Take a look at this thread......
https://ecorenovator.org/forum/showthread.php?t=6711
I haven't installed the device yet so I can't give you any facts, other than reports from people who have one and are satisfied. One thing is certain, a solar panel and this device is much less headache than hydronic solar collectors. It is probably less expensive as well. Best of all, it won't freeze and break. It is immune to variations in outside temperatures.