Technically – yes you can add solar to another electric tank, however some things to consider are:

  1. Your warranty may be void on the tank and/or the solar collector.
  2. You will need to purchase extra “retro-fit” valves
  3. The efficiency of the system will be lower as the components have not been designed to complement each other.
  4. You will not qualify for any solar incentives
  5. How long will your existing tank last? And what will the costs be in the future to change it?