You can rent a City of Boulder ADU, with a license, for long stays. You cannot list it for short stays. This page covers both rules, plus the energy requirements that apply to rented units.
It describes what the rules permit. It says nothing about what a unit might earn, because that is not something we will estimate.
Long-term renting#
Allowed with a city rental license.
A license is not a formality. It brings inspection and standards with it, and those differ depending on whether the unit is attached or detached.
The license carries a fee: Being confirmed with City of Boulder.
Short-term renting#
Banned for both the ADU and the main house, unless the ADU and its rental license predate February 1, 2019.
Two things in that rule catch people out. First, the ban reaches the main house, not just the ADU: adding an ADU affects what you can do with the property as a whole. Second, the exemption is narrow and historic. If the ADU and its license do not both predate the cut-off, it does not apply to you.
SmartRegs#
Boulder applies an energy standard to rental housing, and how it lands depends on the form of your unit: Detached ADUs must meet SmartRegs when rented; attached ADUs are exempt; the main home must comply when it is rented.
So a detached ADU has to meet SmartRegs to be rented, an attached one does not, and renting out the main house brings the main house into scope. Worth knowing before you choose between attached and detached.
Owner occupancy#
You do not have to live on site: Not required since March 8, 2025.
What you still cannot do#
The ADU cannot be sold separately from the main home. An ADU is a second home on your lot, not a second property to sell.
Affordable ADUs#
If the unit was built under the affordability allowance, the rent is capped and the commitment is recorded: Rent capped at 75% of area median income, with a Declaration of Use recorded against the property. That obligation stays with the property.