Peak Electric Usage

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I always hear the peak electrical power usage is in the summer in the late  
afternoon.  But looking at my hourly electrical usage over the course of th
e year, it is clear the peak residential usage for anyone with a heat pump  
is in the winter at night.  My peak usage during the summer was less than 4
 kW in any given hour.  My winter peak was more like 12 kW and run like tha
t from 7 PM to 11 AM.  I saw this on six different days this season.  

I realize residential heat pumps aren't the only sink of electrical power,  
but it sure seems like the difference between 4 kW and 12 kW for all those  
heat pumps would make a big dent in the power supply.  Are the other usages
 of electrical power really that shut down on winter nights so that summer  
day usage is dominant?  

Rick C.

Re: Peak Electric Usage
Many heat pump installations include an electric heating element in the air
 box for those days when it is so cold there is just not enough heat out th
ere to pump. If it is turning that element on you are draining about as muc
h as an electric furnace, which is substantial.  

Many people are clueless about this happening if they are on a budget plan  
that averages out the monthly bill over year. It is nice to know what the b
ill will be every month but sometimes you lack information on how much you  
actually use. hey might get a notice of an adjustment saying they will pay  
more in the next year but by then all that money is down the tubes.  

The heat pump is just a compressor which actually cools the outside air. On
e thing that could be wrong is a lack of efficiency causing  it to run almo
st constantly. Another would be some sort of clog in the refrigerant (seale
d system) that would make the motor pull more power. Both are unlikely. If  
you have 240 volts running to the air box inside, more than likely it has a
 heating element in it and that is where the power goes, especially peak po
wer.

Re: Peak Electric Usage
On 2/04/2018 2:23 PM, snipped-for-privacy@gmail.com wrote:
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And of course the old clogged condenser or evaporator

Re: Peak Electric Usage
On Mon, 2 Apr 2018 16:48:39 +0800, Rheilly Phoull

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Or it's running resistive heat.  Mine runs resistive (AUX) if it's
less than about 35-40F outside.

Re: Peak Electric Usage
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In heating mode, because the condenser is inside and gets filtered air the  
more likely clog would be at the evaporator outside. This would not raise t
he operating pressure of the sealed system and therefore would not raise th
e peak load. it can still cost money by the unit having to run the compress
or longer to satisfy the thermostat, but not peak load. However in cooling  
mode it definitely can.  

Another thing that can affect the peak load in the absence of an actual hea
ting coil is a motor run capacitor that is losing capacitance and/or gainin
g ESR. But nothing is like that heating coil, if it is used.

Re: Peak Electric Usage
On Sun, 1 Apr 2018 23:23:37 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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Air-to-air heat pumps are quite usable with outside temperatures
between -10 C and +10 C. Below -10 C the usefulness is questionable
and below -20 C more or less useless (just an expensive electric
heater :-).

That 12 kW sounds a lot if it is the average for several hours and not
from a peak reading meter. That would indicate a very large house or
badly insulated house.

If the outside temperature often drops below -20 C,  I would suggest
installing oil filled electric radiators in those rooms that are
actually used  during winter evenings and nights. The room temperature
can then be set selectively for each room as needed and let the heat
pump maintain say +15 C inside temperature in those rooms that are not
actively used during the night. This reduces the peak demand and also
reduces the heat pump wear.


Re: Peak Electric Usage
On Monday, April 2, 2018 at 6:35:02 AM UTC-4, snipped-for-privacy@downunder.com wrote:
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air box for those days when it is so cold there is just not enough heat out
 there to pump. If it is turning that element on you are draining about as  
much as an electric furnace, which is substantial.  
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That makes no sense.  It is a max of 12 kW during the night when the electr
ic coils run as backup heat.  Whether it was an average or a continuous rea
ding makes little difference.  The electric company gives a total usage in  
graph form either by the month, day or hour of kWHr.  I was looking at hour
ly data where kWHr/Hr is kW.  


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There may be some small benefit to this, but when the rest of the house coo
ls over night and then had to be heated back up the next morning the result
ing savings is much less than you might expect.  The only savings would be  
due to lower heat losses from the lower differential temperatures which at  

emperature precipitously which would put pipes at risk of freezing.  Pipes  
are often in places that are closer to the outside temperature than the roo
m temperature and can freeze if the room temperature drops much below 50  

iginal pipes were run in the outside wall to the kitchen sink.  I had to ri
p up the garage ceiling and move them into the undersink cabinet space so t
his wouldn't repeat.  But even now if the temperature gets much below 50  

 don't want to have to remember to do that *every* night.  

Rick  C.

Re: Peak Electric Usage
On Mon, 2 Apr 2018 05:06:59 -0700 (PDT),
snipped-for-privacy@gmail.com wrote:

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If you only have peak power issues a few days a year, why do you
insist of returning those rooms to "normal" temperatures each morning?


