It is usually taken as axiomatic that electric, resistive heaters are not desirable on a
cruising sailboat. This is especially true if you do not have a generator that you run on
a regular basis. Arguments such as "pennies a day" are meaningless when you're off the
grid.

Looking at the numbers for this unit, the standby power is 75 Watts for 42 minutes. This
translates into about 5 Amp-Hours at 12 Volts. This doesn't sound like a lot, but if
you're charging by running the engine, this is roughly an extra 5 minutes of engine
running a day. This is aside from any power you might get from solar, etc, and holds true
if you end up needing an engine run every day. Further, using it will require another 2
or 3 minutes of engine run.

There is another hidden cost: since this requires AC power you'll have to run an inverter
full time. If you use a small one the efficiency might be as high as 85% (add another
Amp-Hour), and the standby current is 0.1 Amp (add 2.4 Amp-Hours per day).

The net result is roughly 10-12 Amp-Hours, which for an average sized battery bank, means
about 10 minutes of charge time. Every day. And what have we gained? You could used the
preheated water for coffee, but the 190 (cooled to 180 by the time it hits the coffee)
degrees is actually not quite hot enough so you'd end up heating on the stove for a few
seconds. I boil a quart of quart for coffee in roughly the time its takes to grind the
beans. I don't know how much one minute of propane costs, but I suppose you could say
that I had to refill my tank a day early because of it. (Actually it probably doesn't
affect the frequency of refills at all, since I use less than a tank for a simple season.)

Actually, you could probably use a microwave for hot water, with roughly the same
electrical cost.

BTW, I have an "Instant Hot" at home, and it comes in handy when I want it, but its never
occurred to me to have one on the boat.

This is all assuming the purpose is to get near-boiling water. If what you really want to
do is wash your hands, a basic hot water tank can be easily plumbed that will provide 6-12
gallons of hot water as a by-product of running your engine for 20 minutes. It can also
by run with dockside AC power.

-jeff



"Conor Crowley" wrote in message
om...
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).