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How much does it cost to heat a fish tank in Massachusetts?
A heater on a 20-gallon tank in a cool Massachusetts room costs roughly $5–11 a month in winter, and a 55-gallon tank roughly $15–30, if the heater runs a quarter to half the time. That's at the state's average residential electricity price of 30.48 cents per kWh (EIA, August 2026), well above the U.S. average of 18.16 cents.
The table assumes a heater sized at 5 watts per gallon, the usual rule of thumb for a room below 68 °F, and shows the cost for a 30-day month if it runs 25%, 50% or 100% of the time. How often a heater runs depends on how cold the room is, the lid and the tank's size, so these are worked examples, not measurements. Calculated by us on November 3, 2026: watts × share of time running × 720 hours ÷ 1,000 × price per kWh.
Monthly heater cost by tank size
| Tank | Heater (5 W/gal) | Runs 25% of the time | Runs 50% | Runs nonstop (most it can cost) | November–March at 50% |
|---|---|---|---|---|---|
| 10 gal | 50 W | $2.74 | $5.49 | $10.97 | $27 |
| 20 gal | 100 W | $5.49 | $10.97 | $21.95 | $55 |
| 29 gal | 145 W | $7.96 | $15.91 | $31.82 | $80 |
| 40 gal | 200 W | $10.97 | $21.95 | $43.89 | $110 |
| 55 gal | 275 W | $15.09 | $30.18 | $60.35 | $151 |
| 75 gal | 375 W | $20.57 | $41.15 | $82.30 | $206 |
In New Hampshire the average residential price was 27.64 cents per kWh in August 2026, so costs there are about 9% lower. Your own rate is on your electric bill: supply plus delivery, divided by kWh used.
Find your real number
- Plug the heater into a plug-in energy meter for a week in winter and read the kWh. Multiply a week's kWh by about 4.3 for a month, then by your rate.
- A lid cuts heat loss and evaporation; an insulating panel on the back and sides helps a tank by a cold wall.
- Many small tanks cost more to heat than one large one. Fish rooms often heat the room instead of each tank.
- Turning the house thermostat back at night makes the heater work harder then, so size it for the coldest hour. Our winter tank guide covers heater sizing and power cuts.
We breed shrimp, plecos and rare fish in Groton, Massachusetts.
Sources: U.S. EIA, Electric Power Monthly, table 5.6.A (average residential price by state, August 2026); Aquarium Co-Op on heater wattage.
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