Pool swim season in San Juan, TX
San Juan, TX: how long the pool season really is
An unheated pool in San Juan reaches 78°F in Apr to Oct, about 7 months a year. The air allows up to 12 swimmable months with a heater (all year).
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What each heater buys you in San Juan
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 7 | Apr to Oct | $0 | $0 |
| Solar cover only | 8 | Apr to Nov | $0 | $50 |
| Solar panels + cover | 10 | Feb to Nov | $0 | $283 |
| Heat pump + cover | 12 | all year | $254 | $804 |
| Gas heater + cover | 12 | all year | $618 | $1,043 |
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 Juan
Heat pump + cover: 12 of 12 possible months for about $804 a year all-in, which works out near $161 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 1 month 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: Mcallen Miller International Airport, 5.8 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
San Juan 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 | 73° | 63° | 3.2 | 64° | 70° | $99 | $233 |
| Feb | 77° | 67° | 4.0 | 66° | 72° | $72 | $181 |
| Mar | 83° | 73° | 4.8 | 72° | 78° | $18 | $49 |
| Apr | 88° | 78° | 5.6 | 78° | 84° | – | – |
| May | 93° | 84° | 6.1 | 84° | 90° | – | – |
| Jun | 97° | 88° | 6.9 | 90° | 96° | – | – |
| Jul | 99° | 89° | 6.8 | 92° | 98° | – | – |
| Aug | 100° | 89° | 6.6 | 93° | 99° | – | – |
| Sep | 94° | 85° | 5.4 | 90° | 96° | – | – |
| Oct | 89° | 79° | 4.7 | 84° | 90° | – | – |
| Nov | 80° | 70° | 3.7 | 75° | 81° | – | – |
| Dec | 74° | 64° | 3.0 | 67° | 73° | $65 | $155 |
Heating costs most in Jan (about $99 with a heat pump, $233 with gas). Sunshine peaks in Jun at 6.9 kWh/m²/day (NASA satellite data, 49.0 km grid cell). Highlighted months are swimmable with no heater.
How San Juan compares with nearby cities
San Juan ranks 2 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 |
|---|---|---|---|---|
| Alamo, TX | 2 mi | 7 | 12 | $254 |
| Pharr, TX | 3 mi | 7 | 12 | $254 |
| McAllen, TX | 6 mi | 6 | 12 | $351 |
| Donna, TX | 7 mi | 6 | 12 | $349 |
| Hidalgo, TX | 8 mi | 7 | 12 | $254 |
| Edinburg, TX | 9 mi | 6 | 12 | $373 |