HVAC service in Gaithersburg, Maryland
Gaithersburg's median housing unit dates from 1989, and about three quarters of the city's 27,280 units went up between 1970 and 2009, so whole subdivisions reach replacement age at once. Shemtov Systems repairs, maintains and replaces those systems from Olde Towne and Deer Park east of I-270 to Kentlands, Lakelands and Crown on the west side, and at Gaithersburg addresses outside the city limits. The company is family-owned, has worked across Montgomery County since 1981, and is NATE-certified, licensed and insured. Call 240-355-3333; the answering service picks up when the office is closed.
Key takeaways
- The median Gaithersburg housing unit dates from 1989 and about three quarters of the stock was built between 1970 and 2009, so subdivisions hit replacement age together.
- About 53 percent of occupied city homes heat with utility gas and 43 percent with electricity, covering heat pumps and older resistance heat alike.
- Detached houses are only 17 percent of completed city dwelling units, so tight mechanical closets, three-level swings and units with no ductwork are the norm.
- Replacing a permanently installed HVAC unit needs a mechanical permit: from the City inside the corporate limits, from Montgomery County DPS outside them.
- Montgomery County is climate zone 4A; Dulles normals show about 33 days a year at or above 90 degrees F and 25 nights at or below 20.
What heating and cooling do Gaithersburg homes actually have?
The city has about 27,280 housing units, 25,772 occupied. Roughly 53 percent of those homes heat with utility gas, 43 percent with electricity and 331 households with fuel oil. The Census records fuel rather than equipment, so that electric share covers heat pumps and resistance heat alike. The City's January 2026 dwelling unit report shows why: detached houses are 17.2 percent of completed units, townhouses 27.2 percent, garden apartments and condominiums 38.3 percent. See our residential HVAC services.
Why do so many Gaithersburg systems fail around the same time?
The city grew in waves, so its equipment ages in waves. About 5,540 units date from the 1970s, 5,817 from the 1980s, 4,168 from the 1990s and 4,716 from the 2000s. Kentlands' first residents moved in during 1991; Lakelands was designed next door in 1996; Washingtonian Woods, 576 units, went up in the late 1980s. Against 12 to 17 years for a central air conditioner and 15 to 20 for a furnace, those houses are due a second changeout. See how long HVAC systems last and replacement costs in Maryland.
City permit or county permit for a Gaithersburg address?
It depends which side of the corporate limits the house is on, and that is the first thing to settle. Inside them the City requires a Residential Mechanical Permit to install, or remove and replace, any permanently installed HVAC unit, and the contractor must hold Maryland HVACR and Home Improvement Commission licenses. Address decides it, not the postmark: the three Gaithersburg ZIP codes hold about 47,200 housing units against 27,280 inside the city, so many go to Montgomery County DPS instead. There the equipment sets the inspection count, with WSSC signing off gas-fired work alongside the county and the county alone signing off electric.
Why does sizing go wrong in a three-level townhouse?
By calculation, not by copying the old nameplate. Montgomery County is mixed-humid climate zone 4A, and 1991-2020 normals at Washington Dulles, the nearest full-record airport station, put the July average high at 87.6 degrees F. An oversized system short-cycles, never runs long enough to dry the house and leaves it clammy, a common complaint in three-level townhouses on one system. Size with Manual J, select with Manual S: see what size air conditioner you need.
Is a heat pump a sensible choice in Gaithersburg?
For much of the city it is already in place: about 11,100 occupied households heat with electricity, about 5,490 of 8,650 in ZIP 20879. Dulles runs colder at night than the region's other airport stations and still averages only 25 nights a year at or below 20 degrees F. A correctly sized heat pump with backup heat and a sensible balance point covers a 4A winter; cold-climate models hold more capacity at low temperatures. Compare furnace vs heat pump in Maryland or our heat pump service.
What if my home has no ducts, or ducts that were never right?
Two cases recur. First, Olde Towne: ZIP 20877 holds about 503 units built in 1939 or earlier, and a house on radiators or baseboard has no ductwork to reuse. Second, the city's 8,033 garden apartment and 2,989 garden condominium units, where a mechanical closet leaves no room for an air handler and duct trunk. A ductless mini-split suits both. Where ducts exist, 1970s and 1980s runs are often leaky or badly balanced, and duct sealing and zoning fixes more complaints than a new condenser.
What heating problems are specific to Gaithersburg winters?
Gas comes from Washington Gas; MC311 directs electric outages to Pepco. About 13,772 occupied city households burn gas, so cracked heat exchangers, failed igniters and blocked flues are the usual winter failures. Fuel oil has not vanished: about 946 households in ZIP 20878 still burn oil or kerosene, the usual conversion candidates. With roughly 102 freezing nights a year, a heat pump stuck on backup strips shows up fast on the bill. See furnace repair and replacement and signs you need HVAC repair.
How many run hours does Gaithersburg equipment log?
A heat pump earns two visits because it works all twelve months; a separate furnace and air conditioner can manage on one each. Dulles normals show about 4,604 heating degree days and 1,233 cooling degree days a year, so neither side of the system rests for long. Book cooling service in spring and heating service in fall, and treat the filter and the clearance around the outdoor unit as calendar items rather than symptoms, which is harder than it sounds on the alley-loaded lots of Kentlands, Lakelands and Crown. A service agreement bundles both visits.
Frequently asked questions
Do you work west of I-270 as well as Olde Towne?
Both sides. East of the highway that is Olde Towne, Deer Park, Saybrooke, Diamond Farms and Washingtonian Woods; west of it Kentlands, Lakelands, Crown, Potomac Oaks and Quince Orchard Park. ZIP codes 20877, 20878 and 20879 are all covered, city limits or not.
Can I reach you at night or on a weekend?
Yes. The 24-hour answering service takes 240-355-3333 outside office hours and passes the job on, which is when marginal systems tend to quit.
Do you handle the Gaithersburg mechanical permit?
Yes, and we confirm which authority covers the address before filing. We are licensed and insured in Maryland and Washington DC and pull the permit with the job.
Has the EmPOWER rebate changed for gas equipment?
Yes, and it matters here because so much of the city burns gas. A 2024 law added incentives for moving off fossil fuel heating; a 2025 law removed EmPOWER incentives for natural gas equipment. What is claimable therefore depends on which way the replacement goes, so we confirm the live terms at quote rather than promise a figure.
My neighbors are all replacing systems. Am I next?
Possibly. Gaithersburg subdivisions were built out in tight windows, so their original equipment ages together. If your system is original to a 1980s or 1990s house or still runs on R-22, price replacement against repair. Anything installed since January 1, 2025 sits under a 700 GWP refrigerant limit, so R-410A is legacy too.
Talk to Shemtov Systems
Whole streets in Gaithersburg came of age together, and their equipment is doing the same. Call Shemtov Systems on 240-355-3333 to have a system assessed before the subdivision's replacement wave reaches your house. Family-run since 1981, NATE-certified, and someone on the phone at any hour.
Services we provide
Family-owned since 1981. Call 240-355-3333.
Other areas we serve
Shemtov Systems covers Montgomery County and the Washington DC metro.