Pool swim season in San Marcos, TX
Swim season in San Marcos without a heater, and with one
An unheated pool in San Marcos reaches 78°F in Jun to Sep, about 4 months a year. The air allows up to 9 swimmable months with a heater (Mar to Nov).
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Heater options for a San Marcos pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 4 | Jun to Sep | $0 | $0 |
| Solar cover only | 6 | May to Oct | $0 | $50 |
| Solar panels + cover | 7 | Apr to Oct | $0 | $283 |
| Heat pump + cover | 9 | Mar to Nov | $291 | $841 |
| Gas heater + cover | 9 | Mar to Nov | $683 | $1,108 |
For a 450 sq ft pool held at 80°F, at TX prices of 16.0¢/kWh electricity and $19/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in San Marcos
Heat pump + cover: 9 of 9 possible months for about $841 a year all-in, which works out near $168 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: San Marcos, 1 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
San Marcos 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 | 62° | 51° | 3.0 | 51° | 57° | – | – |
| Feb | 67° | 55° | 3.5 | 53° | 59° | – | – |
| Mar | 73° | 61° | 4.5 | 59° | 65° | $143 | $330 |
| Apr | 80° | 68° | 5.3 | 67° | 73° | $62 | $158 |
| May | 86° | 76° | 5.9 | 75° | 81° | – | – |
| Jun | 92° | 82° | 6.7 | 83° | 89° | – | – |
| Jul | 96° | 85° | 6.6 | 87° | 93° | – | – |
| Aug | 97° | 85° | 6.3 | 88° | 94° | – | – |
| Sep | 91° | 80° | 5.2 | 85° | 91° | – | – |
| Oct | 82° | 70° | 4.4 | 76° | 82° | – | – |
| Nov | 72° | 60° | 3.3 | 65° | 71° | $86 | $195 |
| Dec | 64° | 52° | 2.7 | 56° | 62° | – | – |
Heating costs most in Mar (about $143 with a heat pump, $330 with gas). Sunshine peaks in Jun at 6.7 kWh/m²/day (NASA satellite data, 59.2 km grid cell). Highlighted months are swimmable with no heater.
How San Marcos compares with nearby cities
San Marcos ranks 96 of 252 Texas cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Kyle, TX | 9 mi | 4 | 9 | $291 |
| Buda, TX | 15 mi | 4 | 9 | $339 |
| Lockhart, TX | 15 mi | 4 | 9 | $264 |
| New Braunfels, TX | 16 mi | 4 | 9 | $341 |
| Seguin, TX | 20 mi | 4 | 9 | $246 |
| Dripping Springs, TX | 24 mi | 4 | 8 | $216 |