Pool swim season in Philadelphia, PA
Swim season in Philadelphia without a heater, and with one
An unheated pool in Philadelphia 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).
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
Heater options for a Philadelphia pool, side by side
| 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 | $133 | $683 |
| Gas heater + cover | 5 | May to Sep | $192 | $617 |
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 Philadelphia
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 Franklin Inst, 4.1 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Philadelphia 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 | 42° | 35° | 1.9 | 36° | 42° | – | – |
| Feb | 45° | 37° | 2.7 | 36° | 42° | – | – |
| Mar | 54° | 45° | 3.6 | 42° | 48° | – | – |
| Apr | 66° | 56° | 4.8 | 52° | 58° | – | – |
| May | 76° | 66° | 5.3 | 63° | 69° | $128 | $185 |
| Jun | 85° | 75° | 5.9 | 74° | 80° | $5 | $7 |
| Jul | 89° | 80° | 6.0 | 81° | 87° | – | – |
| Aug | 87° | 78° | 5.2 | 82° | 88° | – | – |
| Sep | 80° | 72° | 4.2 | 76° | 82° | – | – |
| Oct | 68° | 60° | 2.9 | 66° | 72° | – | – |
| Nov | 56° | 49° | 2.1 | 53° | 59° | – | – |
| Dec | 47° | 40° | 1.6 | 43° | 49° | – | – |
Heating costs most in May (about $128 with a heat pump, $185 with gas). Sunshine peaks in Jul at 6.0 kWh/m²/day (NASA satellite data, 62.8 km grid cell). Highlighted months are swimmable with no heater.
How Philadelphia compares with nearby cities
Philadelphia ranks 1 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 |
|---|---|---|---|---|
| Camden, NJ | 5 mi | 2 | 5 | $145 |
| Collingswood, NJ | 7 mi | 1 | 5 | $252 |
| Gloucester City, NJ | 8 mi | 2 | 5 | $145 |
| Yeadon, PA | 8 mi | 2 | 5 | $169 |
| Lansdowne, PA | 9 mi | 2 | 5 | $169 |
| Darby, PA | 9 mi | 2 | 5 | $169 |