Here's one I found that claims to be 40% cheaper than conventional doors.
Slight problem, they are based in Southern California.
To understand the concept of heat pumps, imagine a refrigerator working in reverse. While a refrigerator removes heat from an enclosed box and expels that heat to the surrounding air, a HPWH takes the heat from surrounding air and transfers it to water in an enclosed tank.
During periods of high hot water demand, HPWHs switch to standard electric resistance heat (hence they are often referred to as “hybrid” hot water heaters) automatically.
While it looks like it'll cost 5x the price of traditional water heaters, we could recoup the investment cost within 5 years.