TLDR: Overall, this is a great product, but it's not without faults. I finally got this thing installed and running, but ran into several issues. First and foremost, almost every single water heater uses a 3/4" connection. This unit requires you to downsize to 1/2" out of the water heater (although it does come with the correct piece to do it). The installation would have been a snap had I been able to simply disconnect my 3/4" flex hose, mount this to the water heater, then connect my flex pipe back to the outlet of the booster unit. But, instead I had to purchase additional components at the hardware store to make the connection. Once that was done, I connected the wiring up, and let it go. It worked great, until my circuit breaker tripped, and left me with cold showers the next morning. I reset the breaker, and ran some tests on the unit. I found that whenever it would hit 100% power usage (PWM) for any lengthy period of time, my 30A circuit would trip, every time. I was using 10/2 wire as suggested. I thought my breaker could be bad, so I replaced it with a new one, and the same thing happened. Next, I pulled a new 10/2 wire, thinking the old wire might not be sufficient. No luck. I emailed tech support, and got a very quick response. They suggested I upgrade to a 40A circuit, which required running 8/2 wire. So, another trip to the hardware store. I ran the second 8/2 to the booster unit, and skipped the pigtail connection to the water heater, instead, running the water heater direct wired to the 10/2 30A circuit. (Now my tank and booster can both be on at the same time) Now I'm in business! My water heater pulls 4500 watts from the 30A circuit, and this guy pulls 7200 watts from the 8/2 40A circuit. (theoretically... I haven't put a meter on it to test actual power consumption) In winter, my incoming water temperature is fairly cold... 47F. So, before installing this booster unit, I'd never have a warm shower after my 3 boys took their turns. So far, it seems to be helping out quite a bit, and I'd say everything is a success. In my testing, I was able to see a 30 degree temperature rise with a flow of 1GPM. At 2GPM, I'm seeing about a 15 degree rise. This does not quite match up with what I expected to see...but it does keep my shower usable. Also, I've noted that when the unit is off (not boosting heat), the outlet temperature always reads about 2 or 3 degrees lower than the inlet temperature, while water is flowing. It seems the calibration of the two temperature sensors is not quite right... but 2 degrees isn't such a huge amount that I am too concerned. If you need to pull a new circuit for this unit, I'd suggest starting with 8/2 @ 40A, and skipping the 10/2...
