DC Water Heating Elements – Real World Examples

We get asked all the time about DC water heating either with just the use of solar panels or solar panels with the use of a battery.  People want to keep stock tanks from freezing or convert their AC water heater to a DC model.  That’s achievable, it’s just about managing the expectation of how many watts it’ll really take to heat the water.


DC Water Heating Examples

It requires 2.47 watts to heat one gallon of water by one degree in one hour.


In the winter, when most people want to put a DC water heating element to use, you’re looking at 5-6 peak hours of sunlight in a single day.  You’ll have low-light hours for power production, too, but you can’t estimate a half day of full sun in most areas.  So, what does this mean?  Let’s put together a real-world scenario of what solar and DC elements are capable of.

In the examples below, we will use two 100 watt solar panels (200 watts total) and a 12 volt, 200 watt DC water heating element.*  Let’s get started:

Volume Starting Temperature (degrees F) Ending Temperature (degrees F)
5 Gallon Bucket 60 degrees 120 degrees
10 Gallon Tank 60 degrees 95 degrees
100 Gallon Tank 60 degrees 61.25 degrees


Here are some real world examples of what one 260 watt solar panel and one 24 volt, 600 watt DC water heating element can do.*

Volume Starting Temperature (degrees F) Ending Temperature (degrees F)
5 Gallon Bucket 60 degrees 150 degrees
10 Gallon Tank 60 degrees 125 degrees
100 Gallon Tank 60 degrees 62.5 degrees


Now let’s move on to even higher wattages.  This examples uses two 260 watt solar panels and one 48 volt, 700 watt DC water heating element.*

Volume Starting Temperature (degrees F) Ending Temperature (degrees F)
5 Gallon Bucket 60 degrees 235 degrees
10 Gallon Tank 60 degrees 155 degrees
100 Gallon Tank 60 degrees 66 degrees

*This is with air temperature that is average of 60 degrees. You will achieve higher temperatures with a starting temperature above 60 degrees and will not achieve the temperatures stated above at lower than 60 degree temperatures.

Example: if ambient air temperature was 33 degrees, it will make your water temperature fall as well to the point of 33 degrees. It would cause the 100 gallon tank to see barely any perceptible heating results due to this fact.

Not to despair, however.  If you have a large stock tank, you’ll simply require more panels and multiple elements per tank and potentially the addition of a battery or batteries to keep things from freezing.  If the volume of water is significant, 100 gallons and more, and you have extremely frigid temperatures, you might consider the addition or alternate option of aeration!

Where should you position the water heating element?

That’s just as important in getting the result you want as in buying the correct number of panels.

Keep it near the top! Unlike a conventional water heater, you’ll want to position the water heating element close enough to the top to keep a hole melted through the ice.  Do not position it so high where the livestock will drain the water level below the element or it will burn out.  Position it too low and you may never see the positive effects where you need it.


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13 Responses to DC Water Heating Elements – Real World Examples

  1. Raymond Mourrs says:

    I would like to know the orixe please.

  2. Raymond Mourrs says:

    Excuse the typo error.. WANTED TO SAY.. THE PRICE LIST. and If can be delivered to Dominican Republic.

  3. Hank Ethier says:

    Does the wattage of the solar panels have to match the D.C. element wattage exactly? I have two 275 watt solar panels and want to hook directly to the element. No batteries.

    • crystal says:

      The 48v 600 w element is the only one that should be used for solar direct. It has a fixed resistance value like all the other elements do. However most solar panels produce 6-8 amps maximum. 100 watt to 350 watt panels all about 6-8amps. This commonality applied to the “48v” “600 watt” element is ideal. In other words the 48 600 element emulates battery resistance most identically than any other element, only because of their fixed resistive value is too high or too low. Too low and the solar panel voltage crashes to near zero and gives it all of its amps. 1 volt x 8 amps = yup! 8 watts.

  4. Scott says:

    Say I have a 500 gallon heavily insulated tank filled with water that circulates through my garage floor. I want to maintain a water temp of 120-150 degrees. Could this be done using solar panels or wind turbine or combo of both for a reasonable investment?

  5. Andy Li says:

    I have a question. You mentioned for 5 gallon water to raise 10 degree F need 123.5W per hour. With your heat element, can you tell me how long it take to raise 10 degree for 5 gallon. Let’s say we connected to 24V battery.


  6. Aaron says:

    I’m curious about Scott’s question. I want to do something very similar. I have a 400 gal tank for hydronic use. Heat loss should be minimal in the tank and will circulate through a cement floor. So I’m wondering if I can use DC heating elements to heat the water.

  7. Elmer says:

    Hi i have two 255watts panels. I want to convert my 20 galons heater to dc . What i need the thermostat and water heater element. ? I want to connect the solar panels direct no batteries

  8. Keith Bakker says:

    Have 50vgallon water heater I want to hookup to solar panels. Roof facing south in Texas good sunlight. Water to have reasonable hot water for 2 people. What do I need to get. Keith. No batteries

  9. Dennis says:

    Hello are the adjustable DC water heater element ignition protected? Safe to place in a water heater that’s in the engine compartment of a gas boat? Naturally worried about any possible sparks when the element turns on. Thanks

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