A DOE rule would require all new gas furnaces to hit 95% AFUE starting December 2028 — but the rule is tied up in court, not settled law. Here's the real status and what your two paths forward look like.
In 2024, the Department of Energy finalized a rule raising the minimum efficiency for new gas furnaces from 80% AFUE to 95% AFUE, for units manufactured on or after December 18, 2028. An 80%-AFUE furnace vents combustion gas while it's still hot, straight out a metal flue. A 95%+ furnace has to be a condensing furnace — one that extracts enough extra heat from the exhaust that the leftover gas condenses into water, which means a completely different venting system (PVC pipe instead of metal flue, plus a condensate drain) and, in some homes, a heavier electrical or gas-line change to support it. That's a materially different, more expensive installation than a like-for-like 80% furnace swap — which is exactly the "huge inflation in install cost" concern homeowners and contractors have raised about this rule.
This rule is genuinely in legal limbo as of late 2026. Industry groups sued, and in mid-2026 the Supreme Court sent the case back down to the D.C. Circuit Court of Appeals for further review, agreeing with the federal government's own position that the case needed more consideration. The core legal question — whether a furnace's venting design counts as a protected "performance characteristic" DOE isn't allowed to regulate away — is still unresolved. The rule remains on the books with its December 2028 date, but it is not currently being enforced, and the Trump administration's own DOJ has signaled it's considering rewriting the rule. Treat "2028" as what's currently written down, not as a locked-in date.
Whether or not this rule survives its current legal fight, it's a reasonable thing to raise with a contractor today if your existing furnace is old enough that a replacement decision could realistically land after any final effective date: ask directly whether they'd recommend getting ahead of it with a condensing furnace or heat pump now, versus doing a standard like-for-like replacement and dealing with the rule later if it survives. A contractor who can talk through both paths, and isn't just steering you toward whichever pays them more, is worth more than one who has a single canned answer.
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