10/31/2025
Do you have an old furnace? You might want to think about getting it replaced before these requirements go into effect.
On the Horizon: Furnace Efficiency Requirements for 2026.
Starting January 1, 2026, all new natural gas furnaces sold in Colorado must be high-efficiency models with an Annual Fuel Utilization Efficiency (AFUE) of at least 95% and meet new ultra-low NOx emissions standards. This new requirement, set by Colorado's HB23-1161, replaces the previous 80% AFUE minimum. The change aims to reduce smog-forming nitrogen dioxide pollution and cut consumer energy bills.
Key requirements for new furnaces
Efficiency: A minimum AFUE of 95% is required.
Emissions: New furnaces must meet ultra-low NOx emissions standards.
Sale date: The mandate for new furnaces takes effect on January 1, 2026.
Current options (before 2026): Before the new law, 80% AFUE furnaces were the standard. The sale of standard 80% and 92% AFUE furnaces will be phased out by the end of 2025.
Why the change is happening
Environmental impact: The new standards are part of a larger effort to reduce the state's overall emissions and improve air quality.
Energy savings: Higher efficiency furnaces use less energy, which should lead to lower heating bills for consumers, especially in Colorado's colder climate.
What you need to know
For replacements: If your furnace needs replacement now, you can still purchase an 80% AFUE model, but you will have a limited time to do so.
Installation: The installation of new, higher-efficiency furnaces is required for all new gas furnaces sold in the state after the 2026 deadline.
Cost: Ultra-low NOx and high-efficiency furnaces typically have a higher upfront cost than older, less efficient models.
Installation challenges: In some older homes, retrofitting a high-efficiency furnace may require more complex and costly installation to accommodate the new smaller exhaust vent and condensate drainage requirements.
