How does heat pump work? You ask. 

A heat pump works like an air conditioning unit in reverse. It extracts heat from the ambient air surrounding it, enabling it to heat the refrigerant which is then compressed causing it to get even hotter. This is then run through a heat exchanger in which the water is heated.

A heat pump can be retro-fitted onto an existing geyser, which makes for a savvy financial decision. 

Here are few recently completed heat pump installations: