Just installed this. Found it new in the box for $75 on craigslist. Old 20 gallon had been leaking all summer. This is running on my 300W inverter board power point controller. According to box it takes 888WH to raise 6 gallons 60 degrees. Pretty easy to do with 2-3 hours of good sun. It uses the existing thermostat to switch the 60V from the panels so no additional temp controller is needed. It says 50-140F, but it switches off at 124F, probably for legal reasons of scalding. Quite pleased with it as it heats up a lot faster due to being smaller. The other 9 gallon tank operates as a pre heater. Only bad thing is there is no drain for winter. Have to turn it upside down to drain. Hence, washing machine hoses.