Charleston / Sullivan's Island
Sullivan's Island is about 9 miles from the Census center point for Charleston in a straight line and covers 2.498 square miles of land (Census 2024 Gazetteer internal points and land area, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/, checked 2026-10-19).
Sullivan's Island has 2,087 residents (give or take 346) (ACS 2020-2024 5-year, table B01003, https://data.census.gov/table/ACSDT5Y2024.B01003?g=160XX00US4570090, checked 2026-10-19), about 835 people per square mile.
The quote form takes a ZIP code; for Sullivan's Island that is 29482 (Census 2020 ZCTA to county subdivision and ZCTA to place relationship files, ZIP areas at least 20% inside the town, https://www2.census.gov/geo/docs/maps-data/data/rel2020/zcta520/tab20_zcta520_cousub20_natl.txt and https://www2.census.gov/geo/docs/maps-data/data/rel2020/zcta520/tab20_zcta520_place20_natl.txt, checked 2026-10-19).
Of the 798 occupied homes in Sullivan's Island, 5% heat with natural gas, 0% with heating oil, 81% with electricity and 13% with propane (ACS 2020-2024 5-year, table B25040, https://data.census.gov/table/ACSDT5Y2024.B25040?g=160XX00US4570090, checked 2026-10-19).
Sullivan's Island has about the Charleston County oil share of 0% and 5 points more electric heat than the county's 76% (ACS 2020-2024 5-year, table B25040, https://data.census.gov/table/ACSDT5Y2024.B25040?g=050XX00US45019, checked 2026-10-19).
Electricity already heats 81% of Sullivan's Island homes, ahead of propane at 13%, and a home on electric baseboard sees the biggest bill change from a heat pump because it replaces resistance heat one for one.
The median Sullivan's Island home was built in 1981 (ACS 2020-2024 5-year, table B25035, https://data.census.gov/table/ACSDT5Y2024.B25035?g=160XX00US4570090, checked 2026-10-19) and the median home has 7.6 rooms (ACS 2020-2024 5-year, table B25018, https://data.census.gov/table/ACSDT5Y2024.B25018?g=160XX00US4570090, checked 2026-10-19).
Sullivan's Island has 1,088 housing units, 27% built before 1940 and 49% before 1980, with 26% built in 2000 or later (ACS 2020-2024 5-year, table B25034, https://data.census.gov/table/ACSDT5Y2024.B25034?g=160XX00US4570090, checked 2026-10-19).
Sullivan's Island has 22 points more pre-1940 homes than Charleston County as a whole (5%) and 13 points fewer homes built after 2000 than the county's 39% (ACS 2020-2024 5-year, table B25034, https://data.census.gov/table/ACSDT5Y2024.B25034?g=050XX00US45019, checked 2026-10-19). An older stock means more insulation upgrades before the heat pump goes in.
90% of Sullivan's Island homes are single-family detached, 2% are in two- to four-unit buildings and 6% are in buildings of five or more units (ACS 2020-2024 5-year, table B25024, https://data.census.gov/table/ACSDT5Y2024.B25024?g=160XX00US4570090, checked 2026-10-19).
With 90% detached houses and 2% in small multi-family buildings, a Sullivan's Island quote is usually one or two outdoor units with ducted or ductless heads sized room by room. With 15% of Sullivan's Island homes rented (ACS 2020-2024 5-year, table B25003, https://data.census.gov/table/ACSDT5Y2024.B25003?g=160XX00US4570090, checked 2026-10-19), the landlord signs the quote in many of them.
Sullivan's Island has 32 points more detached houses than Charleston County overall (58%) and 17 points fewer five-plus-unit buildings than the county's 23% (ACS 2020-2024 5-year, table B25024, https://data.census.gov/table/ACSDT5Y2024.B25024?g=050XX00US45019, checked 2026-10-19).
Only 15% of Sullivan's Island homes are rented (ACS 2020-2024 5-year, table B25003, https://data.census.gov/table/ACSDT5Y2024.B25003?g=160XX00US4570090, checked 2026-10-19), so nearly every quote here is the resident talking to the installer directly, and the rebate goes to the person living in the house.
No electric utility is on file for Sullivan's Island on this door yet, so this page does not name one; the name on the bill decides which rebate path applies.
Median household income in Sullivan's Island is $192,813 (ACS 2020-2024 5-year, table B19013, https://data.census.gov/table/ACSDT5Y2024.B19013?g=160XX00US4570090, checked 2026-10-19); many state and utility heat pump rebate programs set higher incentive tiers for income-qualifying households, so the household income on the application, not the town median, decides which level applies.
Heating design temperature: 28F. Source: ENERGY STAR Design Temperature Limit Reference Guide (2019 Edition), Charleston County row, 99% heating, PDF pages 105 to 107 of 141 (Revised 11/11/2020), https://www.energystar.gov/sites/default/files/Design%20Temperature%20Limit%20Reference%20Guide%20(2019%20Ed)%20-%20ENERGY%20STAR%20Single-Family%20New%20Homes_Rev11.pdf, fetched 2026-10-19, 99%.
That 28F figure is the Charleston County cold-day number a Sullivan's Island heat pump is sized against, so ask the installer to show the system's heating output at 28F, not at the milder rating-label temperature.
Ask for the heat-loss calculation room by room; the median Sullivan's Island home has 7.6 rooms and was built around 1981, and the count of heads and the tonnage follow the rooms and the insulation, not the square footage.
The form on this page is the follow-up for Sullivan's Island. The public number is the number the contractor quotes from.
No local contractor is named on this door for Sullivan's Island yet. A request from this page goes to the first licensed shop that takes the door.