The owner of scuba diving school once commented to me on how
astounded he was regarding cost savings after replacing his water
heater with small, individual, point-of-use water heaters in his
shower stalls. For some reason this has always stuck with me, and now
I noticed the following attractive item in the local h/w sto
http://insinkerator.com/pdf/hc1100.PDF

I'm interested in getting some feedback on what the 'gotchas' might be
installing this on cruising sailboat. I suspect 190°F is probably
scalding, but using both the hot and cold together is probably good
enough for hand washing. In terms of power consumption, I contacted
the company and received the response below:

...Conor


Steamin' Hot Water Dispenser…
Energy Consumption Information
(For ½ gallon tanks)

The original ISE Hot Water Dispenser was designed to provide " instant
food temperature water" for the kitchen.
Studies @ the Iowa State University Heat Transfer Laboratory have
shown that when used as an aid in cooking and the preparation of all
"instant foods" the hot water dispenser can save "over 80 percent
normally used in cooking where hot water is required." It also saves
water, since only the water used in cooking, without any waste.

TYPICAL KITCHEN USE & COST
The ½ gallon water tank is fully insulated with expanded polystyrene
foam and uses a 75-watt element to heat the water. It is generally
located under the sink directly below the decorative faucet. An
automatic thermostat maintains the water in the tank @ 190°F, the
ideal preparation of "instant foods".

During normal use (when hot water is drawn from the faucet, colder
water replaces it in the tank) the thermostat will turn the heating
element "on" to maintain the 190°F temperature. The thermostat also
turn the heater on periodically, even when no water is being used, to
replace the heat lost to the air (a water heater does exactly the same
thing.

The cost of heating water in the Hot Water Dispenser is a combination
of two factors: standby cost and dispensing cost. The standby cost
is the power used to maintain the tank temperature even when there is
no water being used. The dispensing cost is the power used to heat
the water actually drawn from the faucet.

The ISE standby cost is 0.52-kilowatt hours per 24 hours. This means
that the heating element is only on 42 minutes for 24 hours.

The ISE dispensing cost is approximately 0.021-kilowatt hours per 8oz
cup of water used.

The average daily usage of the dispenser is about 10-8oz cups.

A typical cost for electricity is about 8 cents per kilowatt-hour.

Standby cost 0.52 x 0.08 = $00.0416 (4
cents)
Dispensing cost 0.21 x 10 x .08 = $00.0168 (less than 2
cents)
THE TOTAL DAILY COST FOR THE DISPENSER IS: $00.0584 (less than 6
cents).