Pool swim season in Sierra Madre, CA
Swim season in Sierra Madre without a heater, and with one
An unheated pool in Sierra Madre reaches 78°F in Aug, about 1 month a year. The air allows up to 5 swimmable months with a heater (Jun to Oct).
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What each heater buys you in Sierra Madre
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 1 | Aug | $0 | $0 |
| Solar cover only | 3 | Jul to Sep | $0 | $50 |
| Solar panels + cover | 5 | Jun to Oct | $0 | $283 |
| Heat pump + cover | 5 | Jun to Oct | $227 | $777 |
| Gas heater + cover | 5 | Jun to Oct | $304 | $729 |
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 Sierra Madre
Solar panels + cover: 5 of 5 possible months for about $283 a year all-in, which works out near $71 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: Mt Wilson Cbs, 4.4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Sierra Madre 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 | 56° | 47° | 3.2 | 47° | 53° | – | – |
| Feb | 55° | 46° | 4.0 | 47° | 53° | – | – |
| Mar | 59° | 49° | 5.4 | 50° | 56° | – | – |
| Apr | 63° | 52° | 6.6 | 54° | 60° | – | – |
| May | 70° | 59° | 7.5 | 60° | 66° | – | – |
| Jun | 79° | 68° | 8.1 | 69° | 75° | $99 | $139 |
| Jul | 85° | 74° | 7.9 | 76° | 82° | – | – |
| Aug | 85° | 75° | 7.4 | 79° | 85° | – | – |
| Sep | 81° | 70° | 6.3 | 76° | 82° | – | – |
| Oct | 72° | 62° | 4.8 | 68° | 74° | $128 | $165 |
| Nov | 63° | 53° | 3.6 | 58° | 64° | – | – |
| Dec | 55° | 46° | 2.9 | 49° | 55° | – | – |
Heating costs most in Oct (about $128 with a heat pump, $165 with gas). Sunshine peaks in Jun at 8.1 kWh/m²/day (NASA satellite data, 55.3 km grid cell). Highlighted months are swimmable with no heater.
How Sierra Madre compares with nearby cities
Sierra Madre ranks 189 of 376 California cities for unheated swim months; Arcadia, Temple City, San Marino nearby get a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Arcadia, CA | 3 mi | 3 | 9 | $650 |
| Monrovia, CA | 4 mi | 1 | 5 | $218 |
| Temple City, CA | 5 mi | 3 | 9 | $650 |
| San Marino, CA | 5 mi | 3 | 9 | $657 |
| Pasadena, CA | 5 mi | 3 | 9 | $657 |
| Duarte, CA | 6 mi | 1 | 5 | $218 |