Pool swim season in Louisville/Jefferson County, KY
When can you swim in an outdoor pool in Louisville/Jefferson County, KY?
An unheated pool in Louisville/Jefferson County reaches 78°F in Jul to Aug, about 2 months a year. The air allows up to 5 swimmable months with a heater (May to Sep).
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What each heater buys you in Louisville/Jefferson County
| 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 | 5 | May to Sep | $81 | $631 |
| Gas heater + cover | 5 | May to Sep | $166 | $591 |
For a 450 sq ft pool held at 80°F, at KY prices of 14.2¢/kWh electricity and $14/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Louisville/Jefferson County
Solar cover only: 4 of 5 possible months for about $50 a year all-in, which works out near $25 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: Louisville NWS Office, 3.5 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Louisville/Jefferson County 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 | 42° | 34° | 1.9 | 35° | 41° | – | – |
| Feb | 47° | 38° | 2.6 | 36° | 42° | – | – |
| Mar | 57° | 47° | 3.7 | 43° | 49° | – | – |
| Apr | 68° | 57° | 5.0 | 54° | 60° | – | – |
| May | 77° | 66° | 5.5 | 64° | 70° | $78 | $160 |
| Jun | 84° | 74° | 6.3 | 74° | 80° | $3 | $6 |
| Jul | 87° | 78° | 6.0 | 79° | 85° | – | – |
| Aug | 87° | 77° | 5.5 | 80° | 86° | – | – |
| Sep | 81° | 70° | 4.6 | 75° | 81° | – | – |
| Oct | 70° | 59° | 3.3 | 65° | 71° | – | – |
| Nov | 57° | 47° | 2.3 | 52° | 58° | – | – |
| Dec | 46° | 38° | 1.7 | 41° | 47° | – | – |
Heating costs most in May (about $78 with a heat pump, $160 with gas). Sunshine peaks in Jun at 6.3 kWh/m²/day (NASA satellite data, 39.4 km grid cell). Highlighted months are swimmable with no heater.
How Louisville/Jefferson County compares with nearby cities
Louisville/Jefferson County ranks 12 of 42 Kentucky cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Jeffersontown, KY | 5 mi | 2 | 5 | $70 |
| St. Matthews, KY | 6 mi | 2 | 5 | $70 |
| Lyndon, KY | 7 mi | 2 | 5 | $70 |
| Shively, KY | 9 mi | 2 | 6 | $127 |
| Mount Washington, KY | 10 mi | 2 | 5 | $81 |
| Jeffersonville, IN | 12 mi | 2 | 6 | $165 |