has high and low settings - starts on low, switches to high if setpoint isn't reached.

Furnace fan that adjusts airflow for quieter operation and better comfort.

Dividing your home into independent temperature zones. Heat or cool only the rooms you're using.

The temperature where your heat pump needs help from backup heating.

Unit measuring heating/cooling power. Higher BTU = more powerful system.

Calculation that determines the right size system for your home. Wrong size = comfort problems and wasted money.

When your system turns on and off too frequently - usually a sign of oversizing. Variable-speed systems don't short cycle.

The temperature where your thermostat switches from heat pump to backup heating to save money.

Unit of HVAC size. Most homes need 2-5 tons depending on square footage.

HVAC equipment works harder at altitude. Denver systems need to be sized ~20% larger than sea level.

Former federal tax credit for heat pumps - ended December 2025. No longer available.

Federal tax credit for EV charger installation - 30% of cost, up to $1,000. Expires June 30, 2026.

Income limit for HEAR rebates. Based on your household size and county - use the calculator to check.

Colorado's policy requiring utilities to cut emissions. The reason Xcel heat pump rebates tripled in 2025.

Colorado's income-based rebate - up to $8,000 for heat pumps if you qualify.

Colorado's largest electric and gas utility. Offers the biggest HVAC rebates in the state.

Alternative refrigerant common in Asia and Europe. Not ideal for cold climates like Colorado.

The refrigerant in most existing AC/heat pump systems. Being phased out but your system will still be serviced.

The new standard refrigerant - 78% lower environmental impact than R-410A.