# Average Electricity Usage?

Discussion in 'Home Power and Microgeneration' started by Ted Wood, May 30, 2004.

1. ### John W. HallGuest

I find that strange. The calorific value (which is what most of us are
interested in) of natural gas varies, depending on the source and
perhaps time. Here, they periodically measure the calorific value, and
bill us by the Joule/GigaJoule.
AFAIK, this (by the GigaJoule) applies to residential, commercial and
bulk pipeline rates.

For stripping plants, which remove ethylene etc from the pipeline for
petrochemicals feedstock, I expect other criteria apply.

2. ### danny bursteinGuest

usually not worth swapping.

Let's take a couple of guesses at what you're likely seeing (figuring on a
pretty large and wasteful machine now, and using warm water for the wash,
unheated for the rinses)

a) amount of water saved/load: 20 gallons
(probably half that, but wth...)

b) amount of heated water saved: 5 gallons

c) cost of water [1]: \$0.005 (1/2 cent) per gallon
NYC rate. other urban areas are similar

d) cost of heating water [1] : \$0.01 (1 cent) per gallon

[1] each gallon weighs about 8 pounds,
figure a 50 degree warmup, so that's 2,000 BTUs.

An electrical kw-hr costs (typically, rates
vary a Great Deal) \$0.15 (15 cents) and gives
you 3,500 BTUs. That's \$0.0086 (0.86 cents) for
each gallon... add taxes and summer surcharges.

Ok, so just looking at the various water related costs:

water saved/load: 20 gallons. times 0.5 cents = 10 cents/wash
electrical savings: 5 gallons, times 1 cent/gal = 5 cents/wash

total: 15 cents/wash.

times 5 loads/week = \$0.75 or 75 cents/week.

3. ### danny bursteinGuest

I hate it when my fingers slip... Corrected version below, earlier one
cancelled (but many places will show both. sorry about that.)

4. ### Guest

An assertion demands no more than a counterassertion. To effectively
disagree with basic physics, you need to talk about basic physics...
It isn't enough to wander around the world hurling insults, denying
gravity, and soliciting oral sex from other men

Nick

Tired of Iraq? Do something about it. Learn to halve your energy use
while having fun with math and science.

Join solar guru Steve Baer and PE Drew Gillett and PhD Rich Komp and
me for an all-day workshop on solar house heating and natural cooling
strategies ("HVAC Nonsense") on July 9 in Portland, OR--see page 25 of
http://www.ases.org/conferences/2004_call_for_papers/SOLAR2004_prelim_program.pdf

5. ### Don OceanGuest

Then perhaps you shouldn't do those things.. A hobby mayhaps?

6. ### Pete CGuest

On 31 May 2004 11:33:16 -0400, wrote:

Hi,

Also some houses may allow some humidity to seep in overnight, so the
indoor humidity might be nearly as high as the outdoor humidity by
morning.

cheers,
Pete.

7. ### Bert MenkveldGuest

Hello all,

that the discussion takes place in writing, allowing me time to think things
over before blurting them out in public.

I do not know Nick Pine personally, but I have benefitted from his many
posts in various newsgroups. His attitude may not always be the most
sensitive, but his science generally seems very sound (to my limited
understanding), and his willingness to spend time answering questions is
quite amazing.

If you must compete with Nick, maybe you could try improving on his numbers,
rather than merely criticizing him for using numbers.

Regards,

Bert Menkveld
P.Eng.
bertATgreentronicsDOTcom

[ Stuff snipped that doesn't need to be repeated. ]

8. ### Bert MenkveldGuest

I'm in Elmira, near Waterloo. Are you saying that you don't run your AC in
the summer?
Maybe. In terms of the world at large, it's almost certainly worth doing.
In terms of money, it might be a moot point for the immediate future, but
energy prices are likely to continue rising (I hope).

Our washing machine is on its way out of this world, and I'm looking around
at front loaders. I'd welcome any suggestions for how to assess the likely
reliability of the many new models out there, with very little history
available yet.
It seems natural for people to be set in their ways (I know this from being

Some municipalities apparently ban clothes lines, but allow the smaller
"umbrella" type of outdoor clothes hanging structures.

You could try hanging the clothes to dry indoors for a few weeks and see
what your electrical energy consumption looks like.

9. ### Melodie de l'EpineGuest

I've never done any "scientific" investigation, but I would guess that a
Hills Hoist clothes line ("umbrella") would dry clothes quicker and
reduce wrinkles more than a fence style clothes line (any wind will make
everything turn, which means that even the clothes that didn't catch the
breeze benefit from the breeze... (Am I making sense?)

Not to mention that they can be demountable, foldable etc so that you
can take it out and put it away when you want to use the space for
something else (BBQ, reception, soccer game...)

If you need to dry washing indoors, my own experience has shown that the
best place to put the clothes rack is:
- the room that has a computer on often (extra heat from the computer
helps dry quicker)
- the room that is the "driest" - (works well in my bedroom for really
dry days, slightly humid air is much healthier than dry air)
- the room that has electric heating if you are in a reasonably dry
climate (I don't mean in English climates - helps humidify the air). But
best not to have electric heating at all

Other tips:
-put your drying rack as high up as possible - 1 meter in height can
make a huge difference in time to dry clothes in winter (heat rises)
-best is to have it just below ceiling level
-don't cook sardines or cauliflower when you've got a load of washing
drying. Your clothes will smell (personal experience)
- leave air gapes between the clothes to make sure you get a good air
movement.

About the worst place is in a bathroom that doesn't have a window.

