Pool swim season in Nashua, NH
Nashua, NH: how long the pool season really is
An unheated pool in Nashua never reaches 78°F in a normal year. It peaks around 75°F in Aug. The air allows up to 4 swimmable months with a heater (Jun to Sep).
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Heater options for a Nashua pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 2 | Jul to Aug | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $228 | $778 |
| Gas heater + cover | 4 | Jun to Sep | $320 | $745 |
For a 450 sq ft pool held at 80°F, at NH prices of 26.9¢/kWh electricity and $19/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Nashua
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 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: Nashua Cwsu, 1.1 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Nashua 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 | 35° | 24° | 1.8 | 26° | 32° | – | – |
| Feb | 38° | 27° | 2.7 | 25° | 31° | – | – |
| Mar | 45° | 35° | 3.7 | 31° | 37° | – | – |
| Apr | 58° | 47° | 4.7 | 42° | 48° | – | – |
| May | 69° | 58° | 5.3 | 55° | 61° | – | – |
| Jun | 79° | 67° | 5.7 | 65° | 71° | $132 | $188 |
| Jul | 85° | 73° | 6.0 | 73° | 79° | $12 | $18 |
| Aug | 83° | 71° | 5.3 | 75° | 81° | – | – |
| Sep | 75° | 64° | 4.3 | 69° | 75° | $84 | $114 |
| Oct | 62° | 51° | 2.8 | 57° | 63° | – | – |
| Nov | 51° | 40° | 2.0 | 44° | 50° | – | – |
| Dec | 40° | 30° | 1.5 | 33° | 39° | – | – |
Heating costs most in Jun (about $132 with a heat pump, $188 with gas). Sunshine peaks in Jul at 6.0 kWh/m²/day (NASA satellite data, 27.7 km grid cell). Highlighted months are swimmable with no heater.
How Nashua compares with nearby cities
Nashua ranks 1 of 11 New Hampshire cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Lowell, MA | 11 mi | 0 | 5 | $647 |
| Methuen, MA | 16 mi | 0 | 4 | $196 |
| Manchester, NH | 16 mi | 0 | 4 | $327 |
| Lawrence, MA | 17 mi | 0 | 4 | $196 |
| Fitchburg, MA | 19 mi | 0 | 4 | $380 |
| Haverhill, MA | 21 mi | 0 | 4 | $356 |