Furnace AFUE ratings, federal minimums and the 2028 efficiency rule

A furnace's AFUE rating tells you how much of the heat in its fuel ends up heating your home. This guide explains what AFUE means and the federal minimum for each furnace type. It also covers the 95% AFUE rule from the U.S. Department of Energy (DOE) for gas furnaces made on or after December 18, 2028, and where it stands as of October 2026. You will also find ENERGY STAR's Version 5.0 furnace criteria, plus carbon monoxide safety and maintenance advice.

What AFUE means on a furnace

AFUE stands for annual fuel utilization efficiency. ENERGY STAR's furnace criteria page puts it this way: "In general, the percentage of the heat in the incoming fuel which is converted to space heat instead of being lost."

The federal definition is more technical. It calls AFUE "the efficiency descriptor for furnaces and boilers," determined using federal test procedures. The definition assumes weatherized furnaces sit outdoors. It assumes non-weatherized furnaces sit indoors, with all combustion and ventilation air brought in from outdoors. As the table below shows, federal minimums are set separately for weatherized and non-weatherized furnaces.

Federal minimum AFUE for new furnaces

Under 10 CFR 430.32, a non-weatherized gas furnace must have an AFUE of at least 80.0%. This applies to furnaces made on or after November 19, 2015, but before December 18, 2028. This class does not include mobile home furnaces. The rule lists separate minimums for other furnace types, including oil-fired and electric furnaces.

The 95% AFUE rule for gas furnaces made on or after December 18, 2028

The federal rule already lists a higher level for later gas furnaces. It says the AFUE for non-weatherized gas furnaces and mobile home gas furnaces "manufactured on and after December 18, 2028" shall be at least 95.0%.

That level comes from DOE's December 18, 2023 final rule, which says compliance "is required on and after December 18, 2028." In an April 27, 2026 notice, DOE said the 95% levels "effectively require the use of condensing technology."

Where the 95% rule stands as of October 2026

The 2026 developments below involve this rule. None of them has changed the federal regulation text. As of October 1, 2026, the eCFR still lists the 95.0% level for gas furnaces made on or after December 18, 2028.

The delay petition. On February 19, 2026, DOE received a petition from the American Gas Association, the American Public Gas Association and the National Propane Gas Association. The petition asked DOE to amend the compliance dates in two final rules. One rule covers consumer furnaces, and the other covers commercial water heating equipment. In its April 27, 2026 notice, DOE asked for comment on whether it should grant the petition and start a rulemaking. As of October 2026, we found no Federal Register action that granted the petition or changed the date.

The court case. The case is American Gas Association v. Department of Energy, No. 25-879. In a June 8, 2026 order, the Supreme Court granted the petition for a writ of certiorari and vacated the judgment. It remanded the case to the U.S. Court of Appeals for the D.C. Circuit "for further consideration in light of the position asserted by the Solicitor General in his brief for the United States filed on April 28, 2026."

We did not review the Solicitor General's brief or the D.C. Circuit docket after the remand. So we cannot say what has happened there since June 8, 2026. If you plan to buy a gas furnace close to the 2028 date, check the rule's current status first.

DOE's June 30, 2026 docket notice. DOE filed a notice dated June 30, 2026 in the rulemaking docket for the 2023 final rule. The docket number is EERE-2014-BT-STD-0031. In it, DOE wrote, "DOE is currently reconsidering the energy conservation standards for commercial water heaters and residential furnaces." It added, "DOE anticipates publishing a proposed rule this fall." As of October 2026, we found no such proposed rule in the Federal Register.

Date	Event
December 18, 2023	DOE publishes the final rule setting 95% AFUE for non-weatherized and mobile home gas furnaces
February 19, 2026	DOE receives the AGA, APGA and NPGA petition to amend the compliance dates
April 27, 2026	DOE publishes a notice asking for comment on the petition
April 28, 2026	The Solicitor General's brief for the United States is filed
June 8, 2026	The Supreme Court vacates the judgment and remands the case to the D.C. Circuit
June 30, 2026	DOE writes in a docket notice that it is "currently reconsidering the energy conservation standards" for commercial water heaters and residential furnaces
October 1, 2026	The eCFR, current as of this date, still lists the 95.0% level
December 18, 2028	Compliance date in the 2023 final rule

ENERGY STAR furnace criteria (Version 5.0)

The ENERGY STAR Version 5.0 furnace specification took effect on July 31, 2026. For gas furnaces, its requirements table sets an AFUE of at least 97.0% in the U.S. North and Canada. In the U.S. South, the table sets at least 95.0%. Oil furnaces need at least 87.0% across the U.S. and Canada. The table also lists an air leakage limit of 2.0% or less.

The specification says, "Weatherized furnaces are not eligible for ENERGY STAR." ENERGY STAR's criteria page lists which states count as the U.S. North. They include Washington, Ohio, Michigan, Minnesota, Colorado and Pennsylvania.

Furnaces and carbon monoxide safety

The U.S. Environmental Protection Agency (EPA) says on its carbon monoxide page, "Carbon monoxide is an odorless, colorless and toxic gas." Because it is impossible to see, taste or smell, EPA says CO "can kill you before you are aware it is in your home."

Furnaces show up more than once on EPA's list of CO sources. The sources EPA lists include:

• leaking chimneys and furnaces
• back-drafting from furnaces, gas water heaters, wood stoves and fireplaces
• worn or poorly adjusted and maintained combustion devices, such as boilers and furnaces
• a flue that is improperly sized, blocked, disconnected or leaking

The same EPA page passes along advice from the U.S. Consumer Product Safety Commission (CPSC). It says CPSC "recommends that every home have carbon monoxide (CO) alarms on each level outside each sleeping area." CPSC also urges a yearly professional inspection of all fuel-burning appliances. These include furnaces, stoves, fireplaces, clothes dryers, water heaters and space heaters.

Furnace maintenance

EPA's advice is to "have a trained professional inspect, clean and tune-up central heating system (furnaces, flues and chimneys) annually."

ENERGY STAR's maintenance checklist says a heating check should cover all gas or oil connections, gas pressure, burner combustion and the heat exchanger. It warns that gas or oil connections that do not operate properly are a fire hazard and can contribute to health problems. A dirty burner or cracked heat exchanger causes improper burner operation. Either one can make the equipment run less safely and efficiently.

The checklist also says to inspect, clean or change air filters once a month in your furnace, central air conditioner or heat pump. It says a dirty filter can raise energy costs. It can also damage your equipment and lead to early failure. Our guide to MERV ratings explains filter ratings and other filter-change advice.

If you are weighing a heat pump against a new gas furnace, see our guide to choosing a heat pump or gas furnace in western Washington.