The short answer
For most houses on the Georgia and South Carolina coast, a heat pump is the natural fit: winters are mild, so it heats efficiently most of the season, and one system also cools. A gas furnace, or a dual-fuel pairing, makes more sense where gas is already piped in and the running costs favor it.
How does each one make heat?
A gas furnace burns fuel and blows air across a heat exchanger. A heat pump makes no heat at all: it moves heat that is already in the outdoor air into the house, using the same refrigerant cycle as an air conditioner run in reverse. Moving heat takes far less energy than making it, which is where a heat pump's efficiency comes from.
As the outdoor temperature falls there is less heat to move, so a heat pump's capacity drops. Below a certain point auxiliary heat — usually electric resistance strips — makes up the difference, and auxiliary heat is expensive to run.
Why do heat pumps suit a mild coastal winter?
The Department of Energy's summary is that in moderate climates heat pumps can be an energy-efficient alternative to furnaces and air conditioners. The coast is the textbook case: long, hot summers where the heat pump is simply the air conditioner, and short winters where most nights are well within what it handles without help.
What matters is how the controls are set up. A heat pump that calls for auxiliary heat too readily can produce a winter bill that erases its advantage — which shows up as a surprising bill rather than as a comfort complaint.
When does a gas furnace still make sense?
- Gas is already piped to the house, and replacing a furnace keeps an existing, working setup
- An older, leakier house loses heat quickly on the few genuinely cold nights
- Your gas and electric rates make gas the cheaper heat per unit delivered
- You prefer the hotter supply air a furnace produces
A furnace still needs an air conditioner beside it for the summer, so the comparison is a heat pump against a furnace plus an AC — not a heat pump against a furnace alone.
What is dual fuel?
A dual-fuel system pairs a heat pump with a gas furnace. The heat pump does the heating on mild days, which is most of a coastal winter, and the furnace takes over below a switchover temperature the installer sets. Where gas is already available, it combines the heat pump's efficiency with the furnace's capacity on the coldest nights.
How do efficiency ratings compare?
Heat pumps are rated in HSPF2 for heating and SEER2 for cooling; since 2023 the federal minimum for a split-system heat pump has been 14.3 SEER2 and 7.5 HSPF2. Furnaces are rated in AFUE, the percentage of the fuel's energy that ends up as heat in the house.
The ratings do not settle the question on their own, because the cost of each unit of heat depends on local gas and electric prices. Ask for an estimated annual running cost for each option on your house.
What about safety?
A gas furnace brings combustion into the house, which is why a yearly inspection that includes the heat exchanger matters, and why working carbon monoxide alarms are essential. A heat pump has no combustion, so there is no carbon monoxide risk from the heating itself.
For replacement budgets, heat pump installation starts at $5,995, a furnace replacement at $3,750, and a complete AC-plus-heating system at $8,250.
Also asked.
- Do heat pumps work in Savannah winters?
- Yes. Coastal winters are mild, so a heat pump handles most of the season on its own, with auxiliary heat covering the occasional cold night. Correctly configured controls keep auxiliary heat to those nights.
- Why does heat pump air feel cooler than furnace air?
- A heat pump delivers a larger volume of air at a lower temperature than a furnace. The air is warmer than the room, but cooler than your skin, so it can feel cool at the register while still heating the house.
Sources
- ↗Heat Pumps — U.S. Department of Energy
- ↗2023 Central Air Conditioner and Heat Pump Standards: Frequently Asked Questions — U.S. Department of Energy
- ↗Carbon Monoxide Information Center — U.S. Consumer Product Safety Commission