I have this exact model, and I wish I didn't. It turns out there's a flaw in the logic that controls the heating elements. When in "Energy Saver" mode (the default mode), the lower heating element won't heat the water. So when you start to use the hot water, as the hot water goes out, the replacement cold water coming in isn't getting heated at the bottom. This drops the temperature of the existing hot water in the tank, and it takes several hours of no hot water use for the tank to get to your desired temp. For my family it means we get about 1 1/2 showers (showers last about 7 or 8 minutes) before the water starts coming out lukewarm. You can see this happening on your unit by activating the diagnostic mode on the panel and watching the lower element water temp.
I went several rounds with Rheem's customer support (including have two separate techs come to my house to inspect it) before someone finally acknowledged in writing that there's a known defect in the logic of the controller board. They tagged my unit as defective, but so far have not been able to replace it since they haven't engineered a fix and started producing a new version of the water heater with said fix.
My advice, stay away from Rheem hybrid water heaters for a while until they get it sorted out. Also, pro tip: Keep it on the "High Demand" mode so that it's always using electricity + heat pump to heat the water. That gives you the most aggressive heating profile and does not contain the flaw where the lower heater element won't activate. This was the advice their engineer gave me, and it's allowed us to have hot water for more than a shower or two.
I don't have historical data for the initial time period where I was trying to use this "normally" / using the default mode. However, here's a screen shot of last month's usage. Two adults in the house.
I don't get why these need to become complicated enough to become trouble. They've worked very well with just a thermocouple and a gas valve for decades and you'll get 20 years out of one with no issues.
Guessing its a hybrid unit? I have a hybrid one by GE. Goddamn its loud.
Don't forget to turn up the water temperature. Mine also was set to 120 by default, but that's too cold. You need 135-140 or so, otherwise you'll find that you run out of hot water pretty quickly, especially if you have people taking showers back to back, or running the dishwasher/washer while someones showering, etc.
What's an expansion tank? I set it up like the old one was set up. All I did was disconnect the old one and reconnect the new one to the same pipes coming out of the wall.
An expansion tank is necessary for water heaters, because the process of heating water causes it to expand. Without an expansion tank, pressure could build to unsafe levels
I'm not a plumber but that looks pretty clean! Good job. I'm hoping to upgrade to a hybrid electric water heater sometime in the future. Currently running on regular electric (boo!).
Nice job! I have had the same unit for about 3 years now and I have been very happy with it. The amount of electricity it requires compared to a convention is a heck of a lot less. It also has the nice side effect of cooling and dehumidifying my garage during the summer time.
120°F is too low for a water heater. 135°F is the minimum necessary to prevent bacteria growth inside the tank. And like the other person said, your hot water will last a lot longer with a higher temperature. Just don't crank it too far beyond 140° so you don't accidentally burn yourself.