AC units, heat pumps and generators across the DC area
Where can outdoor mechanical equipment go? The rules differ at every jurisdiction line. Here is the short answer for each.
Disclaimer: This is general information, not legal or professional advice for any one property. Codes change. SetbackIQ is not a zoning determination, a permit, or a survey, and it does not replace an architect, engineer, or lawyer. Confirm with your building and zoning offices before you build, buy, or sign a contract.
| Where | Short answer |
|---|---|
| Washington, DC | New and replacement AC units, heat pumps and generators all need permits in DC. AC units and heat pumps may not exceed 60 dBA at the property line at any hour. The general residential limit is 60 dBA by day and 55 dBA at night. |
| Montgomery County, MD | AC units, heat pumps and generators may project up to 5 ft into a front or rear setback. Even replacing heating equipment needs a permit. Noise at the property line: 65 dBA by day, 55 dBA at night. |
| Prince George's County, MD | Residential noise is limited to 65 dBA by day (7 a.m. to 10 p.m.) and 55 dBA at night at the receiving property, which covers AC units, heat pumps and generators. New systems and generators need DPIE permits. Gas piping is regulated separately. |
| Alexandria, VA | AC units, heat pumps and generators may go in side and rear yards only if they stay at or under 55 dBA at every property line. Not in the front yard. The city noise code holds residential property lines to 55 dBA too. |
| Arlington County, VA | AC units, heat pumps, pool equipment and generators may sit in side and rear yards at least 8 ft from a side line and 10 ft from the rear line. Screened with a fence or plantings, they may sit closer, even in a front yard. |
| Fairfax County, VA | AC units, heat pumps, pool pumps and generators may extend 5 ft into a setback but must stay at least 5 ft from every lot line, and each unit must be 10 ft wide or less. The noise ordinance covers all of them. |
Towns and cities inside these counties (for example, Rockville, Gaithersburg, Bowie, Laurel, Herndon, Vienna, and Falls Church) have their own rules.