A heat pump costs far less to run than electric heat in South Carolina: $19.67 per million Btu delivered, against $46.69 for baseboard. Gas is the open question, because its price depends on your utility. Below is how to compare it fairly, what the local climate does to the numbers, and the houses where a furnace still comes out ahead.
The short answer for South Carolina
Start with the one comparison the data supports directly. At the state’s average residential electricity price, a heat pump rated at 8.1 HSPF2 (a seasonal COP of about 2.4) delivers a million Btu of heat for $19.67. Electric resistance, such as baseboard heaters or an electric furnace, delivers the same million Btu for $46.69. That puts the heat pump $27.02 per million Btu below resistance. The figures are computed from average residential prices published by the U.S. Energy Information Administration and the ENERGY STAR cold climate minimum of 8.1 HSPF2 for ducted systems.
Gas prices differ from one utility to the next, so take the rate from your gas bill or your utility’s rate sheet and compare it to the $19.67 heat pump figure using the method in the next section.
These numbers compare running cost for the same unit of delivered heat. They leave out your yearly bill, which depends on the size and tightness of the house, and the cost of equipment and installation.
The practical rule: if the gas on your bill works out to more than $19.67 per million Btu of delivered heat, the heat pump is the cheaper system to run, and against electric resistance it wins by a wide margin.
What each option costs to run in South Carolina
| System | Efficiency used | Cost per million Btu delivered |
|---|---|---|
| Electric resistance (baseboard) | 100% efficient | $46.69 |
| Heat pump | 8.1 HSPF2 (seasonal COP about 2.4) | $19.67 |
Both rows rest on the same electricity price: 15.93 cents per kWh, the average residential rate for the state in the year-to-date period through July, from the EIA’s Electric Power Monthly. A statewide average hides real differences between utilities and rate plans. Use it to compare fuels and to estimate, then check your own bill.
A kilowatt-hour holds 3,412 Btu. Baseboard heat turns all of it into warmth, while a heat pump with a seasonal COP of about 2.4 moves roughly 2.4 times as much heat as the electricity it draws. Same price per kWh, far fewer kWh. That is why efficiency counts as much as the fuel price.
How do you compare a gas furnace to these numbers?
Take the price of gas per unit from your bill, then divide by the Btu in that unit. That gives the cost per Btu of fuel. Next divide by the furnace’s efficiency, which is printed on the unit or its spec sheet, and scale up to a million Btu. The result is the cost of a million Btu delivered into the house, directly comparable to $19.67. Always compare cost per million Btu of delivered heat, because a price per kWh and a price per gas unit cannot be set side by side.
The heat pump figure uses 8.1 HSPF2, the ENERGY STAR cold climate minimum for ducted split systems and single-package units. The same cold climate tier asks 8.5 HSPF2 of non-ducted (ductless) systems. Standard ENERGY STAR certification asks less: 7.8 HSPF2 for split systems and 7.2 for single-package units. A unit rated at those levels would run above $19.67. A ductless unit has no duct losses, so it begins with an edge and has to be better to earn the cold climate designation. These are minimums, so a higher-rated unit would run cheaper than $19.67. If you are weighing ratings, what HSPF2 measures, and why ductless asks for more explains the gap.
How cold it gets, and what that does to a heat pump
Heating degree days turn a climate into a cost. For every day of the year they add up how far the average temperature sat below 65°F. At Charleston International Airport, NOAA’s 1991-2020 normals show about 1,844 heating degree days a year, the mild end of the scale. The coldest month there has a mean daily minimum of 38.9°F, which stays above freezing.
The $19.67 figure uses a seasonal efficiency, an average across the whole heating season. A heat pump’s output drops as the air outside gets colder, and in deep cold a backup source carries the coldest nights, either resistance strips inside the unit or a furnace. Where the average low in the coldest month is 38.9°F, the machine spends nearly all its hours in its efficient range, and the backup has little to do. Along the coast, the seasonal number is a fair picture of what a heat pump will do.
Does a heat pump still work in the colder parts of the state?
