Contractors active in Maryland county permit records, grouped from public filings. Counts reflect permits attributed to each firm. Not every filing names a contractor, so counts here are a floor. A firm's actual permit activity is usually higher.
| Contractor | Trade | Counties | Permits | Last active |
|---|---|---|---|---|
| CONSTELLATION HOME | HVAC | Frederick County, Howard County | 363 | Jul 2026 |
| ENVIRONMENTAL SYSTEMS ASSOCIATES LLC DBA CROPPMETCALFE | HVAC | Howard County | 154 | Jul 2026 |
| ANTHONYS ELECTRIC | HVAC | Howard County | 61 | Jul 2026 |
| ERIC SMOCK HEATING & A/C INC | HVAC | Frederick County | 56 | Jul 2026 |
| AMERICAN RESIDENTIAL SERVICES, ARS OF LAUREL #8551 | HVAC | Howard County | 47 | Jul 2026 |
| HORIZON SERVICES MD LLC | HVAC | Howard County | 34 | Jul 2026 |
| MICHAEL AND SON SERVICES, INC. | HVAC | Frederick County, Howard County | 23 | Jul 2026 |
| UNITED AIR TEMP | HVAC | Frederick County, Howard County | 23 | Jul 2026 |
| HORIZON SERVICES | HVAC | Howard County | 21 | Jul 2026 |
| TRI-STATE HOME SERVICES | HVAC | Frederick County | 21 | Jul 2026 |
| PUTMAN PLUMBING INC | HVAC | Frederick County | 19 | Jul 2026 |
| BLUE DOT SERVICES | HVAC | Howard County | 18 | Jul 2026 |
| BRYAN MOBERLY PLUMBING SERVICES | HVAC | Howard County | 18 | Jul 2026 |
| B & B AIR CONDITIONING & HEATING | HVAC | Howard County | 17 | Jul 2026 |
| F.H. FURR PLUMBING, HEATING, AIR CONDITIONING, & ELECTRICAL | HVAC | Howard County | 16 | Jul 2026 |
| LARRY & SONS INC | HVAC | Frederick County | 15 | Jul 2026 |
| MARYLAND ELECTRICAL SOLUTIONS | HVAC | Howard County | 15 | Jul 2026 |
| Tuckers Air Conditioning, Heating and Plumbing | HVAC | Frederick County | 15 | Jul 2026 |
| EDGE ENERGY | HVAC | Howard County | 14 | Jul 2026 |
| F.H. FURR PLMB, HTG, & A/C | HVAC | Frederick County | 14 | Jul 2026 |
| HUNT PLUMBING HEATING AND AIR CONDITIONING, LLC | HVAC | Howard County | 14 | Jul 2026 |
| WESLEY BARR | HVAC | Frederick County | 13 | Jul 2026 |
| BRICK STREET CONSTRUCTION, LLC | HVAC | Frederick County | 12 | Jun 2026 |
| LEN THE PLUMBER HEATING & AIR | HVAC | Howard County | 11 | Jun 2026 |
| RON AIR INC | HVAC | Howard County | 10 | Jul 2026 |
| WALTS MECHANICAL SERVICES INC | HVAC | Howard County | 10 | Jun 2026 |
| ARUNDEL COOLING & HEATING CO INC | HVAC | Howard County | 9 | Jul 2026 |
| B AND B AIR CONDITIONING AND HEATING | HVAC | Howard County | 7 | Jun 2026 |
| F.H. FURR PLUMBING, HEATING, AIR CONDITIONING, AND | HVAC | Howard County | 7 | Jul 2026 |
| GREEN ELECTRIC SOLUTIONS LLC | HVAC | Howard County | 7 | Jul 2026 |
| MCCREA EQUIPMENT COMPANY | HVAC | Frederick County | 7 | Jul 2026 |
| MICHAEL & SON SERVICE INC | HVAC | Howard County | 7 | Jun 2026 |
| N.E. BOB WALTZ PLUMB/HTG-JEFF | HVAC | Frederick County | 7 | Jul 2026 |
| AMERICAN RESIDENTIAL SERVICES | HVAC | Frederick County | 6 | Jul 2026 |
| AMERIGAS PROPANE L.P. DBA SERVICEMARK | HVAC | Howard County | 6 | Apr 2026 |
| GAITHERSBURG AIR CONDITIONING& HEATING | HVAC | Howard County | 6 | Jul 2026 |
| KASTNER PLUMBING & HEATING INC. | HVAC | Howard County | 6 | Jun 2026 |
| WITKOWSKI MECHANICAL | HVAC | Howard County | 6 | Jun 2026 |
| AMAZING HEATING & AIR CONDITIONING, INC. | HVAC | Howard County | 5 | Jul 2026 |
| ANTHONY W PETROLLE | HVAC | Frederick County | 5 | Jul 2026 |
| EXCEL MECHANICAL | HVAC | Howard County | 5 | Jul 2026 |
| M&A HEATING AND COOLING | HVAC | Howard County | 5 | Jun 2026 |
| MARYLAND HEATING & COOLING | HVAC | Howard County | 5 | Jul 2026 |
| ST JOHN PROPERTIES INC | HVAC | Howard County | 5 | Jul 2026 |
| BAY AREA MECHANICAL SERVICES, INC | HVAC | Howard County | 4 | Jul 2026 |
| BURIC'S HEATING & AIR CONDITIONING, INC. | HVAC | Howard County | 4 | Jul 2026 |
| C.M.H. LLC DBA CROPPMETCALFE | HVAC | Howard County | 4 | Jul 2026 |
| GLM MECHANICAL SERVICES INC. | HVAC | Howard County | 4 | Jun 2026 |
| HVACR 05010083311 | HVAC | Howard County | 4 | Jun 2026 |
| MICHAEL TRASK BODYCOMB | HVAC | Howard County | 4 | Jul 2026 |
Source: county permit records. Updated monthly.