Colorado's Model Low Energy and Carbon Code became the state's new minimum energy code on July 1, a shift that will require any city or county updating its building codes going forward to adopt the model code or an equivalent standard that achieves greater energy efficiency and pollution reductions. The code does not mandate all-electric construction, but for the first time it credits the lower energy use of high-efficiency electric heat pumps in ways that make heat pump systems the most cost-effective compliance path for many new homes and commercial buildings statewide.
The Colorado Energy Code Board published the Model Low Energy and Carbon Code in September 2025 under a mandate from state law HB22-1362, which identified buildings as the fifth-largest source of greenhouse gas emissions in Colorado. The code carried a roughly 10-month runway before its July 1 effective date to give local governments, builders and HVAC contractors time to prepare. Any Colorado municipality or county that revises a building code after July 1 must adopt the new model code or a code that goes further on efficiency and emissions, though jurisdictions that leave existing codes untouched are not immediately required to update.
How the Low Energy and Carbon Code Treats Heat Pumps Differently
The code is based on a modified version of the 2024 International Energy Conservation Code, replacing Colorado's previous reliance on the 2021 edition. Rather than mandating electric heating equipment, the code restructures compliance credits so that the substantially lower energy use of electric heat pumps, compared with gas-fired heating and water-heating equipment, translates into fewer additional efficiency measures elsewhere in a building. Colorado Energy Office Executive Director Will Toor said the code "balances the imperatives of minimizing construction costs and maximizing energy savings and pollution reductions" by giving builders multiple compliance pathways rather than a single mandated technology.
A Sliding Scale Tied to Building Size
The code applies a sliding scale based on structure size rather than a single statewide performance target. Homes under 5,000 square feet need only meet the code's baseline requirements, which the Colorado Energy Office says are broadly similar to the 2024 IECC. Homes between 5,000 and 7,499 square feet must achieve 7% to 10% better energy performance than that baseline, and homes of 7,500 square feet or larger must reach net-zero energy performance. An analysis conducted for the National Association of Home Builders found that moving from the 2021 to the 2024 IECC base code would lower new-home construction costs in most Colorado regions by $3,900 to $6,750, depending on whether the home uses gas or electric heat pump heating.
Demand Response Requirements Add a New Layer for HVAC Equipment
The Low Energy and Carbon Code is among the first statewide codes in the country to require that heating, cooling, water-heating and lighting systems be demand-response capable, meaning the equipment must be able to automatically reduce electricity consumption when a utility signals high demand on the grid. The requirement is aimed at helping utilities avoid costly investments in peak generation and transmission capacity that would otherwise be passed on to ratepayers, and it adds a new specification that HVAC manufacturers and installers doing business in Colorado will need to account for in equipment selection going forward.
The code maintains earlier requirements that new construction remain solar-ready, electric-ready and EV-ready, but adds flexibility such as allowing Level 1 electric-vehicle charging spaces at multifamily properties instead of Level 2 chargers, a change intended to hold down costs while preserving future retrofit options. Builders in jurisdictions that had already adopted stretch codes ahead of the July 1 deadline will see less immediate change than builders in counties that had continued operating under the 2021 IECC baseline until now.
HVAC contractors working on new construction in Colorado will need to weigh heat pump equipment selection earlier in the design process, since the code's revised credit structure changes the calculus builders use to hit required energy performance targets under the Low Energy and Carbon Code. The Colorado Energy Office hosted webinars on the code changes in September and has continued offering technical assistance so that contractors and local code officials in jurisdictions that adopt the new requirements can draw on the same resources used to develop the standard, including a codes helpline staffed to answer questions within three business days.
Local Adoption of the Low Energy and Carbon Code Will Roll Out Unevenly
Because the state code only becomes mandatory for a jurisdiction when that jurisdiction next revises its building codes, statewide adoption of the new heat pump-favoring credit structure will phase in over the coming years rather than all at once on July 1. The Colorado Energy Office has set up a codes helpline and a technical assistance program to help local governments and contractors implement the changes, along with training sessions for building department staff and industry professionals navigating the code's compliance options for the first time.
