"Ask This Old House"

Just watched episode of Ask This Old House and saw something I’ve never seen before. Electric water heater costing high electric bill for homeowner. So they install a heat pump separate from the electric w.h. (there are models that have it on top of w.h. as one unit - but not this one) . They removed the lower heating element and replaced it with a pex tubing type fitting that takes the colder lower water out from the tank and sends it thru this external heat pump located right next to the w.h. and it is pumped back into the w.h. after collecting heat from the heat pump, I guess its like a concentric type fitting. The upper element remains in the w.h. as a ‘backup’ if the thermostat is not reading the water as being hot enough, it will kick in. Costs about $800 but save approx. $300 per yr in electric bill - they say. A condensate pump carries away the heating pump condensate.
Has anyone ever seen this before and do you think it will save that much money? Or any comments about it in general. BTW , they asked about sediment clogging up the lower pex tubing , Answer to that was installing the water supply from the w.h. cold line feed above the w.h. and then direct that to the heat pump, thus continuing the ‘hot’ water to the bottom of the w.h. from the heat pump.

I JUST saw this too, very unique idea. I love this show and if I even pick up one bit if info during an episode, I consider it a success.