Andrew Martinez

Colorado’s New Low-NOx Furnace Law: What It Means for Homeowners, Energy Costs, and Your Next Heating System

Starting in 2026, homeowners across Colorado are seeing major changes in the heating and cooling industry due to new environmental regulations. If you’ve heard about the Low-NOx furnace mandate, you’re not alone.
 
Many homeowners are asking the same questions:
  • Is my furnace still legal?
  • Will replacement costs go up?
  • Are gas furnaces going away?
  • What does this mean for my energy bills?
 
This guide explains the new law in plain language—what it is, who created it, why it exists, and what it means for your home, comfort, and budget.
 

What Is the New Low-NOx Furnace Law in Colorado?

 
Colorado’s new furnace regulation comes from House Bill 23-1161, which was passed by the Colorado General Assembly and signed into law by Governor Jared Polis in June 2023.
 
The law requires that:
Beginning January 1, 2026, all newly sold or installed gas furnaces and water heaters in Colorado must meet ultra-low nitrogen oxide (NOx) emission standards.
 
This regulation applies specifically to:
  • Gas furnaces
  • Gas water heaters
  • Certain gas appliances
 
But it does not require homeowners to replace existing equipment.
 
Your current system can:
  • Continue operating
  • Be repaired
  • Be maintained
The law only applies when installing new equipment.
 

Why Did Colorado Implement This Law?

 
The primary goal of the new regulation is to improve air quality across the state, particularly along the Front Range.
Nitrogen oxides (NOx) are pollutants produced when fuel burns. These emissions contribute to:
  • Smog
  • Ground-level ozone
  • Respiratory health problems
 
Colorado has struggled with ozone pollution for years, and lawmakers introduced this legislation to reduce emissions from residential heating systems.
Industry organizations have also noted that the regulation is part of a broader effort to reduce emissions from natural gas appliances and gradually shift energy usage toward cleaner technologies over time.
 

Key Dates Every Homeowner Should Know

 
Understanding the timeline helps explain why this change is happening now.
2023: Law passed and signed into law
December 31, 2025: Manufacturing cutoff for non-compliant equipment
January 1, 2026: New emission standards officially took effect
 
These dates matter because equipment manufactured before the cutoff may still be installed while inventory lasts, but all newly manufactured equipment must comply with the new standards.
 

What Is a Low-NOx Furnace?

 
NOx stands for: Nitrogen Oxides
These gases are produced during combustion in gas-fired heating equipment. 
The new law requires furnaces to meet Ultra-Low NOx emission limits.
 
Specifically:
Less than 14 nanograms of NOx per joule of heat output
Modern low-NOx furnaces achieve this using:
  • Advanced burner design
  • Lower flame temperatures
  • Improved combustion control
  • More precise airflow management
 
These systems can reduce emissions significantly compared to older furnaces.
 

What This Means for Furnace Efficiency

 
One of the biggest changes homeowners will notice is the shift toward higher-efficiency equipment.
Many older homes used 80% efficient furnaces
 
These systems were:
  • Reliable
  • Affordable
  • Simple to install
 
Under the new law, standard 80% furnaces without low-NOx technology are being phased out.
Instead, newer systems often include:
  • Higher efficiency ratings
  • Variable-speed motors
  • Sealed combustion systems
  • More advanced electronics
 
Higher efficiency can reduce fuel usage and operating costs over time, especially in colder climates like Colorado.
 

How the New Law Impacts Furnace Prices

 
This is one of the most important concerns for homeowners. The reality is, replacement costs are increasing and will continue to. 
 
Typical cost changes:
Older standard furnace: $4,500 – $6,500
New low-NOx furnace: $7,000 – $12,000
 
These increases are tied to:
  • New manufacturing requirements
  • More advanced components
  • Increased installation complexity
  • Reduced equipment availability
  • Additional service requirements every 2 years
 
In some homes—especially older homes—costs may be higher due to:
  • Venting upgrades
  • Electrical changes
  • System redesign
  • Code requirements

Are Gas Furnaces Being Banned in Colorado?

 
No. Gas furnaces are still allowed in Colorado, but they must meet stricter emissions standards.
After January 1, 2026: Only low-NOx-compliant furnaces can be sold or installed.
This is an important distinction. The law is an emissions standard — not a gas ban.
 

What This Means for Energy Choices in Colorado

 
Over time, the new law may gradually shift the market toward:
  • Higher-efficiency gas systems
  • Heat pumps
  • Hybrid heating systems
  • Electrification options
 
However, gas heating remains:
  • Reliable in cold weather
  • Widely used across Colorado
  • A strong option for many homes
 
Most homeowners will still install gas furnaces—the equipment will simply be cleaner and more advanced.
 

What Homeowners Should Do Right Now

 
You do not need to replace your furnace because of this law, but planning is more important than ever.
We strongly consider replacement as soon as possible if your system is:
  • 10–15 years old
  • Requiring frequent repairs
  • Struggling to heat your home
  • Driving up energy bills
 
Waiting until failure will significantly limit options and increase costs.