Heat Pump or "hybrid" waters heaters cost quite a bit more than traditional water heaters with the promise that they will save money on your electric bill eventually paying for themselves.

The problem is that even when you follow the manual and properly maintain the filter you will eventually need to call in for service to have the heat exchanger cleaned out. For a DIY person who is not concerned with warranty this will not be a problem but for the majority of people this drawback is unacceptable. The cost to call a service person will wipe out all the savings.

Worse yet, unless you regularly check on your water heater you may not even be aware the the heat pump has stopped working and had fallen back on the heating elements making the water heater a very expensive electric heater.

It is true you can add a filter on top of the unit but this is not told to anyone at the time of sale.