The battle between building owners and state mandates for energy efficiency, which they say will cost billions to comply with, ratcheted up a notch when the building associations involved in a recent lawsuit against the state and the City and County of Denver sent a letter to U.S. Attorney General Pam Bondi requesting that the Department of Justice investigate potential violations of federal law.

The letter from the Colorado Hotel and Lodging Association, Apartment Association of Metro Denver, Colorado Apartment Association, and National Association for Industrial and Office Parks-Colorado asks the atorney general to “evaluate and consider taking action on the Colorado Electrification Mandates to enforce the federal government’s interest under EPCA in a uniform national energy policy and to enforce EPCA’s waiver application requirement for state and local governments who attempt to regulate existing buildings and the covered products therein without federal permission.”

The dispute is over Colorado’s and Denver’s regulations that large building owners must meet strict energy reduction standards that the owners say would effectively eliminate the use of natural gas and impose electrification mandates on large buildings that could cost building owners as much as $3.1 billion, according to the Air Pollution Control Division’s economic impact report.

“The Building Performance Standards (BPS) rules offer flexibility to building owners, providing multiple compliance pathways to achieve the required emissions reductions through a combination of electrification, energy efficiency improvements, and/or onsite clean energy generation,” said a spokesperson for the Colorado Energy Office in a statement to The Denver Gazette. “The BPS rules do not require electrification.”

Building owners say the regulations are onerous, expensive, sometimes impossible to comply with, and violate federal law.

Since the election of President Donald Trump, the regulatory atmosphere at the federal level has made an abrupt turnaround from the Biden administration’s policies.

Trump issued an executive order on April 8, 2025, saying, “It is the express policy of the United States to prevent state and local interference in matters of lawful domestic energy use, appliance standards, and infrastructure flexibility.”

The order directed the attorney general to “prioritize the identification of any such state laws purporting to address “climate change” or involving “environmental, social, and governance” initiatives, “environmental justice,” carbon or “greenhouse gas” emissions, and funds to collect carbon penalties or carbon taxes.

“The sttorney general shall expeditiously take all appropriate action to stop the enforcement of state laws and continuation of civil actions…that the attorney general determines to be illegal,” the order states.

Trump said his administration is committed to “unleashing American energy” by removing “illegitimate impediments” to energy development, production or use of oil, natural gas, coal, hydropower, geothermal, biofuel, critical mineral, and nuclear energy resources.

A lawsuit over state Regulation 28 and the Energize Denver regulations that specify mandatory energy use reductions for large buildings filed April 24, 2024 by the building owner associations was dismissed in late March because, said the judge, the plaintiffs lacked standing to sue. However, U.S. District Court Judge Regina M. Rodriguez gave the plaintiffs time to amend their complaint and refile the complaint. The deadline is June 10.

The federal Energy Conservation and Production Act sets national energy efficiency standards for a range of products, including stoves, HVAC equipment and water heaters, which the plaintiffs say are affected by the state and Denver’s energy efficiency regulations.

A provision in the federal law prohibits state or local government policies or regulations that require people to use what the law calls “covered products” that are more efficient than the federal standards.

According to legal experts, the ECPA was enacted to make sure that energy efficiency standards for this type of equipment are uniform across the country to avoid a patchwork of appliance standards that would make it difficult for manufacturers to meet, and to reserve setting such standards to the federal government’s policies on energy efficiency.

“Significantly, the Colorado Electrification Mandates do not just target new buildings but will require the forced electrification of thousands of existing buildings. EPCA expressly preempt state or local energy conservation standards for existing buildings unless the state or locals files a petition seeking a waiver from the Secretary of Energy,” said the letter. “(There is an) urgent need to rein in overreaching local ‘decarbonization’ mandates that undermine domestic energy security and Federal consumer protections.”

The District Court said, “At the heart of this lawsuit is the question … of whether Congress intended the EPCA to preempt state and local regulation of emissions that address the energy use and GHG emissions of buildings as a whole, even if they do not specifically regulate covered products.”

“I think that’s a good argument,” Buchalter law firm Special Counsel Jack Luellen told The Denver Gazette in an interview. “I think when you start saying that we have to rein in overreaching, local decarbonization, that goes against the idea of federalism in some respects. If Colorado decides they’re more concerned about greenhouse gases or whatever else, why shouldn’t they be able to regulate that in a way that doesn’t violate a field that’s been directly preempted?”

Neither the state nor the city regulations directly regulate appliance efficiency, but the plaintiffs argue that the standards are, in some cases, unachievable without requiring the replacement of natural gas appliances with electric versions, and that this indirectly affects appliance efficiency by denying consumers access to the appliances of their choice that meet the federal standards.

The federal statutes prohibit actions that indirectly affect appliance efficiency. A recent Supreme Court case out of Berkeley, California, held that a building code that prohibited the installation of natural gas piping to a building, making the use of gas appliances impossible, violated the ECPA.

The state denies that the ECPA applies and that the regulations are reasonable and necessary to achieve Gov. Jared Polis’ greenhouse gas reduction goals, and to that end the General Assembly passed a bill that clarifies some procedures and creates a new state-owned enterprise that will collect fees from building owners to provide assistance in meeting the standards.

“Many other building owners and organizations have been working diligently to ensure a successful program. To that end, based on the input from a broad range of stakeholders, including many organizations that represent buildings covered by the standards, the Colorado Legislature made improvements to the BPS program in a bill signed by Governor Polis this week,” the statement continued. “HB25-1269 provides for more technical assistance for building owners, as well as some additional flexibility and time to ensure all buildings can achieve the 2030 reduction targets. Colorado awaits and will follow any legal rulings.”