Also, if you hang clothes carefully, you can reduce (or even eliminate)
the need for an iron.

Mel

Bert Menkveld a écrit :

10. ### Fred B. McGalliardGuest

I see Nick's efforts as generally containing some substance and some modest
real experience. A good counter point to my much more theoretical approach.
I second Bert's position.

11. ### Fred B. McGalliardGuest

....
Note to self. Humidity may be regarded in two ways. One is absolute
moisture, the other relative humidity which is a function of the absolute
moisture and the temperature. A shower can put a lot of moisture into a home
in an absolute sense. The heater takes none of this out, even though the
relative humidity can drop like a rock, and your sweating is much more
effective at cooling you off. The air conditioner chills this moisture out
of the air, reducing relative humidity and absolute moisture levels. So when
you open the house at night you can cool it, and raise the relative
humidity, while at the same time removing absolute moisture from the house.

12. ### Guest

There's no change in the absolute humidity above, and no dehum needed
for comfort, but even if so, that's not so bad, if it's only humidity,
vs incoming mist or condensation inside the house. A 2400 ft^2 1-story
house holds 19.2K ft^3 of air that weighs about 1440 pounds. At 75 F
and 50% RH, the humidity ratio w = 0.00942 pounds of water per pound
of dry air, so the air contains about 181 pounds of water vapor. If
and we decided we could live with w = 0.0134:
If we could somehow crank up the RH of the indoor air to 90% at 75 F
overnight, it would contain 325 pounds of water vapor. Removing the extra
325-181 = 144 pounds takes takes 14.4K Btu, which is still a lot less
than the 32.6K Btu in scenario 1.

When is it better to keep the windows closed at night and AC vs vent,
based on humidity gain? It seems better to keep the windows closed if
the temperature of any part of the house is less than the dew point of
the outdoor air, in order to avoid condensation and house heat gain,
but what if the house is warmer than the dew point of the outdoor air?

If the house has volume V and thermal conductance G and continuous heat
gain P (V = 19.2K ft^3 and G = 200 Btu/h-F and P = 2000 Btu/h above), and
we want to maintain indoor temp Ti and humidity ratio wi, and outdoor air
has a 24-hour average temp Ta and wo > wi, and opening windows at night
eliminates the need for AC cooling, we need to dehum 0.075V(wo-wi)1000
Btu/day, but we've saved 24h(P+(Ta-Ti)G) Btu, so opening windows saves
24(P+(Ta-Ti)G)-0.075V(wo-wi)1000 Btu/day, net. Plugging in numbers gives
24(2000+(71.8-75)200)-0.075(19.2K)(wo-0.0134)1000 = 51.9K - 1440Kwo, which
is greater than 0 whenever wo < 0.0360, ie whenever the outdoor air temp
is less than 94 F at night. Looks like opening windows always make sense
in this case, from a humidity point of view.

Nick

Note to self - absolute humidity is not a factor in human
comfort. Cool air with high RH is uncomfortable, and promotes mold
growth. Thus, opening the house during cool damp nights leads to
discomfort and mold growth.

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

14. ### Guest

The ASHRAE 55 comfort zone is defined with absolute humidity limits.

Nick

Bullshit. Utter simplistic complete bullshit.

Are you reading impaired, on top of everything else ?

"This standard specifies the combinations of indoor space environment
and personal factors that will produce thermal environmental
conditions acceptable to 80% or more of the occupants within a space.
The environmental factors addressed are temperature, thermal
radiation, humidity, and air speed; the personal factors are those of
activity and clothing. "

http://www.sfu.ca/FacilitiesManagement/operations/hvac_standards.html

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/

16. ### Guest

And the upper and lower boundaries of the 1981 standard zones are
absolute humidity limits of w = 0.0045 and w = 0.012. RH isn't part
of the comfort zone definition.

Nick

17. ### Fred B. McGalliardGuest

....
I offer this, for fun and profit. Mostly from living in the LA area and up
in Seattle . Except when fiercely cold, we always open the window at night,
and whenever the air is warm enough to let circulation take place without
too much discomfort. Fresh air smells better, and the humidity, usually from
30-70% is much more comfortable than the dead "inside" air. Can't speak to
mold. Not a problem in LA, and in Seattle we keep our house too cold to mold
much. Push the RH up to around 100%, as in serious fog, and it smells damp
and heavy and I expect I would agree. Cool modestly damp nights (as in 70%
RH I think), not so much.

The reason I introduced absolute humidity as an issue is the turning point
of temperature. A standard heating system does not change the absolute
humidity but raises the temperature and thus lowers the RH, partly
contravening the advantage since it causes your sweat to cool you faster.
The inverse of this is a cool night air with a high RH, but less absolute
moisture than the internal house air. If you are concerned with the power it
takes an AC to remove the moisture, you must evaluate temperature and
absolute moisture levels, not just RH. So you could dry the house and cool
it with a colder outside air with a high RH, and your AC would have less
labor, not more. In general, unless you are actually sitting in fog, I go
for the cool night air. I am only vaguely aware of how much this changes
when you are cooking in the steam heat of Ga in summer, but I still usually
go for the fresh air.

18. ### Fred B. McGalliardGuest

....
Shouldn't it be? It is certainly critical to comfort in all the environments
I have experienced?

19. ### Fred B. McGalliardGuest

....
Can't say that I really follow the argument, but the result sounds
consistent with my personal experience.

What he just said is 'open the windows if it's less than 94 F
outside'

Tell me - when it's 90 degrees outside at night, do you open
your windows and find it comfortable to sleep ?

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'

HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/
Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/