Pool swim season in Butte-Silver Bow, MT
Swim season in Butte-Silver Bow without a heater, and with one
An unheated pool in Butte-Silver Bow never reaches 78°F in a normal year. It peaks around 66°F in Aug. The air allows up to 3 swimmable months with a heater (Jun to Aug).
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Heater options for a Butte-Silver Bow pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 0 | no month | $0 | $50 |
| Solar panels + cover | 2 | Jul to Aug | $0 | $283 |
| Heat pump + cover | 3 | Jun to Aug | $329 | $879 |
| Gas heater + cover | 3 | Jun to Aug | $386 | $811 |
For a 450 sq ft pool held at 80°F, at MT prices of 14.1¢/kWh electricity and $9/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Butte-Silver Bow
Solar panels + cover: 2 of 3 possible months for about $283 a year all-in, which works out near $142 for each month it adds.
A solar cover alone adds no swim months here, so if you want a longer season you need a heater (why); still use one at night to hold the heat you pay for. 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: Butte Bert Mooney Airport, 9 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Butte-Silver Bow 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 | 32° | 20° | 1.7 | 18° | 24° | – | – |
| Feb | 35° | 22° | 2.8 | 21° | 27° | – | – |
| Mar | 44° | 32° | 4.0 | 28° | 34° | – | – |
| Apr | 51° | 39° | 5.1 | 37° | 43° | – | – |
| May | 61° | 48° | 5.9 | 46° | 52° | – | – |
| Jun | 70° | 56° | 6.8 | 55° | 61° | $175 | $195 |
| Jul | 81° | 64° | 7.3 | 64° | 70° | $85 | $106 |
| Aug | 80° | 62° | 6.2 | 66° | 72° | $69 | $85 |
| Sep | 69° | 53° | 4.7 | 59° | 65° | – | – |
| Oct | 54° | 41° | 3.0 | 47° | 53° | – | – |
| Nov | 40° | 28° | 1.8 | 33° | 39° | – | – |
| Dec | 31° | 19° | 1.4 | 22° | 28° | – | – |
Heating costs most in Jun (about $175 with a heat pump, $195 with gas). Sunshine peaks in Jul at 7.3 kWh/m²/day (NASA satellite data, 45.8 km grid cell). Highlighted months are swimmable with no heater.
How Butte-Silver Bow compares with nearby cities
Butte-Silver Bow ranks 8 of 8 Montana cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Helena, MT | 57 mi | 0 | 4 | $223 |
| Belgrade, MT | 72 mi | 0 | 4 | $329 |
| Bozeman, MT | 79 mi | 0 | 4 | $336 |
| Missoula, MT | 94 mi | 0 | 4 | $269 |
| Great Falls, MT | 128 mi | 0 | 4 | $220 |
| Rexburg, ID | 149 mi | 0 | 4 | $229 |