Yes, but the coastal figure is one reference point. Inland areas and higher ground run colder than Charleston, so the heating season there is longer and the cold nights more frequent. More cold hours mean more backup heat, and the bill drifts up from the $19.67 figure. For a closer look at how output changes with temperature, see how cold is too cold for a heat pump. The heating season in your county tells you how many of those cold stretches to plan for.
On the coast, price the system for the mild-winter case, and in the colder interior, ask what backup heat comes with the unit and how it is controlled.
What homes in South Carolina already heat with
The federal Residential Energy Consumption Survey (RECS) for 2020 gives the state’s mix. Electricity is the main heating fuel in 64% of homes, natural gas in 28%, and propane in 5%. By equipment, 46% of homes have a furnace and 41% have a central heat pump. These are state shares from a national survey, so they describe the state and say little about your street.
Because electric heat is the main fuel for most households, many houses are already wired for electric heating. An electrician should still confirm that the panel and circuits can take a heat pump.
A house with no gas line changes the comparison. Without gas service, a heat pump competes with electric resistance or propane, and the $27.02 gap per million Btu against resistance settles most of the question. Running a new gas line has its own cost and a wait on the utility.
A boiler house is a different conversion. Radiators and baseboard hot-water pipes have no ducts, so a central heat pump has nowhere to send its air. Ductless heads avoid the problem, and ductless or central lays out the tradeoff. If your house has ducts, swapping a furnace for a heat pump is the simple conversion, and if it has none, price ductless heads first.
When the other choice wins
The heat pump is cheaper to run than resistance by a wide margin, but it does not win every house. A few situations tilt the other way.
When does keeping a gas furnace make sense?
The first is cheap gas. If your utility’s rate works out below $19.67 per million Btu delivered, the furnace costs less to run, and the extra margin would also have to cover the price of switching. The second is an old system with years left. A furnace that still heats the house reliably has already been paid for, so repairing a furnace or replacing it is worth working through before you commit to a swap.
The third is a dual-fuel setup, where a heat pump handles most of the season and a gas furnace takes over on the coldest nights. That pairing makes the most sense in the colder interior, where backup hours add up. Along the coast, with a coldest-month minimum of 38.9°F, the furnace half of the pair would sit idle for most of the winter.
What if you need air conditioning too?
This one favors the heat pump. Charleston logs about 2,434 cooling degree days a year, more than its 1,844 heating degree days. A house that needs a new air conditioner anyway can get heating and cooling from one heat pump, while keeping a gas furnace means buying a separate cooling system as well. Look at the SEER2 rating for cooling (ENERGY STAR asks for at least 15.2) and the HSPF2 rating for heating, and compare like with like.
Last, a leaky house erodes any running-cost edge. Heat escaping through the attic or walls raises the load for either system and can push a heat pump into more backup hours. Insulation and air sealing cut that load and often let you buy a smaller unit. Before you pick a system, find out your gas rate per million Btu delivered and check how tight the house is. Those two checks decide most cases.
Common questions
Is a heat pump cheaper than a gas furnace in South Carolina?
It depends on your gas rate. A heat pump at 8.1 HSPF2 delivers a million Btu for $19.67 at the state’s average residential electricity price. Work out the same figure from your gas bill and furnace efficiency, and the lower number is the cheaper one to run.
Does a heat pump need backup heat in South Carolina?
Along the coast, the coldest month has a mean daily minimum of 38.9°F, so backup rarely has much to do. Inland and higher areas get colder, and a backup source, either resistance strips or a furnace, carries the coldest nights there. Ask the installer how it is set up.
What HSPF2 rating should I look for?
ENERGY STAR’s cold climate tier sets 8.1 HSPF2 for ducted split and single-package heat pumps and 8.5 for non-ducted systems. Standard certification asks 7.8 for split systems and 7.2 for single-package units. These are minimums, and a higher rating runs cheaper. Compare HSPF2 to HSPF2 for heating and SEER2 to SEER2 for cooling.
Can I switch if my home has no gas line?
Yes. Electricity is the main heating fuel in 64% of South Carolina homes, and a central heat pump is the main heating equipment in 41% of all homes in the state. Without gas, your comparison is heat pump against electric resistance, where the heat pump runs $27.02 less per million Btu.