Pool swim season in Key Biscayne, FL
Key Biscayne, FL: how long the pool season really is
An unheated pool in Key Biscayne reaches 78°F in Apr to Nov, about 8 months a year. The air allows up to 12 swimmable months with a heater (all year).
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Heater options for a Key Biscayne pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 8 | Apr to Nov | $0 | $0 |
| Solar cover only | 12 | all year | $0 | $50 |
| Solar panels + cover | 12 | all year | $0 | $283 |
| Heat pump + cover | 12 | all year | $28 | $578 |
| Gas heater + cover | 12 | all year | $100 | $525 |
For a 450 sq ft pool held at 80°F, at FL prices of 15.3¢/kWh electricity and $25/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Key Biscayne
Solar cover only: 12 of 12 possible months for about $50 a year all-in, which works out near $13 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 4 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: Cape Florida, 1.4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Key Biscayne 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 | 78° | 70° | 3.7 | 72° | 78° | $15 | $53 |
| Feb | 79° | 72° | 4.5 | 72° | 78° | $13 | $47 |
| Mar | 81° | 74° | 5.5 | 75° | 81° | – | – |
| Apr | 84° | 78° | 6.2 | 79° | 85° | – | – |
| May | 87° | 81° | 6.2 | 82° | 88° | – | – |
| Jun | 90° | 84° | 5.7 | 85° | 91° | – | – |
| Jul | 91° | 85° | 5.9 | 87° | 93° | – | – |
| Aug | 91° | 85° | 5.6 | 88° | 94° | – | – |
| Sep | 90° | 85° | 5.0 | 87° | 93° | – | – |
| Oct | 87° | 82° | 4.5 | 85° | 91° | – | – |
| Nov | 83° | 77° | 3.9 | 80° | 86° | – | – |
| Dec | 80° | 73° | 3.4 | 75° | 81° | – | – |
Heating costs most in Jan (about $15 with a heat pump, $53 with gas). Sunshine peaks in May at 6.2 kWh/m²/day (NASA satellite data, 39.7 km grid cell). Highlighted months are swimmable with no heater.
How Key Biscayne compares with nearby cities
Key Biscayne ranks 2 of 173 Florida cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Coral Gables, FL | 6 mi | 7 | 12 | $47 |
| Miami, FL | 6 mi | 6 | 12 | $99 |
| South Miami, FL | 8 mi | 7 | 12 | $47 |
| Miami Beach, FL | 8 mi | 6 | 12 | $99 |
| Pinecrest, FL | 9 mi | 7 | 12 | $47 |
| Palmetto Bay, FL | 11 mi | 7 | 12 | $47 |