HVAC and home repair terms, in plain English

Last checked October 29, 2026

Short answer

The words on an AC, furnace or plumbing quote, in plain English, with what each part costs in Las Vegas where we have it. Start with the big three: the compressor ($1,350 to $1,800 to replace here), the capacitor ($90 to $400), and the evaporator coil ($650 to $1,200).

AC and heat pumps

Split system: An AC with two parts: an outdoor unit (compressor and condenser coil) and an indoor unit (furnace or fan coil, which holds the evaporator coil and the fan). What's in a replacement quote
Package unit: An AC where everything is in one outdoor cabinet, often on the roof. Replacing a rooftop unit can mean paying for a crane. Split vs package diagram
Compressor: The pump in the outdoor unit that pressurizes the refrigerant and sends it to the condenser coil. It's the most expensive part to replace: $1,350 to $1,800 in published Las Vegas ranges. AC repair prices
Condenser coil: The coil in the outdoor unit that dumps your home's heat outside and turns the refrigerant back into a liquid. ENERGY STAR says to have it cleaned as part of a tune-up.
Evaporator coil: The cold coil inside, above the furnace or in the fan coil. Your home's air blows across it and comes out cool. A leaking one runs $650 to $1,200 in published Las Vegas ranges. AC repair prices
Refrigerant (Freon): The fluid that carries heat out of your house through copper lines. It doesn't get used up, so needing more means there's a leak. Older systems use R-22, which hasn't been made in the US since 2020. New systems use R-454B or R-32. The refrigerant switch
Capacitor: A small part that stores energy and gives the compressor and fan motors the jolt they need to start and keep running. Heat and direct sun wear them out faster. Usually $90 to $400 to replace here. AC repair prices
Condensate drain line: The pipe that carries water your AC pulls out of the air away from the indoor unit. If it clogs, water backs up and can damage the unit and your home, and the AC may shut off. ENERGY STAR says to check it during maintenance.
Air filter: The filter in your return vent or by the indoor unit. ENERGY STAR says to inspect, clean or change it once a month.
Ton: A unit of cooling, not weight. One ton is 12,000 BTU per hour. Las Vegas homes usually have 3 to 5 tons. Size and price your home
Manual J: The industry-standard load calculation from ACCA that sets the right AC size from your insulation, windows, air leaks and sun, not just square feet. Ask every contractor for one. AC sizing
SEER2, EER2 and HSPF2: Efficiency ratings. SEER2 is seasonal cooling efficiency, EER2 is efficiency at peak heat, and HSPF2 is heating efficiency for heat pumps. In Nevada, a new split heat pump must be at least 14.3 SEER2 and 7.5 HSPF2, and the Southwest has extra EER2 minimums for ACs. Nevada minimums
Heat pump: An AC that can also run in reverse to heat your home. The reversing valve is the part that switches directions, and it runs $400 to $700 to replace in Las Vegas. Heat pump prices
LRA (locked rotor amps): The surge of current your compressor pulls for a split second when it starts. It's on the outdoor unit's label, and it decides how many batteries you need to run the AC in an outage. Powerwall AC checker

Heating

AFUE: How much of the gas a furnace burns actually becomes heat in your home. A 95% furnace wastes about 5%. A federal rule requires new non-weatherized gas furnaces to be 95% AFUE starting December 18, 2028, though the gas industry has asked for a delay. Furnace prices and the 2028 rule
Heat exchanger: The metal chamber in a furnace that keeps combustion gases separate from the air you breathe. A cracked one can leak carbon monoxide, and most get replaced rather than repaired. Furnace repair prices
Igniter and flame sensor: Two small furnace parts that fail often. The igniter lights the burners, and the flame sensor confirms the flame is lit. Nationally, an igniter runs $150 to $250 and a flame sensor $75 to $250. Furnace repair prices
Heating and cooling degree days: A measure of how much heating or cooling a place needs. Las Vegas averages 1,836 heating degree days and 3,722 cooling degree days a year, so cooling demand is about twice heating.

Water and plumbing

Hard water and grains per gallon: Water with a lot of dissolved minerals. Las Vegas Valley Water District puts valley water at 280 ppm, or 16 grains per gallon, and says to set softeners to that number. Hard water and water heaters
PRV (pressure reducing valve): A valve where water enters your house that keeps pressure safe. LVVWD says sustained pressure over 80 psi can damage plumbing, and homeowners are responsible for a PRV when pressure is over 80 psi. Plumber prices
T&P relief valve: The safety valve on a water heater that opens if temperature or pressure gets too high. Under Southern Nevada code its drain has to go outside the house. Water heater code rules
Expansion tank: A small tank on the water heater line that absorbs pressure as water heats up. The City of Las Vegas requires one when a check valve or backflow device stops pressure from going back to the main. Water heater code rules
Slab leak: A leak in a pipe under your concrete foundation. It's fixed by breaking the slab to reach it, or by rerouting new pipe around it, which costs more. Nationally, repairs run $1,000 to $4,000. Slab leak prices and LVVWD help

Power and bills

Demand charge: A part of an electric bill based on your highest burst of use, not just your total. NV Energy's residential version is explained in our NV Energy guide. NV Energy explained

Common questions

What is the difference between a split system and a package unit?

A split system has an outdoor unit and an indoor unit. A package unit has everything in one outdoor cabinet, often on the roof.

What does an AC capacitor do?

It stores energy and gives the compressor and fan motors the boost they need to start and keep running. Heat and direct sun wear capacitors out faster.

What happens if my AC drain line clogs?

Water backs up and can damage the unit and your home, including mold, and the AC may shut off.

What does a ton mean for an AC?

One ton of cooling is 12,000 BTU per hour. It describes cooling capacity, not weight.

Sources

Show all 20 sources

Rules, rebates and prices change. If something here is out of date, tell us on the share page and we'll fix it.