Pool swim season in Darby, PA
Darby, PA: how long the pool season really is
An unheated pool in Darby reaches 78°F in Jul to Aug, about 2 months a year. The air allows up to 5 swimmable months with a heater (May to Sep).
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What each heater buys you in Darby
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 2 | Jul to Aug | $0 | $0 |
| Solar cover only | 4 | Jun to Sep | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 5 | May to Sep | $169 | $719 |
| Gas heater + cover | 5 | May to Sep | $244 | $669 |
For a 450 sq ft pool held at 80°F, at PA prices of 21.1¢/kWh electricity and $15/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Darby
Solar cover only: 4 of 5 possible months for about $50 a year all-in, which works out near $25 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: Phila International Airport, 3.8 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Darby 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 | 41° | 34° | 2.0 | 35° | 41° | – | – |
| Feb | 44° | 36° | 2.9 | 35° | 41° | – | – |
| Mar | 53° | 44° | 3.8 | 41° | 47° | – | – |
| Apr | 65° | 55° | 5.0 | 51° | 57° | – | – |
| May | 74° | 64° | 5.6 | 62° | 68° | $148 | $210 |
| Jun | 83° | 74° | 6.2 | 72° | 78° | $21 | $34 |
| Jul | 88° | 79° | 6.2 | 79° | 85° | – | – |
| Aug | 86° | 77° | 5.4 | 80° | 86° | – | – |
| Sep | 79° | 70° | 4.4 | 75° | 81° | – | – |
| Oct | 67° | 58° | 3.2 | 64° | 70° | – | – |
| Nov | 56° | 47° | 2.3 | 52° | 58° | – | – |
| Dec | 46° | 39° | 1.8 | 42° | 48° | – | – |
Heating costs most in May (about $148 with a heat pump, $210 with gas). Sunshine peaks in Jun at 6.2 kWh/m²/day (NASA satellite data, 51.1 km grid cell). Highlighted months are swimmable with no heater.
How Darby compares with nearby cities
Darby ranks 5 of 68 Pennsylvania cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Yeadon, PA | 1 mi | 2 | 5 | $169 |
| Lansdowne, PA | 2 mi | 2 | 5 | $169 |
| Chester, PA | 8 mi | 2 | 5 | $151 |
| Gloucester City, NJ | 8 mi | 2 | 5 | $145 |
| Woodbury, NJ | 8 mi | 2 | 5 | $193 |
| Camden, NJ | 8 mi | 2 | 5 | $145 |