Pool swim season in Sumter, SC
Swim season in Sumter without a heater, and with one
An unheated pool in Sumter reaches 78°F in Jul to Aug, about 2 months a year. The air allows up to 7 swimmable months with a heater (Apr to Oct).
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Heater options for a Sumter pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 2 | Jul to Aug | $0 | $0 |
| Solar cover only | 4 | Jun to Sep | $0 | $50 |
| Solar panels + cover | 6 | May to Oct | $0 | $283 |
| Heat pump + cover | 7 | Apr to Oct | $218 | $768 |
| Gas heater + cover | 7 | Apr to Oct | $456 | $881 |
For a 450 sq ft pool held at 80°F, at SC prices of 15.9¢/kWh electricity and $17/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Sumter
Solar panels + cover: 6 of 7 possible months for about $283 a year all-in, which works out near $71 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 2 months here for about $50 a year (why a cover comes first). If you get quotes, ask for a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Sumter, 2.8 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Sumter month by month: air, sun and pool water
| Month | Air high | Air avg | Sun kWh/m²/day | Water, unheated | Water, covered | Heat pump $ | Gas $ |
|---|---|---|---|---|---|---|---|
| Jan | 55° | 44° | 2.9 | 45° | 51° | – | – |
| Feb | 59° | 47° | 3.5 | 46° | 52° | – | – |
| Mar | 66° | 54° | 4.5 | 52° | 58° | – | – |
| Apr | 75° | 62° | 5.8 | 61° | 67° | $127 | $260 |
| May | 81° | 70° | 6.2 | 69° | 75° | $43 | $96 |
| Jun | 87° | 77° | 6.4 | 76° | 82° | – | – |
| Jul | 90° | 80° | 6.2 | 82° | 88° | – | – |
| Aug | 89° | 79° | 5.6 | 82° | 88° | – | – |
| Sep | 83° | 73° | 4.8 | 78° | 84° | – | – |
| Oct | 74° | 63° | 4.0 | 69° | 75° | $48 | $100 |
| Nov | 65° | 52° | 3.1 | 58° | 64° | – | – |
| Dec | 57° | 46° | 2.6 | 49° | 55° | – | – |
Heating costs most in Apr (about $127 with a heat pump, $260 with gas). Sunshine peaks in Jun at 6.4 kWh/m²/day (NASA satellite data, 50.0 km grid cell). Highlighted months are swimmable with no heater.
How Sumter compares with nearby cities
Sumter ranks 30 of 42 South Carolina cities for unheated swim months; Columbia, Forest Acres, Cayce nearby get a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Columbia, SC | 30 mi | 4 | 7 | $180 |
| Forest Acres, SC | 34 mi | 4 | 8 | $258 |
| Cayce, SC | 37 mi | 4 | 8 | $254 |
| Florence, SC | 38 mi | 4 | 7 | $148 |
| West Columbia, SC | 40 mi | 4 | 7 | $153 |
| Orangeburg, SC | 41 mi | 4 | 8 | $301 |