# Are larger heaters more efficient than smaller heaters?



## Axelrodi202 (Jul 29, 2008)

I would avoid the larger heater because if it malfunctions then your fish will get cooked pretty quickly.


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## Chulios66 (Jan 3, 2013)

I used a heater rated for a 30g for a 5g and I see no harm to this. I bet it would be the same as a heater rated for 5g though.


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## kclone (Nov 11, 2011)

Because of the larger surface area, they would heat your tank faster, but that would be the biggest benefit. They use more electricity. Also, size would also be an issue with a 10 gallon tank. Larger heaters may not as easily fit and limit where you can place the heater in your tank. I'd go for a 50 watt heater.


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## Tom S (Mar 5, 2013)

A watts is a watt. You'll still be putting the same amount of energy into the tank to keep it at temperature, but with the larger heater you will very quickly bring the tank up to temp, while the smaller heater will take more time. And if something goes wrong the larger heater will cook you fish very quickly.


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## ETK (Jan 25, 2013)

kclone said:


> Because of the larger surface area, they would heat your tank faster, but that would be the biggest benefit. They use more electricity. Also, size would also be an issue with a 10 gallon tank. Larger heaters may not as easily fit and limit where you can place the heater in your tank. I'd go for a 50 watt heater.


I think there may be more to it than surface area. Don't the higher wattage heaters get hotter?

I think the OP's question is still not answered. The higher wattage heaters will spend less time on, but draw more wattage while they are on, so I don't think its obvious which would use more energy per day to maintain temp in a small tank. My hunch is that the higher watt heaters will still require more energy, kind of the way a Corvette uses more gas even when driven like a Prius . . . 

Has anyone tried to measure with an experiment?


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## Tom S (Mar 5, 2013)

You need to convert "X" number of electrical watts to heat in order to hold your your tank at a certain temperature above the surroundings. The smaller heater does it over more time, the larger heater does it faster. Unless one has a more efficient way to convert electrical energy to heat (and they all see to operate in roughly the same manner) you aren't going to see any significant change in the amount of energy used to heat the water.


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## Indychus (Feb 21, 2013)

There is no conversion between watts and heat, because watt is a measure of heat (energy) already.

A watt is one joule per second, with a joule being the passing of one ampere of current through one ohm of resistance per second. A Joule is also (approximately) the amount of energy needed to raise one gram of air by one degree centigrade. By multiplying by water's specific heat, you can obtain the required joules to raise one gram of water by one degree centigrade, which is a calorie. Because the tank requires the same number of calories to reach the target temp regardless of heater size, the same number of joules (and therefor watts) are needed to achieve the target temp. Since watts are measured over time, a larger heater will require less time to reach the target temperature, however will put the same amount of energy into the tank as the smaller heater. In effect, either a large heater or small heater will require the exact same electrical input provided that the method of heating is the same (most aquarium heaters are resistance heaters). You can run as large a heater as can physically fit into your tank with little or no consequence; however too small a heater may never reach the target temp if it can not supply the necessary wattage.


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## gSTiTcH (Feb 21, 2013)

ETK said:


> My hunch is that the higher watt heaters will still require more energy, kind of the way a Corvette uses more gas even when driven like a Prius


Higher wattage heaters will use more energy when ON. A heater is going to pump out more heat at a higher wattage due to the larger element/surface area.

More wattage + bigger element = more BTU.

I see potential problems with using an oversized heater:

1) The larger heater will put out more heat into a concentrated area before water currents can distribute it. This is going to cause much more notable 'hot spots' in the tank - not good for living things.

2) A larger heater will have much shorter cycles, which will wear out the thermostat quicker, increasing the risk of thermostat sticking and failure.

3) The hot spots are likely to cause low current parts of the tank to not reach set temperature. As the water around the heater reaches temperature very quickly, the heater will switch off before the heat is distributed.

To play on your example, putting the Prius motor in the Corvette will not work simply because it's underpowered for the job. Putting the Corvette motor in the Prius is more likely to damage the Prius frame, and certainly will not make it run any more efficiently.

I tend to use the right size tool for the job. Why drive a finishing nail with a sledgehammer? Sure, it's much quicker, but the risk of collateral damage is far too high for my tastes.


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