Pool swim season in Gillette, WY
Swim season in Gillette without a heater, and with one
An unheated pool in Gillette never reaches 78°F in a normal year. It peaks around 74°F in Aug. The air allows up to 4 swimmable months with a heater (Jun to Sep).
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What each heater buys you in Gillette
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 1 | Aug | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $166 | $716 |
| Gas heater + cover | 4 | Jun to Sep | $273 | $698 |
For a 450 sq ft pool held at 80°F, at WY prices of 14.0¢/kWh electricity and $12/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Gillette
Solar panels + cover: 4 of 4 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 1 month 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: Gillette 4SE, 2.5 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Gillette 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 | 36° | 26° | 1.8 | 25° | 31° | – | – |
| Feb | 38° | 27° | 2.7 | 26° | 32° | – | – |
| Mar | 49° | 37° | 3.9 | 33° | 39° | – | – |
| Apr | 56° | 44° | 5.0 | 42° | 48° | – | – |
| May | 66° | 53° | 6.0 | 52° | 58° | – | – |
| Jun | 77° | 64° | 7.1 | 63° | 69° | $94 | $155 |
| Jul | 86° | 72° | 7.2 | 72° | 78° | $16 | $29 |
| Aug | 85° | 71° | 6.2 | 74° | 80° | – | – |
| Sep | 75° | 61° | 4.7 | 67° | 73° | $56 | $89 |
| Oct | 59° | 47° | 3.1 | 54° | 60° | – | – |
| Nov | 46° | 35° | 2.1 | 40° | 46° | – | – |
| Dec | 36° | 26° | 1.5 | 29° | 35° | – | – |
Heating costs most in Jun (about $94 with a heat pump, $155 with gas). Sunshine peaks in Jul at 7.2 kWh/m²/day (NASA satellite data, 25.3 km grid cell). Highlighted months are swimmable with no heater.
How Gillette compares with nearby cities
Gillette ranks 2 of 11 Wyoming cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Sheridan, WY | 81 mi | 0 | 4 | $216 |
| Spearfish, SD | 84 mi | 0 | 4 | $198 |
| Casper, WY | 107 mi | 0 | 4 | $151 |
| Rapid City, SD | 114 mi | 0 | 4 | $136 |
| Box Elder, SD | 120 mi | 0 | 4 | $160 |
| Riverton, WY | 168 mi | 0 | 4 | $182 |