St. Marys and Calvert County Maryland HVAC Services   ♦   We Make Your Air Flow!

Southern Maryland
St. Marys and Calvert County Maryland HVAC Services
We Make Your Air Flow!


Southern MD air conditioning repairs


Great Mills Heating and Air Conditioning, Inc. is a locally owned and operated full service residential, business and commercial heating and air conditioning contractor.

We have been repairing, servicing, and installing Carrier equipment and others in Southern Maryland in St. Mary's County and Southern Calvert County (Prince Frederick & South) since 1972. Great Mills specializes in the repair, maintenance and replacement of existing residential and commercial comfort control systems.

Some of our many HVAC services include: heating repair in Southern Maryland, furnace repair in Southern Maryland, oil furnace repair in Southern Maryland and gas furnace repair in Southern Maryland. We are a heating contractor in Southern Maryland, oil furnace contractor in Southern Maryland, gas furnace contractor in Southern MD.

Southern MD Heat Pumps, Heating & Cooling System Installation Services & System Types:


  • Direct Heating & Cooling System Replacement
  • Heating & Cooling System Service & Repair
  • Oil Tank Installations
  • Oil Tank Service & Repair
  • Oil Furnaces
  • Oil Furnace Service & Repair
  • Gas Furnaces
  • Gas Furnace Service & Repair
  • Propane Furnaces
  • Propane Furnace Service & Repair

  • Radiant Heating
  • Radiant Heating Service & Repair
  • Heat Pumps
  • Heat Pump Service & Repair
  • Air Conditioning
  • Air Conditioning System Service & Repair
  • Heating & Cooling Zoning
  • Heating & Cooling System Service Agreements
  • Heating & Cooling System Service & Repair

Southern MD heat pumps

Our Technicians


Great Mills Heating and Air employs NATE-certified technicians who have proven their knowledge in the HVAC/R industry by passing specialized NATE certification tests. Choose Great Mills for superior installation and maintenance or service of your heating, ventilation, air conditioning or refrigeration system to get the job done right the first time. SMECO Recommends Great Mills Heating and Air as a heating and air conditioning contractor with Nationally Certified Technicians with proper insurance and licensing.


Ask us about Geothermal Heating and Cooling Systems

Great Mills Heating and Air also installs geothermal systems for homes.

Geothermal vs. Ground Water vs. Water Furnace Geothermal energy has been used to heat and air condition buildings for several decades. Other terms for these geothermal systems include geo-thermal, geoexchange, ground-water, ground-water assisted, ground-water-source, water-to-water, and even water furnace heating and cooling.

Geothermal heat pump technology taps the energy in the earth's surface and drive a heating and air conditioning system for both residential and commercial uses. The result is a green or natural heat pump that saves energy and benefits the environment.

St Marys HVAC


Southern Calvert heating Air
Carrier Dealer So MD
Puron refrigerant MD
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