It works well for our household of 4 including 3 who tend to prefer long showers. I did two reviews on this unit to provide some real-life measurements for people consider the unit. Just be sure that the unit gets a good supply of inlet water (no extra restrictions) . I would suggest a tank on the inlet side with an air cushion and to consider adding (even temporarily) a simple pressure gauge on the inlet side to test that your plumbing system can keep up with the water supply into the heater.
The other tricky thing is to find a location for the heater and heater exhaust that complies with the natural gas regulations (3 ft from a window /door/etc and to deal with Ottawa snow drifts)

It appears to be gas because the description mentions venting and the use of a burner.

Right from the Rheem Manual for this unit on page 7:

Do not install the water heater in
Recreational Vehicles, Mobile Homes,
Boats and other Watercrafts.

I picked one up at Home Depot.

The vent kit can be special ordered at any of the Home Depot stores. Sometimes the stores carry it but you would have to check which stores have it for special order and which stores have it in-stock. Hope this helps.

120 volts . A minimal power consumption.
It only draws about 2.2 watts on standby and 45 watts when the fan is running.

Hello. I am an HVAC Tech and I would assume that you are correct that you have 1/2 inch water lines in your house. Most older homes do. I have installed tank-less units with 1/2 trunk lines before but I don't usually recommend it. The problem you can have is that the unit cant move enough water and slowly the heat exchanger heats up. This causes the unit to shut off the burner to cool the unit. It usually only takes a couple seconds (maybe 10) for the exchanger to cool down and re-activate the flame. Unfortunately this can be a little shocking if your in the shower. This problem is compounded by todays low flow shower heads. Sometimes this can be solved by adjusting the draft inducer speed to accommodate more exhaust airflow, but not always.
In my professional opinion, I would increase your trunk lines to 3/4 inch or just replace your existing hot water tank with a new model. Call a plumber or HVAC Tech to discuss your options.

Yes the only differance is the propane has a smaller orface for the burner

I installed one in my home.
It uses 88 amps and 21000 watts so, I had to use 2 - double pole 50 amp breakers.
Since the heater was over 10 feet from my panel, I had to use #6 wire, you can use #8 if under 10 feet.
I also had a disconnect box next to the heater.
I also installed ball valves on each side of the heater and a pressure relief valve.
Good Luck.

there is an energystar label on the box.