Heat Pump Payback in Summerville, SC
Should Summerville switch to a heat pump?
Summerville technically pencils out, but only past the point the equipment would need replacing anyway. $5,500 is what Summerville would pay extra to go electric rather than replace the furnace and AC with the same again. Summerville's residents would see roughly $249 a year back in running costs, putting the payback around 22 years. Summerville's own numbers say this pencils out only in theory, not in practice.
Compare against another city
This runs the same numbers for 3206 US cities, not just Summerville. Look one up here.
Why Summerville's climate drives this number
1792 heating degree days pile up here every year, so Summerville has a mild winter by US standards; the cooling side runs to 2226 cooling degree days, where summers are hot enough that cooling matters as much as heating. Sizing runs off the design temperature, not the average day: 23°F here (coldest 2024 reading 21.2°F), which works out to a seasonal COP of 3.25 for the cold-climate class of unit this climate calls for. The average winter here is gentle, but sizing follows the cold snaps, and 23°F is below the 25°F point where a standard unit leans on resistance backup, so a cold-climate unit is what gets priced for Summerville. Source: NOAA station Summerville Airport, 7 miles from Summerville, the closest one on record.
The yearly running costs in Summerville
Modelled on a typical 2000-square-foot house, the heat pump draws about 1,396 kWh a year to keep it warm, plus cooling, for a combined electric bill near $532 a year. The gas furnace it replaces burns roughly 19 Mcf a year at $16.91 per Mcf here, for a running cost near $782 a year including the old AC (electricity here runs 16.16¢/kWh). If the current system still worked and you replaced it anyway, the full cost would take longer than the 15-year equipment life to earn back; against buying a new furnace and AC regardless, the 15-year total lands $1,758 behind.
How sensitive Summerville's result is to prices
This result holds unless electricity climbs above 77.1¢/kWh (it is 16.16¢ now) or gas drops below $3.54 per Mcf (now $16.91); past either point, gas becomes the cheaper fuel in Summerville. When quotes arrive, compare the heat pump price with a like-for-like furnace and AC replacement: at $249 a year saved, a difference under $1,743 pays back within 7 years here, and under $2,490 within 10.
The other scenario: no gas furnace to begin with
Not every home in Summerville has gas service. Compared with baseboard or electric-furnace resistance heat, the numbers shift in the heat pump’s favor. About $667 a year comes back this way, enough that the 15-year payback clears the $10,000 premium comfortably within the equipment's life.
How Summerville compares nationally
Ranked against the other 3206 cities covered, Summerville comes in at 2545 for heating severity, 1 would be the coldest place in the dataset, and 774 by population, where 1 is largest. That's the mildest third of cities covered, where utility rates carry more of the answer than climate does.
Deciding what's next in Summerville, SC
About 52,625 people live in Summerville, South Carolina, and every number on this page is what a contractor would actually work from when quoting a system here, the point isn't to replace that quote, it's to tell you whether to bother asking for one. Here, there's no cost penalty to waiting until your current furnace or AC actually needs replacing.
Get quotes from local HVAC contractors before deciding.
Where Summerville's figure comes from
The methodology guide walks through exactly how Summerville's 3.25 seasonal COP and the rest of this page's numbers get built. At a 23°F design temperature, Summerville sits in cold-climate territory; the guide to that class of unit explains why.