Ok last summer we bought a new to us home. The water heater was original and needed replacing after 22 years.
I replaced it with a REEM heat pump unit in the same spot in the garage. Took a bit longer than normal unit to install (I have install a dozen over the years). It is a DIY. I opted to use PEX to connect to the house CPVC. Also added the now required expansion tank.
When running it not only cools the garage a bit but it also dehumidifies! It does feel more comfortable but by no means AC level comfortable.
I did the math $1600 unit plus $130 in piping. Vs 900 for a higher end regular electric water heater (no gas available) also there was a 1/3 tax credit last year on the price of the unit. So price difference was 2-3 hundred.
As to the cost to run - the REEM keeps track of how many kwts it uses. Efficiency of using heat pump is 2 to 3 times more efficient. So at half the cost, saving about $6 a month. So $72 a year. Payback about 4 years. (I am using the heat pump only heating option unless we have overnight guests then I use quick recovery which uses both heat pump and traditional resistance rods)
BUT the biggest benefit is a “free” dehumidifier. I have not measured the exact drop vs outside (will depend how many times you open the garage door) but can say it is definitely less.
One last point- there is a condensation drain you will have to find a place for. I had a slop sink in the same area I am using. I love to see all the water that comes out!
No I do not work for REEM or any plumber. And I do NOT hire out (you can’t afford me anyway
uTube videos available to see how they work and how to install.