Pool swim season in Swansea, IL
Swansea, IL: how long the pool season really is
An unheated pool in Swansea 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 Swansea 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 | 5 | May to Sep | $0 | $283 |
| Heat pump + cover | 7 | Apr to Oct | $425 | $975 |
| Gas heater + cover | 7 | Apr to Oct | $469 | $894 |
For a 450 sq ft pool held at 80°F, at IL prices of 19.2¢/kWh electricity and $11/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Swansea
Gas heater + cover: 7 of 7 possible months for about $894 a year all-in, which works out near $179 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 gas as well as a heat pump: once the purchase price is counted, gas comes out cheaper all-in here (heat pump or gas).
Weather station: Belleville Siu Research, 7.9 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Swansea 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 | 43° | 34° | 2.1 | 35° | 41° | – | – |
| Feb | 49° | 38° | 2.8 | 36° | 42° | – | – |
| Mar | 59° | 48° | 3.8 | 44° | 50° | – | – |
| Apr | 71° | 58° | 5.0 | 55° | 61° | $231 | $247 |
| May | 79° | 68° | 5.6 | 66° | 72° | $90 | $109 |
| Jun | 87° | 76° | 6.5 | 75° | 81° | – | – |
| Jul | 90° | 79° | 6.3 | 81° | 87° | – | – |
| Aug | 89° | 77° | 5.7 | 81° | 87° | – | – |
| Sep | 83° | 70° | 4.8 | 75° | 81° | – | – |
| Oct | 73° | 60° | 3.4 | 65° | 71° | $104 | $113 |
| Nov | 58° | 48° | 2.4 | 53° | 59° | – | – |
| Dec | 46° | 37° | 1.8 | 41° | 47° | – | – |
Heating costs most in Apr (about $231 with a heat pump, $247 with gas). Sunshine peaks in Jun at 6.5 kWh/m²/day (NASA satellite data, 42.8 km grid cell). Highlighted months are swimmable with no heater.
How Swansea compares with nearby cities
Swansea ranks 4 of 225 Illinois cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Belleville, IL | 2 mi | 2 | 7 | $425 |
| Fairview Heights, IL | 3 mi | 2 | 5 | $107 |
| Shiloh, IL | 4 mi | 2 | 7 | $425 |
| O'Fallon, IL | 5 mi | 2 | 7 | $425 |
| Collinsville, IL | 9 mi | 2 | 5 | $107 |
| East St. Louis, IL | 9 mi | 2 | 5 | $107 |