If you’ve been keeping up with Colorado’s 2026 furnace regulations, you already know there’s a lot to track. Here’s a specific, practical update: the ENERGY STAR efficiency requirement for gas furnaces in Colorado just increased. This doesn’t change whether gas heating is available to you, and it doesn’t require you to replace a system you already own. Here’s exactly what changed and what it means if you’re in the market for a new furnace.
Quick Recap: What HB23-1161 Has Always Required
Colorado’s HB23-1161 took effect January 1, 2026, requiring new gas furnace installations to meet one of two efficiency paths: ENERGY STAR certification or Ultra-Low NOx compliance. Existing systems in your home aren’t affected either way. For the full picture on the law itself, see Colorado’s 2026 HVAC law.
What Changed on July 31, 2026
From January 1 through July 30, 2026, the ENERGY STAR efficiency threshold for Colorado’s North region was 95% AFUE (Annual Fuel Utilization Efficiency). As of July 31, 2026, that threshold increased to 97% AFUE. Any new gas furnace installed through the ENERGY STAR compliance path after this date must meet the higher standard.
The Ultra-Low NOx path is unaffected by this change. A furnace compliant under that standard must keep nitrogen oxide emissions at or below 14 ng/J, and installations only need to satisfy one of the two paths, not both.
In simple terms: before July 31, a 95% AFUE furnace could qualify under ENERGY STAR. After July 31, it needs to reach 97% AFUE, or qualify under Ultra-Low NOx instead.
What This Means for Homeowners Replacing a Furnace
If you’re shopping for a new furnace now, the pool of ENERGY STAR–qualifying models has shifted toward higher-efficiency equipment. That’s not a reason for concern. Compliant options exist across a range of prices and features, and the change affects which models qualify, not whether gas furnaces remain a viable choice.
The most useful thing you can do is work with an installer who understands the current requirements and can walk you through equipment that meets either path. If your existing furnace is still running well, none of this affects you directly. This update only applies to new installations going forward.
Frequently Asked Questions
Do I have to replace my furnace because of this change?
No. This update only applies to new furnace installations. If your current system is working, you’re not required to do anything.
Does this mean gas furnaces are being phased out in Colorado?
No. Compliant gas furnaces are still available and being installed. The change affects which specific models qualify under the ENERGY STAR path, not whether gas heating itself remains an option.
What if I already scheduled an installation before July 31?
Requirements are based on the installation date, not when you scheduled or ordered equipment. Check with your installer to confirm which standard applies to your specific timeline.
Is Ultra-Low NOx a better option than ENERGY STAR now that the AFUE requirement is higher?
Neither path is inherently better. Since a furnace only needs to meet one of the two standards, the right choice depends on the specific equipment available to you and your installer’s recommendation, not a fixed hierarchy between the two paths.
Where can I learn more about the original law?
See Colorado’s 2026 HVAC law for the full breakdown of HB23-1161 and what it means for existing systems.
Talk to a Local Haining Home Services Expert Today
Haining Home Services stays current on Colorado’s furnace standards so you don’t have to track every regulatory update yourself. Whether you’re planning ahead or dealing with a system that’s already failed, we can walk you through your options.
Call Haining Home Services at (970) 242-4429 or schedule online to talk through your furnace replacement options.
This post is intended as general information and is not legal advice. For questions specific to your situation, consult a licensed contractor or the relevant state agency.