[Greenbuilding] Opinions on electric tankless HW heaters?

Wed Apr 20 13:27:25 CDT 2011

Depending on the source of generation, heat pump water heaters have roughly
the same carbon footprint as gas water heater.  However if you power using
electricity from renewables (wind) HPWH is significantly better. My local
utility offers the wind option, so I went with the HPWH with solar preheat.
 Even if one were to use a Drain heat recovery, HPWH is still the best
alternative.

Having said that, demand reduction still comes first.

---- Steve (KZ6LSD)

On Wed, Apr 20, 2011 at 11:04 AM, Frank Tettemer <frank at livingsol.com>wrote:

> 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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