Pool swim season in San Diego, CA
Swim season in San Diego without a heater, and with one
An unheated pool in San Diego never reaches 78°F in a normal year. It peaks around 76°F in Aug. The air allows up to 8 swimmable months with a heater (Apr to Nov).
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Heater options for a San Diego pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 3 | Jul to Sep | $0 | $50 |
| Solar panels + cover | 7 | Apr to Oct | $0 | $283 |
| Heat pump + cover | 8 | Apr to Nov | $699 | $1,249 |
| Gas heater + cover | 8 | Apr to Nov | $931 | $1,356 |
For a 450 sq ft pool held at 80°F, at CA prices of 32.6¢/kWh electricity and $22/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in San Diego
Solar panels + cover: 7 of 8 possible months for about $283 a year all-in, which works out near $40 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 3 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 Diego Montgomery Field, 1.5 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
San Diego 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 | 67° | 57° | 3.2 | 57° | 63° | – | – |
| Feb | 67° | 57° | 4.1 | 58° | 64° | – | – |
| Mar | 69° | 59° | 5.2 | 60° | 66° | – | – |
| Apr | 71° | 62° | 6.1 | 63° | 69° | $208 | $269 |
| May | 72° | 64° | 6.1 | 66° | 72° | $150 | $202 |
| Jun | 75° | 67° | 5.9 | 69° | 75° | $96 | $134 |
| Jul | 80° | 72° | 6.1 | 73° | 79° | $22 | $32 |
| Aug | 82° | 74° | 6.1 | 76° | 82° | – | – |
| Sep | 81° | 73° | 5.4 | 76° | 82° | – | – |
| Oct | 78° | 68° | 4.3 | 72° | 78° | $46 | $65 |
| Nov | 73° | 61° | 3.4 | 65° | 71° | $177 | $229 |
| Dec | 67° | 56° | 2.9 | 59° | 65° | – | – |
Heating costs most in Apr (about $208 with a heat pump, $269 with gas). Sunshine peaks in Apr at 6.1 kWh/m²/day (NASA satellite data, 51.1 km grid cell). Highlighted months are swimmable with no heater.
How San Diego compares with nearby cities
San Diego ranks 236 of 376 California cities for unheated swim months; La Mesa, Santee, El Cajon nearby get a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| La Mesa, CA | 7 mi | 2 | 9 | $834 |
| Santee, CA | 8 mi | 2 | 9 | $716 |
| Lemon Grove, CA | 8 mi | 0 | 6 | $456 |
| El Cajon, CA | 10 mi | 2 | 9 | $716 |
| National City, CA | 11 mi | 0 | 6 | $456 |
| Coronado, CA | 12 mi | 0 | 6 | $412 |