Instructables

How to make a dishwasher energy saver

Picture of How to make a dishwasher energy saver
In Oslo Norway they have built an heat recovery plant attached to
their sewage treatment plant.   In our houses we heat hot water
only to flush most of this hot water down the drain.   A dishwasher
will heat the water it uses (6 to 10 gallons) to 140-150F.   Since
there are about 8 pounds of water per gallon, this is 8*10*(150-70)
or about 6400 BTU per dishwashing cycle.   This is about 1/20 th
of the energy in one gallon of heating oil or 1/16 of a therm of
natural gas.  And given that your furnace may not be highly efficient,
this could mean that the it represents more saving than that.   So
if during the winter months, you use your dishwasher once every
3 days, you could save a couple of gallons of heating oil or few therms
of natural gas if you could recover all the heat used by your
dishwasher.    Not a whole lot--   but if all 40 million dishwashers in the
USA had heat recovery you could recover 80 million gallons of heating
oil equivalent per year!   Worth more than $200 million dollars!

 
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Step 1: Assemble the downspout

Picture of Assemble the downspout
I am using 2 6 gallon plastic water jugs that I bought at K-Mart.
The dishwasher uses between 6 and 12 gallons depending on
the wash settings.   Splitting this between two water containers
makes it easier to move them around.   The  plumbing connection
for this is made with 1 inch PVC fittings.    One T and 2 right angle
turns are needed with short pieces (4-5 inch) of one inch wide PVC
coming out from the side of the T and connecting the right angle
segment.   Water coming out of the dishwasher  is fed into one
end of the tee and comes out the two sides and into the water
containers.

You could also use that water to flush the toilet saving the perfectly good water for other uses.
pedleyfigg4 years ago
Every bit counts when trying to live greener. Much cheaper than solar panels and useful in any environment. An expansion on hot water bottles. Brilliant idea that I will be installing in my touring caravan when the weather here gets chillier.
theRIAA4 years ago
"but if all 40 million dishwashers in the
USA had heat recovery you could recover 80 million gallons of heating
oil equivalent per year!   Worth more than $200 million dollars!"

So this saves $2.50+/yr per dishwasher? ...how much did all that stuff cost?
jtlien (author)  theRIAA4 years ago
$5 bucks for the pvc.  I think it was about each $8 for the water containers.
BUT... You can use the water containers all summer for camping etc.
The payback would be in about 4 years.   Probably much better than the
return for wind or solar panels.  Next would be to recover the heat from
the washing machine and the shower...  Maybe my math was wrong.
A couple gallons/oil per year = $5-$6 dollars by the time you figure in tax
and furnace inefficiency.    More if you wash dishes everyday like some folks
do.