Heating and Cooling in Charleston County, SC

Heating and cooling in Charleston County depends on which side of the marsh you live on. A condenser on Sullivan's Island, an air handler in a downtown attic and a heat pump in Ravenel fail for different reasons, and the flood rules treat them differently too.

Aero Air Techs is based in Charleston and serves the towns and islands around it. The county had about 408,235 people at the 2020 census, spread over roughly 918 square miles of land. James Island is about 20 minutes by road from our Charleston base and Kiawah Island is about 74, so we start every call with the address.

Heating and cooling in Charleston County, area by area

Use this as a first read of what wears on a system where you live.

Part of the county	What works against your system	What to check first
Sullivan's Island, Folly Beach, Isle of Palms, Kiawah, Seabrook	Salt air and wind-driven sand	Condenser coil, contacts, cabinet screws
The peninsula and older Charleston	Tidal flooding and tight old houses	Unit height, duct routes, drain lines
James Island, Johns Island, Mount Pleasant	Marsh humidity and fast growth	Sizing, drainage, salt near the water
North Charleston	Mixed housing eras, low creek lots	Ductwork and flood zone
Ravenel, Hollywood, Awendaw	Sandy lots, pines and longer drives	Pollen on the coil, run hours

Matching the service to the setting saves a wasted visit.

• Coastal corrosion AC repair from Folly Beach to Isle of Palms. Barrier island units take salt from every direction, and the damage starts low on the cabinet where it is easy to miss.
• AC replacement on flood-zone lots, where the county's height rule can reshape the job. Settle the required elevation for A, AE, AH, AO and A99 zones before comparing equipment prices.
• Ductless mini splits for older peninsula homes with no route for ducts. Historic district rules can limit where an outdoor unit sits, so ask staff before you buy.
• Heat pump repair out toward the airport, where the first freeze averages a month ahead of downtown. A defrost fault may not show up on the peninsula until much later.
• Whole home dehumidifiers for second homes on Kiawah, Seabrook and the barrier islands. Closed-up houses collect moisture quickly in summer, with nobody there to notice it.
• AC maintenance across the county before May. The airport averages 64.3 days a year at or above 90°F, and most of those arrive from June through August.

Salt on the barrier islands

Plan around salt first if you can hear the ocean. Salt film eats coil fins and creeps into electrical contacts, and the damage starts low on the cabinet where it is easy to miss. A gentle fresh-water rinse helps, and so does a yearly look at the contactor and capacitor terminals. When white or green crust shows up, read about coastal corrosion AC repair before you agree to replace anything.

Which flood rule covers your lot?

Find your jurisdiction, then your flood zone. Charleston County's Building Inspection Services says replacement HVAC in A, AE, AH, AO and A99 zones must sit at or above the existing finished floor or the design flood elevation, whichever is lower. A job that counts as a Substantial Improvement must go two feet above base flood elevation.

The City of Charleston has its own guidance. It requires machinery and equipment in the Special Flood Hazard Area, HVAC units and ductwork included, to be raised to the Design Flood Elevation, and it has enforced Coastal A Zone requirements since January 1, 2023. Other incorporated towns write their own rules. Awendaw is one local exception worth knowing: under an agreement with the town, the county runs permitting and inspections there.

Tides are part of daily life on the low ground. The Post and Courier reports that Charleston Harbor reached flood stage 54 times in 2024.

How far apart are the freeze dates downtown and at the airport?

A full month. NWS averages from 1991 to 2020 put the first freeze downtown on December 30, against November 30 on Sullivan's Island and November 27 at the airport in North Charleston. In practice, a heat pump on the peninsula sees few freeze nights, while one out by the airport meets its first freeze weeks earlier. Test your heating before Thanksgiving if you live away from the harbor.

The summer load is the same story everywhere: NOAA's normals show 64.3 days a year at or above 90°F at the airport. Our air conditioning page covers what that does to a system.

Ravenel, Hollywood and the Awendaw side

Farther from the water, the job changes. Salt fades and the concerns become pine pollen on the coil, leaves in the cabinet, sandy soil around the pad and long run hours in big, shaded yards. Charleston County also takes in part of the Francis Marion National Forest, and McClellanville sits up US 17 beyond Awendaw.

Road times reflect that: about 32 minutes to Ravenel, 37 to Hollywood and 44 to Awendaw. Kiawah Island and Seabrook Island run past an hour, about 74 and 65 minutes, so those visits are arranged by phone. Our homepage explains how we work, and the service areas page lists every place by name.