If you’ve heard something about a new furnace law in Colorado and aren’t sure what it actually means for your home, you’re not alone. There’s been a lot of talk about a January 1, 2026 “deadline,” and it has left plenty of homeowners across Berthoud, Longmont, and the rest of Northern Colorado wondering if they need to act right away.
Here’s the short version: you don’t. The new rules apply to new furnace installations, not to the system already running in your home.
IMS Heating & Air has been part of this community since 1999, and we want our neighbors to have the straight facts instead of the rumors. Below, we’ll walk through what the law actually says, what it means when the time comes to replace your furnace, and how to plan for it without the stress.
What Is HB23-1161?
HB23-1161 is a Colorado law passed in 2023 that sets new emissions and efficiency standards for gas furnaces. As of January 1, 2026, it requires that new furnace installations meet one of two standards. The law applies to manufacturers, distributors, and contractors installing new equipment. It does not apply retroactively to furnaces already installed in Colorado homes.
What Is Ultra-Low NOx and ENERGY STAR?
The law gives installers two separate paths to compliance, and a new furnace only has to meet one of them.
Ultra-Low NOx (ULN) refers to a limit on nitrogen oxide emissions released when fuel is burned at high heat. A compliant furnace can’t exceed 14 ng/J of NOx emissions.
ENERGY STAR is a U.S. EPA and DOE program that recognizes high-efficiency equipment. Colorado falls in the ENERGY STAR North region, where the minimum AFUE rating is 95% through July 30, 2026, rising to 97% AFUE starting July 31, 2026.
These are two different routes to the same goal. A new installation doesn’t need to check both boxes, just one.
What Does This Mean for You as a Homeowner?
For most homeowners, the practical impact is smaller than the headlines suggest:
• Your existing furnace is not affected. There’s no penalty, fine, or fee tied to owning an older system.
• Gas furnaces are not banned. Compliant models are available and are being installed across Colorado right now.
• When you do eventually replace your furnace, whether that’s a planned upgrade or an emergency swap, the options on the table will be ones that meet the ENERGY STAR or ULN standard.
• Working with an installer who understands the current requirements makes that process a lot smoother.
In other words, this is a change to what’s available when you buy new equipment, not a mandate on what you’re required to do with what you already have.
