Heating and Cooling in Jefferson County, MO

Heating and cooling in Jefferson County, MO is more electric than most people expect. The Census Bureau's 2020-2024 American Community Survey shows 58 percent of occupied homes heating with electricity, 32 percent with utility gas and 7.1 percent with propane or other tank gas. Kenan Corporation is about 1 hour 30 minutes from Hillsboro, the county seat, in normal traffic. We say so at the start because a drive that long needs a phone call before anyone loads a vehicle.

Heat pumps first, propane second

The county has 93,955 housing units with a median build year of 1987, and 80 percent are detached houses. Another 9 percent are manufactured homes, and 29 percent were built since 2000. With few pre-1940 buildings (3 percent), the question is rarely about boilers or radiators. It is about electric heat, tank gas and long duct runs.

That makes three service profiles. A heat pump home calls about frozen coils, weak heat and failed defrost controls. A propane home has a tank, a regulator and an orifice sized for LP gas, and each has to be right. A manufactured home has under-floor ducts that tear or disconnect. Our heat pump vs furnace guide helps with the replacement decision.

Four decades of growth that put second systems on the calendar

Jefferson County grew by 58.6 percent in the 1960s and 38.9 percent in the 1970s, then by 17.2 percent in the 1980s and 15.6 percent in the 1990s, according to census figures. Growth fell to 3.7 percent in the 2010s.

That curve explains the 1987 median build year. A house from the boom is now four decades old, and a central air conditioner or furnace rarely lasts that long, so most are on their second or third system. The practical question is how old the current unit is and what ducts it is connected to, because a replacement does not fix leaking ductwork.

Jobs rural and suburban county homes call about

Five kinds of work cover most of the county.

County licensing, cities and who pulls the permit

Jefferson County has no single answer for every address. The county's Code Enforcement office at 725 Maple Street in Hillsboro handles unincorporated areas, and the Citizen Portal takes permit, inspection and contractor license applications online. The county posts a Mechanical Contractor License Application, new applicants file an application for examination, and Code of Ordinances Section 500.200 governs licenses. The page states no fees or classes, so confirm both with the office at 636-797-5310.

Cities such as Arnold and Festus run their own offices. Missouri has no statewide HVAC license, so ask any contractor, including us, for the license number your jurisdiction accepts. Get the permit holder named in the written quote.

Imperial, High Ridge, Arnold, Festus: which office covers the address

Imperial and High Ridge are census-designated places rather than cities, so they have no city building office, and the county's Code Enforcement office is the one to ask. Eureka lies mostly in St. Louis County with a part in Jefferson County, so an address there needs a call to the city before anyone quotes the permit.

Arnold says only City-licensed contractors may work inside the city, with a business license from the City Clerk and proof of insurance. Its building desk is 636-282-2378. Festus has a Building Department at 636-937-4694, but its permit page does not address residential HVAC, so call before work starts.

What a call from Jefferson County looks like

Call with the address, the equipment type and the fuel. The technician diagnoses before replacing parts, explains the fault in plain language and gives a clear, upfront quote before work starts. For a county call, we confirm timing before we leave, and we offer same-day service when the schedule allows.

Utilities, rivers and landmarks

Hillsboro, Arnold, De Soto, Festus and Herculaneum are among the county's cities. Utilities vary by address across the county, so check whether your electric bill comes from Ameren Missouri or a cooperative. Ameren's 2026 chart applies only to its customers. I-55 is the main route, and the Mississippi River forms the eastern boundary, with Big River and Meramec among its township names. We list pages for Arnold and Festus. See heat pump installation and furnace repair.