Heater Element, Electric Backup, 1500 W : 1500 W backup heater element to fit inside integrated solar system tank, works with any controller If you wish a electric heater element to fit into your solar tank, but not the whole electronic controller-heater package, we can sell you the heater element only. You may just buy the heater part of the heater-controller and get your own thermostat or timer to turn on the backup heat.