The feasibility of those has pretty much been debunked, evidenced by their hardly ever being advertised in my large metro area anymore.
I've even had plumbers who sell them steer me away from them. And they ARE expensive.
Depends upon your groundwater temps I suppose, they’re going strong in residential here. Going strong in RV’s too, much less power draw plus the space for the tank is freed up for storage or other use, both of which are big pluses in an RV, especially one set up for dry camping without utility hookups.
The newer (2014) Water heaters are very well insulated now. (+3”) The only stupid requirement is basically anything over 55 gals has to be a heat pump type unit.
The tank-less can be quite problematic especially with mineral issues in the water.
To try to run one on electricity is just insane. 60 Amp supply run to the tank-less.
I see some companies are even putting small tanks for storage on their tank-less heaters. Thus coming full circle again.