On Jun 6, 1:30�am, BoyntonStu wrote:
A 9 KW tankless HWH manufacturer claims that it is sufficient for a
whole house at up to 3 GPM.

A 30 gal short tank HWH is about 30" tall and many are mounted over a
clothes dryer on a shelf.

That got me to thinking:

Size - not too important if hung.

Power - both 9 KW.

Instant hot water: - Tank water is preheated. �The tankless requires
0.5 GPM to begin heating.

Cost - Conventional HWH is cheaper.

Longevity - Tankless is supposed to last twice as long.

Replacement elements - Conventional elements about $15 at Home Depot,
etc.
� � � � � � � � � � � � � � � � � �Tankless elements are not standard
and cost more.

Recovery - �With 9 KW of heating available in both units they may be
equal.
� � � � � � � � (You must use up all the 30 gallons before additional
HW is needed.)

Upgrading: �Conventional elements are available in 5, 5.5, and 6 KW
sizes.
� � � � � � � � � Therefore a 12 KW 30 gallon is doable and it would
heat faster.

Efficiency: �Tankless is slightly more efficient.

Location - �I am in Florida where the input temperature is 70*F.

The main benifit of "tankless" or instantaneous water heaters is that
if you are storing hot water, there is a heat loss and
this can be considerable if you have the heater on 24/7. So a
tankless
is lots more efficient, you heat the water when you need it and the
amount you want. It can easliy save half or threequarters the
energy. However 9kW is OK for basins and showers but you would be
forever trying to fill a bath.
Here in the UK instantaneous showers are very common but 9kW is
at the lower end, you need 12kW for a good shower.
For hand washing there are instantaneous heaters of only 3kW but they
are a spray. The water temperature is controlled by regulating the
amount of water, the heat output is fixed.

For bath filling over here we have special gas boilers that use the
entire output of the house heating boiler to instantaneously heat the
water. Usually start at 24kW (gas) input. Nobody stores water over
here any more, not for years.