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I have heard of stories of water pipes  _outside_ the building,but
then I thought this must be n urban legend, but then I heard of some
cases in UK, but I would't have expected that such stupidity  is also
possible in the US.

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Re: Peak Electric Usage
On Mon, 02 Apr 2018 16:28:10 +0300, snipped-for-privacy@downunder.com wrote:

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Oh, sure.  Our first house was in a development of raised-ranch (split
foyer), all with[*] oil-fired hydronic heat.  The heat for the upper
floor was run under the floor in the cantilevered area, with no
insulation.  They all froze.

[*] all with avocado refrigerators and harvest gold ovens. Interesting
place

Re: Peak Electric Usage
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It does in some places. In at least one area here if that peak reading goes up the per KWH rate goes up on all usage for that billing cycle.  

Re: Peak Electric Usage
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between -10 C and +10 C."

Yes but with less of an efficiency advantage.  

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I am a big proponent of zone heating, even zone cooling in some cases.  

Granted one might have trouble finding their balls if they go to the bathroom in the middle of the night but if the house is big enough, just how much money is it worth ?  

Re: Peak Electric Usage
On Sun, 1 Apr 2018 23:23:37 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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Resistive heating, of air or water, is crazy inefficient. And
expensive.

--  

John Larkin   Highland Technology, Inc   trk

jlarkin att highlandtechnology dott com
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Re: Peak Electric Usage
On Mon, 02 Apr 2018 14:04:54 -0700, John Larkin

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Come on!  It's 100% efficient!  Can't get better than that.  ;-)

It's not expensive at all.  It's only used when it's too cold for the
heat pump to operate.  Most days it's not cold enough to need the
resistive heat, so it works.  Electricity is pretty cheap, too.  I
think our worst electric bill this Winter was about $250.  Months with
no heat or AC run just under $100.  

Re: Peak Electric Usage
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True, but the major factor is the cost of electricity, not efficiency.

It sounds like you got it good with that cost, here, we don't.

Re: Peak Electric Usage
On Tue, 3 Apr 2018 15:47:59 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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I live in a red state.  The electric rate for those with electric heat
is $.07/kWh, from October to April (or something like that).


Re: Peak Electric Usage
On Monday, April 2, 2018 at 5:05:07 PM UTC-4, John Larkin wrote:
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air box for those days when it is so cold there is just not enough heat out
 there to pump. If it is turning that element on you are draining about as  
much as an electric furnace, which is substantial.  
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Resistive heating is 100% efficient.  It is expensive compared to other met
hods, but it is cheaper than installing other methods.  Since it is only us
ed a relatively small percentage of the time, it is a tradeoff that often f
alls to the side of saving the money on installation.  

What no one seems to grasp is that the peak residential usage is not in the
 summer at all, but in the winter nights.  So if the electrical system as a
 whole has a peak usage on summer days there must be other power usages tha
t are more significant.  

Rick C.

Re: Peak Electric Usage
On Mon, 2 Apr 2018 23:20:36 -0700 (PDT),
snipped-for-privacy@gmail.com wrote:

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Particularly the infrastructure costs.

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That's certainly location dependent.

Re: Peak Electric Usage
On 02/04/2018 22:04, John Larkin wrote:
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Resistive heating of anything is 100% efficient at turning high grade  
electricity into the lowest grade of thermal energy. If you want to warm  
a room up quickly then a fan heater isn't such a bad way to do it.

If you have any alternatives like oil or gas available then they are  
preferable since you get the benefit of all of the heat of combustion  
without turbine and transmission losses along the way.

--  
Regards,
Martin Brown

Re: Peak Electric Usage
On 02/04/2018 07:09, snipped-for-privacy@gmail.com wrote:
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That may be true in lower latitude countries where solar heating is a  
problem but it certainly isn't true in the UK. Consumption here peaks at  
about 6pm in midwinter and is a flat minimum from midnight to 6am.

http://www.gridwatch.templar.co.uk/

Here heating is entirely unnecessary in summer and cooling is only  
needed on a handful of unusually sunny days. You can count on the  
fingers of one had the number of such days per year.

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Why are you aggressively heating the house in the middle of the night?

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Perhaps enough people use oil CH or allow their homes to cool a little  
overnight. It seems overkill to heat a house when everyone is in bed!

--  
Regards,
Martin Brown

Re: Peak Electric Usage
On Monday, April 2, 2018 at 5:25:22 AM UTC-4, Martin Brown wrote:
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Yes, I'm aware of the different heating requirements in Europe.  I had a co
nversation about electricity usage with someone from Germany about this onl
y to realize that they don't heat with electricity at all because their req
uirements make heat pumps entirely impractical.  


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To keep from freezing to death.  As someone else pointed out the most commo
n backup heat for the heat pump is straight resistance heating which has no
 efficiency benefit.  That is why the electric meter spins like a top at ni


ontinue to work well at lower temperatures but maybe I am kidding myself.
  


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 colder should I let it get at night?  

Rick C.  

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