Pool swim season in Derby, KS
Derby, KS: how long the pool season really is
An unheated pool in Derby reaches 78°F in Jul to Aug, about 2 months a year. The air allows up to 6 swimmable months with a heater (May to Oct).
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Heater options for a Derby 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 | 5 | May to Sep | $0 | $283 |
| Heat pump + cover | 6 | May to Oct | $173 | $723 |
| Gas heater + cover | 6 | May to Oct | $324 | $749 |
For a 450 sq ft pool held at 80°F, at KS prices of 15.3¢/kWh electricity and $15/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Derby
Solar panels + cover: 5 of 6 possible months for about $283 a year all-in, which works out near $94 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 a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Haysville 3SE, 4.2 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Derby 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 | 44° | 32° | 2.6 | 33° | 39° | – | – |
| Feb | 48° | 37° | 3.3 | 35° | 41° | – | – |
| Mar | 59° | 46° | 4.4 | 43° | 49° | – | – |
| Apr | 68° | 56° | 5.4 | 54° | 60° | – | – |
| May | 77° | 66° | 6.0 | 64° | 70° | $87 | $171 |
| Jun | 87° | 76° | 6.9 | 75° | 81° | – | – |
| Jul | 92° | 80° | 6.8 | 82° | 88° | – | – |
| Aug | 90° | 79° | 6.0 | 83° | 89° | – | – |
| Sep | 83° | 71° | 5.0 | 77° | 83° | – | – |
| Oct | 72° | 58° | 3.8 | 65° | 71° | $86 | $153 |
| Nov | 57° | 45° | 2.8 | 52° | 58° | – | – |
| Dec | 46° | 35° | 2.2 | 39° | 45° | – | – |
Heating costs most in May (about $87 with a heat pump, $171 with gas). Sunshine peaks in Jun at 6.9 kWh/m²/day (NASA satellite data, 22.5 km grid cell). Highlighted months are swimmable with no heater.
How Derby compares with nearby cities
Derby ranks 12 of 38 Kansas cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Haysville, KS | 5 mi | 2 | 6 | $173 |
| Wichita, KS | 10 mi | 2 | 6 | $168 |
| Andover, KS | 11 mi | 2 | 6 | $169 |
| Bel Aire, KS | 15 mi | 2 | 6 | $169 |
| Winfield, KS | 27 mi | 2 | 6 | $189 |
| El Dorado, KS | 28 mi | 2 | 6 | $178 |