Since the sacrificial anode must sacrifice itself to protect the hot water tank, it is important that the anode is large enough to last for several years. More than your water is hard, the less the anode will last. However, the powered anodes rod do not work in the same way, so they are much smaller.
A powered anode related to electricity being fed into the anode to impose a flow of current rather than relying on natural electrolysis. The length and size of the anode, as well as the current sent by the rectifier will influence the life expectancy of the anode. Corro-Protec anodes have been designed to work for more than 40 years, no matter how hard your water is. In order to know more about the lifetime of the current anodes, I invite you to visit our blog post: Tests of Powered Anode