AC Installation in Gaithersburg, MD
A new air conditioner in Gaithersburg will run from June through September every year. Tell us about the house, and a licensed contractor who covers Montgomery County will get in touch.
Tell us about the job
It takes about a minute.
Four months of summer heat to plan for
Gaithersburg summers average 85°F on a June through September afternoon. That is the stretch a new air conditioner has to handle every year, four months of it.
The area has also logged 443 damaging wind events and 58 hail events over the past ten years, some hail over two inches across. The outdoor unit sits outside through that. Any new central air conditioner installed today also has to meet a federal minimum of 14.3 SEER2, so that efficiency floor is already part of what a contractor can install.
- 4 months
- June through September, your air conditioner is on duty
- 85°F
- the average summer afternoon it cools against
- 58 hail events
- in ten years, and hail bends the fins on outdoor coils
- 13.4 SEER2
- the federal minimum any new unit must meet
NOAA nClimDiv, 1991–2020 normals
Going above the federal minimum saves little here, about $10 a year.
Estimates for a typical Montgomery County home, from EIA household energy data, Maryland fuel prices and NOAA climate normals. Your home will differ.
Maryland requires HVAC contractors to hold a state license.
Maryland licenses the contractor, not each job. The state tested that contractor and keeps a record of them before they ever get to your house. That license belongs to the business, so it stays in place whether this is their first air conditioner install or their thousandth.
For this job, that license is what stands behind the company doing the work. Most cities and counties also require a permit for an air conditioner installation, with an inspection once the work is done, so someone from the local building office checks it separately from the state license itself.
Sources: Maryland General Assembly · Maryland Department of Labor
- What size air conditioner does my house need?
- A contractor figures this out with a load calculation, not by square footage alone. That calculation looks at your square footage, your insulation, how many windows face the sun, your ceiling height, and how your ducts are laid out. Two houses the same size can end up needing different tonnage. Getting the size wrong hurts either way. Too small and it runs all the time without keeping up. Too large and it cools the air fast then shuts off before it pulls the humidity down, so the house still feels damp.
- Should I replace the whole system or just the outdoor unit?
- In most cases you want to replace both together. The outdoor unit and the indoor coil are matched to work as a pair. Put a new condenser on an old coil and it usually will not run at the efficiency it is rated for. Some manufacturers will not honor the warranty on that kind of mismatch either. If your coil is old, expect a contractor to recommend replacing it along with the outdoor unit. The one exception is a coil that is new enough and still compatible, which a contractor can check before quoting the job.
- Do HVAC contractors in Gaithersburg need a state license to work on my home?
- Yes. Maryland requires HVAC contractors to hold a state license, issued through the Maryland Board of Heating, Ventilation, Air Conditioning, and Refrigeration Contractors. That license covers the contractor as a business, not each individual job. Installing a new air conditioner also requires a permit from the local building office in most cities and counties, along with an inspection once the work is done. Ask whether that permit is included when you get a quote.