Heat pumps, geothermal and AC
Increased efficiency with heat pumps working in tandem
...heater that offers you only a 1 to 1 ratio. The Voltex water heater from AO Smith is an air-to-water heat pump which extracts heat from the air to generate hot water, so in the winter that 3 to 1 heating ratio of the first heat pump is transferred to the water heater.
And the more 'free' heat you have in winter (solar ...