What ZEHES Actually Is, and What It Does Not Require Yet

By Max Fisher · Published 2026-10-22 · Updated 2026-10-24

Short answer. Maryland has no law today that makes a homeowner replace an oil, propane or gas furnace, boiler or water heater. The Zero-Emissions Heating Equipment Standard (ZEHES) is a rule the Maryland Department of the Environment (MDE) is still developing. It would set emission limits on newly manufactured equipment, not on the systems already in your basement. Heat pump installers already sell equipment that meets it, which is why the rule comes up on sales calls, but nothing about it is in force yet.

This page sticks to what the primary sources say: MDE’s own Clean Heat Rules page, the regional model rule Maryland is considering, and the executive order that started the work. Where the record is thin, we say so.

Where ZEHES came from

On June 4, 2024, Governor Wes Moore signed Executive Order 01.01.2024.19, which directs state agencies to carry out Maryland’s Climate Pollution Reduction Plan. Among other things, it tells MDE to propose two heating rules. MDE now calls them, together, the “Clean Heat Rules”:

The Zero-Emissions Heating Equipment Standard (ZEHES). A product standard for new space and water heating equipment.
The Clean Heat Standard (CHS). A program aimed at the companies that sell heating fuel, not at households.

An executive order is a direction to an agency. It is not itself a rule that applies to you. The rule only exists once MDE writes it, takes public comment and adopts final regulations.

What MDE says ZEHES will and will not do

MDE’s Clean Heat Rules page is the source of record. In its own words, ZEHES “will set emissions limits for newly manufactured residential furnaces, boilers, and water heaters.” The same page is just as clear about the limits of the rule:

It will not apply to cooking equipment.
It will not apply to existing heating systems.
Existing furnaces, boilers and water heaters “can continue to be used, serviced, and maintained.”
The standard will only apply to new systems produced after specific compliance dates “later this decade.”

MDE also notes that Maryland is one of several states considering a common model rule so the Northeast and Mid-Atlantic stay consistent, and that heat pumps already meet the standard and “have become the top-selling heating systems in Maryland.”

The model rule behind it

The model rule MDE links to was published by the Northeast States for Coordinated Air Use Management (NESCAUM) with the Regulatory Assistance Project: Model Rule 1.0, NOx and GHG Emissions Standards for Space and Water Heaters, dated October 30, 2024. It is a template. Each state that adopts it fills in its own dates and exclusions, and some provisions are bracketed for exactly that reason.

As written, the model rule covers equipment sold, leased or installed in the adopting state, and it sorts residential equipment into categories by rated heat input:

Model rule category	What it covers
Category 1 furnace	Furnaces under 225,000 Btu per hour that burn methane gas, heating oil or propane
Category 1 boiler	Boilers under 300,000 Btu per hour that burn methane gas, heating oil or propane
Category 1 water heater	Gas storage water heaters under 75,000 Btu per hour
Category 4 water heater	Oil or propane water heaters up to 210,000 Btu per hour

For those categories, Table 1 of the model rule sets a zero-NOx and zero-greenhouse-gas limit for equipment manufactured or refurbished on or after January 1, 2029. Some gas water heater categories also get an earlier ultra-low-NOx step, set at twelve months after a state adopts the rule.

Two details matter for a homeowner. First, the trigger is the date the equipment was manufactured, not the date your current system was installed. Second, a zero-emission limit is technology-neutral on paper. The rule does not name heat pumps. In practice, equipment that burns fuel cannot emit zero, and equipment that does not burn fuel, such as a heat pump or an electric resistance heater, can.

Where the Maryland rule stands now

The schedule has already moved. MDE’s November 1, 2024 climate implementation plan laid out a path to convert the model rule into a Maryland rule in winter 2025, publish a proposed rule with a public hearing in summer 2025, and adopt it in fall 2025. That target has passed. As of this page’s publication, MDE’s Clean Heat Rules page still describes ZEHES as a standard under development and has not posted final regulatory text.

That leaves the details that most affect a household unsettled: Maryland’s exact compliance dates, which bracketed exclusions it keeps, and how sales and installations would be enforced. Treat any article that states those details as final with suspicion until MDE publishes the adopted rule.

What the Clean Heat Standard is, briefly

The second rule is aimed at fuel providers. MDE describes the Clean Heat Standard as guiding “natural gas utilities and fuel oil or propane delivery companies” to reduce emissions over time by delivering clean heat services, such as installing zero-emission equipment, weatherizing buildings or supplying cleaner fuels, and earning credits for doing so. MDE states plainly that “there is no requirement for individual consumers under this program.” If it works as described, a homeowner’s experience of the CHS would be more offers and incentives from their fuel company, not a mandate.

One related rule is already final, and it also lands on fuel companies, not households. Under MDE’s Heating Fuel Reporting Program, heating fuel providers began collecting delivery data in January 2026 and must file an annual report of monthly fuel delivered in Maryland, by fuel type, sector and county. The first report, covering 2026, is due April 1, 2027.

All of this sits under Maryland’s 2022 Climate Solutions Now Act, which MDE’s clean buildings page says sets a target of net-zero statewide emissions by 2045.

What this means for you today

Question	What the sources support
Do I have to replace my furnace now?	No. MDE says existing systems can keep running and be serviced.
Will I be forced to buy a heat pump in 2029?	No. The model rule limits what new equipment can be sold and installed after its compliance date. It sets no deadline for your existing system.
Can I still buy a gas furnace today?	Yes. Nothing in force in Maryland stops it.
Could buying combustion equipment later get harder?	Possibly, once Maryland adopts a final rule and its dates arrive. The final dates are not set.
Does ZEHES affect my gas stove?	MDE says it will not apply to cooking equipment.

How to plan around it without guessing

If your furnace, boiler or water heater is young and working, ZEHES is not a reason to replace it. If it is near the end of its life, the decision is the same one you would make without the rule: compare a like-for-like replacement with a heat pump on installed cost, operating cost and comfort, using real quotes for your house.

Three practical steps help either way:

Get the house measured first. A home energy assessment and air sealing change what size system you need, whatever the fuel.
Check the incentives that are live. EmPOWER Maryland utility programs are the main ones today. See the rebate stack pillar for what is actually available, including the federal credits that ended after 2025.
Ask installers what they know, not what they fear. A good installer can explain the difference between a proposed rule and an adopted one. If the pitch is “the state is banning furnaces next year,” ask for the regulation number.

How to verify this yourself

We are not the source of record. MDE is. Before you rely on any date:

Read MDE’s Clean Heat Rules page and sign up for its email list.
Read the NESCAUM model rule itself, especially Table 1.
Email MDE at the address on that page with “ZEHES” in the subject, or call 410-537-3890.

When MDE adopts final text, this page will be updated to match it. If you find a primary source that says something different from what is here, tell us and we will correct it.

To compare local companies that install heat pumps, start with your city on the DMV directory.