Heating & Cooling
Heating and cooling
What a system's age, fuel, and ratings mean for a repair-or-replace decision, and what to ask before anyone opens the equipment.
10 answers
- 80% vs 95% AFUE Furnace: What the Efficiency Rating Means AFUE is the share of fuel a furnace turns into heat. The federal floor is 80% for most gas furnaces; the 95% rule for 2028 is back under review.
- AC Not Working in a Heat Wave: How to Stay Safe Until Repair Get people at higher risk somewhere air-conditioned first; fans will not prevent heat illness in extreme heat. How to tell a failed AC from an overwhelmed one.
- Do Heat Pumps Work in Cold Weather? What to Check Before Buying Yes, with limits: output falls as it gets colder. How ENERGY STAR defines a cold-climate heat pump, what backup heat does, and what to ask a contractor.
- Do You Need a Permit to Replace a Furnace or Air Conditioner? Usually, yes. The model code requires a permit to replace gas and mechanical equipment; the exemptions are narrow, such as portable units and minor parts.
- How to Compare HVAC Quotes and When to Get a Second Opinion Two quotes are comparable only if they name the same equipment, sizing basis and scope. What a written proposal should list, and what to verify first.
- Is R-410A Being Phased Out? What the 2026 EPA Rule Changed Existing R-410A systems can still be repaired and recharged. Since July 27, 2026, pre-2025 R-410A equipment can be installed again, but some states differ.
- No Heat in Winter: How to Stay Safe Until the Furnace Is Fixed Keep generators and grills outside, never heat with a gas oven, keep space heaters 3 feet from anything that burns, and protect pipes while you wait.
- SEER2 Requirements by State: What a New AC Must Meet Since January 1, 2023, new central air conditioners must meet SEER2 minimums that differ in the North, Southeast and Southwest. The numbers, and how to check.
- What Size AC Do I Need? How a Load Calculation Answers It The right size comes from a Manual J load calculation for your house, not from square footage. What the code requires and how much oversizing is allowed.
- What to Do When Your Carbon Monoxide Alarm Goes Off Four loud beeps mean get everyone outside and call 911 from fresh air. A chirp is usually a low battery or an alarm at the end of its life.
How US homes are heated
Main heating fuel, share of 129.2 million occupied homes
- Utility gas 46.5%
- Electricity 41.3%
- Propane or other tank gas 4.9%
- Fuel oil or kerosene 3.9%
- Wood 1.4%
- No fuel used 1.2%
- Other fuel 0.5%
- Solar energy 0.3%
- Coal or coke 0.1%
Utility gas and electricity are the main heating fuels in nearly nine in ten occupied homes in the United States. The fuel a house heats with shapes much of what applies to it, from equipment options to safety checks. The chart above shows the national split from the Census Bureau’s American Community Survey.