stretch wrote:

Nick wrote:

I measured a new efficient dehumidifier, which produced 1.6 kWh of heat
for every kWh consumed, ie 1 kWh from motors plus 0.6 kWh to condense
about 2 pints of water, ie it consumed 0.5 kWh per pound of water, ie
5 cents/pint at 10 cents/kWh.

How can a dehumidifier produce mor heat than the equivalent of the
electricity it uses.

It's an indoor heat pump that converts latent to sensible heat,
with a COP of 1.6, in the case above.

A heat pump does that because it extracts heat from outside.

Not always. The dehum above is 60% more efficient than electric resistance
house heating in wintertime. Bill Shurcliff suggests air conditioning damp
basements in wintertime. The AC might be mounted in a stairwell, with the
hot coils in the living space.

...All electricity consumed should be converted to heat.

It is, but beyond that, each pint of water condensed adds about 1000 Btu
of sensible heat to the room air. Evaporating water requires heat energy.
Condensing water releases heat energy.

Nick