hey matt. 

im not 100% sure if there is a difference but i do know that my AC element way to many watts going out.  This is the unit i purchased.  https://globalsolarsupply.com/product/diversion-load-water-heating-element-60a12v-30a24v/

it will work for 12 or 24 volt.  I think if you goole the type of water heater you have you can find out the size of the element.   You will most likely need the professional tool to remove the water heater element.  The cheap home ones will simply not do the job.  at least on my tank that was the case.  ...What brand of water heater do you have?