[Greenbuilding] Opinions on electric tankless HW heaters?

Wed Apr 20 13:04:19 CDT 2011

Hi All,

I can't vouch for Nick's idea that they only manufacture 13KW tank-less 
hot water heaters.  I think that the manufacturers would certainly 
provide electric tank-less heaters of all electrical load sizes, simply 
because there would be a demand for lighter-duty models, and Somebody is 
going to fill that market.  However,

That doesn't mean that a light-weight tank-less heater would provide a 
satisfactory supply of hot water.  And certainly anyone who has traveled 
South of the border, to various Carribean countries has experienced 
those light-duty electric shower heaters, plugged into an overhead 
electrical recepticle, just out of reach of the shower curtain.  (I'm 
not promoting these models for US or Can. use, however.)

What I do think is entirely wrong,
is the idea that an electric hot water heater, of any make or model, 
could possibly be considered environmentally friendly.  It's just way 
too big of a stretch in reality.

Consider that a typical household of four would probably spend about $30 
to $40 per month on heating hot water.  Either system, tank-less or tank.
This is equal to about 400 Kwh, at the household's electrical meter base.
This is also equal to about 1,300 Kwh of comparable fuel, being burnt at 
the coal plant, or nuked at the nuke plant.
(As we know, the accumulated losses, from conversion of fuel to heat, 
conversion of heat to steam, conversion of steam to rotary motion, 
conversion of motion to electrical current, and line losses from 
transmission all add up to a factor of about 3.25 to 1.  This is a 
phenomena that is hard to accept, but even more impossible to ignore, 
while designing appropriate technologies in an energy efficient home.

Yes, Carmine, if we only look at the almighty dollar, and compare costs 
of various methods of heating domestic hot water, or heating hot water 
for distribution into household heating, the electric devices all end up 
costing less to purchase and to operate, in the initial assessment.

Giving regard to overall embodied energy of construction of the domestic 
hot water system, and associated energy of electrical production and 
transmission over a decade or two, however, the question arises as to 
how this all pans out over the coming decade or two.  Looking at a 
comparison of economics, via using the dollar as the unit of measure is 
way too short-sighted. It is misleading and hides the truth.

In my humble opinion, and in my home design practice, I have not 
specified any greater electrical use in a home that can be produced near 
to the location of the home.  As well, the PV array and/or wind turbine 
associated with the home's electrical production really must be capped 
at a small enough investment, (both dollars and embodied energy), that 
this system is also not a burden to the planet.  In other words, 
designing a 10KW PV system, plus a 10Kw wind turbine, for one single 
household, is to me a pathetically privileged idea, and un-necessary 
exhibition of wealth, and simply represents a too large footprint.  I 
have built many homes over the years, on of off grid, that operate on 3 
to 5 Kwh per day, total electrical loads, simply to avoid the burden to 
the grid and to the planet in general.

If the average Canadian household uses 29 to 32 Kwh per day, then a home 
that uses only 5 Kwh per day is living more lightly.  And this 
difference, when converted to fuel consumption for the electricity used, 
represents over 2,000 units of fuel equivalency.
This represents a savings upon the grid, and lightens it's load.

Nearly any other fuel will have a lighter impact than electricity for 
hot water.  And I'm not even taking nuke meltdowns, like in Japan, into 
the equation.  If we add that level of environmental toxicity to the 
balance sheet, avoiding electrical on-demand hot water heaters is a no 
brainer.

If we are serious about discussing economic and environmental waste, 
let's first consider simply living with less expectations, way less 
over-all consumption of all goods, accepting and surrendering to the 
uncomfortable fact that this planet cannot support our North American 
"needs" any longer, without these "needs" being clearly labeled as 
privilege and greed.

I believe that it is misleading people with advice that switching from 
one fossil fuel to another is going to "improve" the environment.  There 
is no "better" fossil fuel, just as there is no better way to continue 
to consume goods at the rate of most middle class households.

Our best fuel is a leap of faith around finding that living with way 
less is way better.

Frank Tettemer

Frank Tettemer
Living Sol ~ Building and Design
www.livingsol.com
613 756 3884

.............................................................................................................................................
Nick: Please stop misleading people with your erroneous advice. We all 
know your prejudice against both tank-less heaters & tank-less drain 
water heat recovery systems that can deliver Energy Factors well above 
that offered by the kinds of water heaters you promote.
Carmine
gfxechnology.com

------------------------------------------------------------------------
From: npyner at tig.com.au
To: greenbuilding at lists.bioenergylists.org
Date: Tue, 19 Apr 2011 09:37:24 +1000
Subject: Re: [Greenbuilding] Opinions on electric tankless HW heaters?

Instant electric is usually the last choice on economic and 
environmental grounds.
I doubt that Rheem would make them. Another manufacturer that does is 
Stiebel Eltron. They have some pretty sophisticated models but they are 
expensive and probably no more efficient than their simpler ones.
Even a small instant electric will take about 13kW, so retrofitting one 
may call for some expensive wiring.

Nick Pyner

Dee Why   NSW
-----Original Message-----
*On Behalf Of *Matt

I have clients who might be ideal candidates for a tankless hw heater. 
They don't have natural gas in their home. I have installed gas 
tankless, but don't have any experience with electric tankless heaters. 
I will need to size one for a family of two to four.

Any opinions out there? Bosch? Rinnai? Rheem?...

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