[Greenbuilding] Opinions on electric tankless HW heaters?

Wed Apr 20 23:33:16 CDT 2011

Bob
Your strategy would save energy and cost less and certainly in the spirit of
"demand reduction".  It, however, would not pass the spousal acceptance
test.

---- Steve (KZ6LSD)

On Wed, Apr 20, 2011 at 8:36 PM, Bob Waldrop <bwaldrop at cox.net> wrote:

>   I think you can get the same effect, for a lot less money, by simply
> installing a regular tank electric water heater and putting an on-off switch
> on it, and be frugal in your use of hot water.  (We are the masters of the
> three minute shower.)  When  our tank has cooled to ambient, and I flip the
> switch, within about 10 minutes I get a stream of hot water at the tub or
> the kitchen sink.
>
> Bob Waldrop, Okie City
>
>
>  *From:* Steven Tjiang <steve at tjiang.org>
> *Sent:* Wednesday, April 20, 2011 1:27 PM
> *To:* Green Building <greenbuilding at lists.bioenergylists.org>
> *Cc:* Greenbuilding at bioenergylists.org
> *Subject:* Re: [Greenbuilding] Opinions on electric tankless HW heaters?
>
> 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 <613%20756%203884>
>>
>>
>> .............................................................................................................................................
>> 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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