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Electric tankless water heater

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Posted by boustephane on January 12, 2008, 3:23 am
 
Hi,

I have to change my old water heater and plan to buy an electric
tankless water heater (I don't want to use gaz).

We are 5 persons with "normal" needs and we are living in Canada (near
US frontiers). I plan to buy something like "Titan" brand
( www.titanheater.com ) or something else. Maybe I need to combine two
heaters in parallel to raise the capacity ?

I don't need excesive heat. I hesitate to make the change but very
interested by the reduction of electricity  consumption.

Does anyone have experience or comment about this product ?

Thank you !

S.B.

Posted by Paul M. Eldridge on January 12, 2008, 2:43 pm
 
Hi S.B.,

If you live in Ontario, I wouldn't recommend it.  The reason?  All
residential consumers will be shifted to time of use rates, so their
operation during peak times will be especially expensive (i.e., after
7:00 am) -- about three times more costly, in fact.  Secondly, two of
these little puppies would have a combined draw of anywhere from 150
to 180 amps, so unless you have a 400 amp service, it's lights-out,
literally!

As an alternative, I might recommend one (or if need be, two) 60
Imperial gallon conventional DHW tanks controlled by a timer so that
they recharge during off-peak hours [if you find yourself routinely
running out of hot water, you could adjust the timer so that they also
recharge during mid-peak].  In addition, if you can minimize your
overall hot water usage (e.g., front load washer, low-flow shower
heads, etc.) or shift a portion of your consumption to off-peak hours
(e.g., run your dishwasher overnight or do more of your laundry on the
weekends), your potential savings will be greater and you'll less
likely run out of hot water during the more expensive peak times.

Cheers,
Paul

On Fri, 11 Jan 2008 19:23:37 -0800 (PST), boustephane@hotmail.com
wrote:



Posted by boustephane on January 12, 2008, 7:38 pm
 Hi Paul,

Thank you for your answer.  I live in Quebec (near Montreal) and the
rate for electricity is the same all the day. I have a 200 amps
service so I think I have to call an electrician before any move.

Stephane B.

Posted by Paul M. Eldridge on January 12, 2008, 11:38 pm
 Hi Stephane,

My pleasure, indeed.  BobG makes a good point with regards to standby
losses.  In the case of a new, well-insulated hot water tank, these
losses typically fall in the range of 1.5 kWh/day, which works out to
be about 550 kWh/year.

Hydro-Québec currently charges 5.29 cents per kWh for the first 30 kWh
consumed each day and 7.03 cents for any additional energy consumed
thereafter.  If we were to blend these two rates together with the
assumption that your summer demand falls below 30 kWh/day, whereas
your winter demand is generally higher (i.e., your home is
electrically heated), your out-of-pocket expenses would average less
than $.00 per month.

However, if your hot water tank is located within a conditioned space
and your heating season more or less spans October 1st through April
30th, the true cost could be as little as $2.00 per year.

5 months x 30.5 days/month x 1.5 kWh/day = 228.75 kWh/year
228.75 kWh @ $.0529/kWh = $2.10

Here, we used the lower, first tier rate because the losses occur
outside the normal heating season when presumably your demand falls
below 30 kWh/day.  Again, assuming your tank is located inside a
conditioned space, your standby losses during the heating season (and
in Québec I take it that's seven months of year, if not more) simply
offset a portion of your normal space heating requirements -- so your
net cost during these winter months is effectively zero.

With respect to potential issues with legionella bacteria, see:
http://www.hydroquebec.com/advice_hot_water/index.html

Best regards,
Paul

On Sat, 12 Jan 2008 11:38:58 -0800 (PST), boustephane@hotmail.com
wrote:



Posted by nicksanspam on January 17, 2008, 6:14 am
 

That number seems low to me, because I seem to recall that a really well-
insulated tank might have an energy factor (useful hot water output energy
divided by total input energy) of 0.97, which would make the hot water
consumption 1.5/0.03 = 50 kWh/day. IIRC, 50K Btu/day is more typical
for water heating.

And some of the tankless heaters do have small standby losses. They still
keep a small part of themselves warm.

Nick


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