A hot-water heat pump can be the cheapest way to heat water at your home or business. When matched with rooftop solar photo-voltaic (PV) electricity generation, hot-water heat pumps save even more.

Operating in a method similar to a reverse-cycle air conditioner in heating mode, a hot-water heat pump uses a refrigerant cycle to heat water by extracting free renewable heat from the air outside your home.

Globally, the International Energy Agency reports that accelerating sales of hot-water heat pumps and has identified these as a renewable-energy technology that is key to slowing climate disruption.

Read more: One step off the grid