[Greenbuilding] cost to run appliance--math help

Benjamin Pratt benjamin.g.pratt at gmail.com
Mon Nov 21 07:38:37 PST 2011

My house came with a small "Instant hot water dispenser" to keep 1/2
gallon of water at 190 degrees f. I've had it unplugged since day one
because i thought it was wasteful expensive to run. My wife wants to
use it this winter and asked me how much it would cost us. Good
question. Can anyone give me an estimate on how much it costs to
run--versus a kettle or a microwave? The math is difficult for me, and
i have no idea how often it would run. I suppose i could put it on a
timer to turn it off at night...

It is 115v 6.5A 750w, and has 1/2" or so expanded foam insulation but
not complete on all sides.
Our energy cost is about $0.09 kWh


On Sun, Nov 20, 2011 at 1:01 PM, Gordon Howell -- Howell-Mayhew
Engineering <ghowell at hme.ca> wrote:
> Hello Gennaro:
> I can appreciate your comments about the green building list being about
> green building.  My read of it was that Nick was responding to the incorrect
> use of "kilowatts" to refer to energy -- and I agree with Nick and the
> strength of his comments re the misuse of kilowatts.  I am on a similar rant
> against this misuse -- even with electric utilities and electricity
> regulators (imagine!).
> Frank Tettemer should have said "kilowatt-hours".  I am amazed at how many
> people mix up the terms "kilowatts" (of power) and "kilowatt-hours" (of
> energy) ... we don't mix up "kilometres per hour" (of speed) and
> "kilometres" (of distance) (or "miles per hour" and "miles") so why do we
> mix up energy and power?  ("power" is not electricity in the slightest...
> electricity is electric charges)
> Power (watts, W), speed (kilometres per hour, km/h), electric current
> (amperes, A) and frequency (hertz, Hz) are respectively merely rates of
> change in energy (joules, J), distance (kilometres, km), electric charge
> (coloumbs, C) and states (cycles of anything), but people seem to be
> commoditising power as if it is something that is bought and sold.  This is
> getting a lot of people really confused, unfortunately, when it is instead a
> very simple concept.
> The only reason why there is any issue with this is because the Sumerians
> developed the sexagecimal system over 4000 years ago
> <http://en.wikipedia.org/wiki/Sexagesimal> that gave us 60 minutes per
> hour... (thanks guys)
> I welcome anyones comments.
> +Gordon Howell, P.Eng.
> Edmonton
>> Date: Fri, 18 Nov 2011 17:57:24 -0500
>> From: Gennaro Brooks-Church - Eco Brooklyn <info at ecobrooklyn.com>
>> To: Green Building <greenbuilding at lists.bioenergylists.org>
>> Subject: Re: [Greenbuilding] Fwd: energy savings myths
>> This list is about green building. not just energy. learn the distinction.
>> its about time you did.
>> Gennaro Brooks-Church
>> 347-244-3016
>> On Nov 18, 2011 5:43 PM, "nick pine" <nick at early.com> wrote:
>> > Gennaro Brooks-Church - Eco Brooklyn <info at ecobrooklyn.com> wrote:
>> >
>> >  After building a Passive House in NY I learned it only needed
>> > insulation
>> >> to code - R18. What made it or broke it was how well the 6mil plastic
>> >> air
>> >> barrier was sealed. Just a one inch hole in the plastic rendered the
>> >> house
>> >> unable to heat with the tiny mini-splits. Seal the hole and you can
>> >> heat
>> >> the house with a hair drier.
>> >
>> > Absolute bull****! Hogwash! Rubbish! Nitwit! Try using actual numbers!
>> >
>> > Frank Tettemer <frank at livingsol.com> wrote:
>> >
>> > Even having been experimenting and physically working on these questions
>> > for over fourty years, it has taken most of a generation of time to cut
>> > our household's daily energy consumption to two armloads of firewood,
>> > about a dollar's worth of propane, and two to four kilowatts of
>> > electricity per day.
>> >
>> > More absolute bull****... Kilowatts are power, not energy. This list is
>> > about energy. Learn the difference between power and energy!
>> >
>> > Nick
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b e n j a m i n p r a t t

professor art+design
the university of wisconsin stout

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