My 50W aquarium heater keeps the water at about 68°F, in
an insulated jug.
A 250W trough heater only keeps water at just above freezing.
Let me explain the different circumstances and wattage differences, and how they act.
Aart's aquarium heater works well, even though LOW wattage comparatively. Reason is the INSULATED CONTAINER. Heater designed to make water @ 68*F. A built in thermostat shuts down power to the heating element when temp reaches setting. Same heater in an open container, and cold ambient temps, like 0*F ,,,,, and result would be possibly FROZEN WATER.
a 250 Watt tank heater is designed to maintain water temperature above freezing temp. Open tank, or insulated container would have similar temps, with the insulated one just slightly higher,,,,,, due to slower heat loss.
Was not able to find the exact temp specs of preset thermostat settings on these farm style Stock tanks. They ALL claim to not overheat water.
Here is a Copy, and paste from one tank's description.
Features
- The patented cast aluminum design is safe, reliable, and efficient and is specifically designed for cold climates
- It can be used in all styles of tanks - metal, rubber, and plastic - without the need for an additional cage or guard
- Best for use in tank sizes of 150 to 300 gallons
- It is thermostatically controlled to turn on and off automatically
- Has a large diameter heating element that is open in the middle to improve the circulation of heat
- The cord is protected by a metal spring which serves to deter chewing
Larger wattage tank heaters will keep a reasonable size tank from freezing.
Farmers with large capacity water tanks for their herds may need multiple heaters, depending on amount of water, and outdoor temps.
I understand that a higher watt heater won’t warm the water to a higher temperature. However if you live somewhere that gets -30 at night you’ll need a higher power heater than someone that barely dips below freezing.
Everything depends on the temperature setting of the heater.
The WATTAGE factor is important to compare, when you need to pair up a heater to your quantity of water to be heated.
Larger quantity, and colder temps mean Larger watt requirements.
Tank heaters do come with suggested sizes for water quantity, and outdoor temperature conditions.