Technology

Things to note about these:

• Most models are 220V 30A. If you have an electrical already, you likely have everything you need here. If you have gas, you will need to run 10 AWG or 8 AWG wiring and install a new breaker. Depending on where you live, you'll likely need a permit and have your handy work inspected before putting the water heater to service. If you aren't sure when you'll need 10 AWG over 8 AWG, hire a professional.
• The 120V 15A models are slower at heating water and do so for a smaller volume. These models you can plug right into the wall, but they are usually a bit slower at coming to temperature for the water and for smaller volume. There's a Rheem version that's plug-in and has something like a 80 gallon store. However, it is highly recommended for use only in warm climates and installed outside in a small enclosure. Basically if you don't live in Southern California, Texas, Florida and all the states that touch those states in between them, you shouldn't try using this.
• Like all heat pumps, there is an air filter that you need to replace. Usually these devices have apps that will notify you when a filter is needing to be cleaned or replaced.
• Also like all heat pumps, there's a fan motor that will make sound. Luckily, most heat pump water heaters attempt to minimize the sound. That said, it's not zero sound and nobody should be recommending that one of these things be installed in a room adjacent to a bedroom. I mean, this is one of those things that really depends on "how well do you tolerate noise?" But these things will produce a pretty consistent hum.
• The act of cooling the air from these reduces the humidity in the air. So you must drain that water that is produced. I think this is one thing that catches most people off-guard about these. Most water heaters don't have a method for draining water because water around a water heater is usually a bad sign. So you do need to drain off the condensate. You can take a big bucket and collect the water to bail later, but how much water it'll produce is dependent on what the humidity is in your area. If you're in like Florida except something like a hint over a gallon of water per day. But most professional installations will install a drain line for you that leads to the outside, unless you're putting this thing like smack dab in the dead middle of your house and you're on a slab. That would obviously present a slightly higher challenge for that drain line installation.

But all that said, these things are super neato. It's just really important for people to have realistic expectations before installing one.