I normally keep my house around 68* F during the day when someone is at
the house. If we are not at the house, or are sleeping, I have the
thermostat set to drop down to 58*. Does anyone know if there is a
recommended drop amount, to get the most efficiency for your fuel?
Also, is there a more efficient temp to run at during the day?

Kind of how 55mph is most efficient at using gas?

(I know results will vary based on insulation, etc)

"Matt" wrote in message
...
I normally keep my house around 68* F during the day when someone is at
the house. If we are not at the house, or are sleeping, I have the
thermostat set to drop down to 58*. Does anyone know if there is a
recommended drop amount, to get the most efficiency for your fuel?
Also, is there a more efficient temp to run at during the day?

There are a lot of variables that will affect the answer to your question.
The outside temperature, your house's insulation quality, at what
temperature you're comfortable, whether you are using gas, electricity, wood
or ???

No single pat answer. However, if dropping the temperature at one time of
the day results in a need for an extended FULL BURN to get the temperature
up to where you need it when you get home, you are probably not getting an
advantage by dropping the temperature, and my actually be less efficient.

68 degrees around the clock.

Gorky wrote:
"Matt" wrote in message
...
I normally keep my house around 68* F during the day when someone
is at the house. If we are not at the house, or are sleeping, I
have the thermostat set to drop down to 58*. Does anyone know if
there is a recommended drop amount, to get the most efficiency for
your fuel? Also, is there a more efficient temp to run at during
the day?

There are a lot of variables that will affect the answer to your
question. The outside temperature, your house's insulation quality,
at what temperature you're comfortable, whether you are using gas,
electricity, wood or ???

No single pat answer. However, if dropping the temperature at one
time of the day results in a need for an extended FULL BURN to get
the temperature up to where you need it when you get home, you are
probably not getting an advantage by dropping the temperature, and my
actually be less efficient.

Sorry, not true.

http://www.eere.energy.gov/consumerinfo/pdfs/thermo.pdf

A common misconception associated with
thermostats is that a furnace works harder
than normal to warm the space back to a
comfortable temperature after the thermostat
has been set back, resulting in little or
no savings. This misconception has been
dispelled by years of research and numerous
studies. The fuel required to reheat a
building to a comfortable temperature is
roughly equal to the fuel saved as the
building drops to the lower temperature.
You save fuel between the time that the
temperature stabilizes at the lower level
and the next time heat is needed. So, the
longer your house remains at the lower
temperature, the more energy you save.

Matt wrote in
:

I normally keep my house around 68* F during the day when someone is
at the house. If we are not at the house, or are sleeping, I have
the thermostat set to drop down to 58*. Does anyone know if there
is a recommended drop amount, to get the most efficiency for your
fuel?

A general answer is "the lower the better".

Also, is there a more efficient temp to run at during the day?

Kind of how 55mph is most efficient at using gas?

(I know results will vary based on insulation, etc)

The period of setback is just as important as the temperature setting.
The longer that you can leave the thermostat set to a lower
temperature, the better the efficiency gain.

If you adjust the temperature to a lower level, there will be a time
period when the temperature is dropping to the new setting. Over this
time period, you are not gaining any efficiency, since that lost heat
must be replaced as soon as you turn the thermostat back to the higher
setting. However, once the temperature has stabilized at the lower
value, then the lower heat loss through your insulation is pure
efficiency gain.

An almost perfect analogy for this is to think of your house as a bucket
of water with a small hole in the bottom, and your furnace is the water
tap working to keep it filled up to a certain level. The hole in the
bucket is a good analog for the heat loss through your insulation. A
smaller hole equals better insulation. The distance from the water
surface to the hole equals the temperature differential between inside
and outside temperatures -- higher level differences will result in
higher water flow through the hole (just like higher temperature
differentials result in higher heat flow through the insulation).

When you turn down the tap volume, the water will take some time to
stabilize at a lower level. Once stabilized, the new lower tap volume
can be maintained indefinitely. When you want to go back to the higher
level, you must add enough water to bring the level back up to the
original, and then you can set the tap volume to the original setting.

In article ,
says...

A common misconception associated with
thermostats is that a furnace works harder
than normal to warm the space back to a
comfortable temperature after the thermostat
has been set back, resulting in little or
no savings.

One case where this concern can be quite valid is heat pumps with
electric resistance backup heating.

When it's time to warm the house back up, the heat pump is too slow by
itself so the system turns on electric heaters to speed up the heating,
so suddenly you've gone from an extremely efficient heating method to one
of the most expensive.

--
is Joshua Putnam
http://www.phred.org/~josh/
Braze your own bicycle frames. See
http://www.phred.org/~josh/build/build.html

Joshua Putnam wrote:
In article ,
says...

A common misconception associated with
thermostats is that a furnace works harder
than normal to warm the space back to a
comfortable temperature after the thermostat
has been set back, resulting in little or
no savings.

One case where this concern can be quite valid is heat pumps with
electric resistance backup heating.

When it's time to warm the house back up, the heat pump is too slow by
itself so the system turns on electric heaters to speed up the
heating, so suddenly you've gone from an extremely efficient heating
method to one of the most expensive.

True. OTOH if it were my system I'd install a heat-strip lockout so that
the strips wouldn't come on as long as the outdoor temperature was high
enough for proper HP operation. Also, many 'adaptive learning' thermostats
will figure out when they need to turn on the (slower) HP in order to get
the temperature restored at the programmed time.

I've wondered this....

I've heard the argument that dropping 5 or 10 degrees at night/day when
you aren't there saves energy.. but I've also heard that keeping things
up to temp saves energy cause once you are up.. you are up.. and just
have to keep things there and there is no 'refractory period' where
things have to heat up and start holding warmth again (ie not feel cold
to touch)

wrote:
68 degrees around the clock.

True. OTOH if it were my system I'd install a heat-strip lockout so that
the strips wouldn't come on as long as the outdoor temperature was high
enough for proper HP operation. Also, many 'adaptive learning' thermostats
will figure out when they need to turn on the (slower) HP in order to get
the temperature restored at the programmed time.



While I don't have a heatpump (I have oil heat).. I do have an adapter
thermostat and it's very nice... if you tell it to be at 68 or 69 at
8:00am, it will be there at 8:00am.... it says RECOV on the console when
it's recovering to the pre-programmed temp.

On Thu, 16 Dec 2004 14:28:02 -0500, someone wrote:


Kind of how 55mph is most efficient at using gas?

A gross misunderstanding. 55 is not the "most efficient" in any
general sense, its a compromise between the desire to get someplace
quickly and the desire to have better fuel economy.

Things like airplanes that need to go forward to stay aloft, DO have a
specific speed for least fuel consumption. And since most cars have
discrete gears rather than continuously variable transmissions, below
some ridiculous point the car would probably run"inefficiently".

But in general slower burns less fuel, and if you didn't go at all,
then that burns the least. And you house is pretty much the same way.
The lower the temp the less fuel used. And if you didn't heat it at
all, that's the least used.

My first engineering job was running heat loss calcs, in the days
before computers were in common use. The first parameter is "delta
T", the difference between desired inside and the ambient outside
temps. The lower the delta T the less btus used, in general its as
simple as that.

Sorry, it is a judgment call, there is no one temp that you can smugly
say "this is the BEST temperature, I found out on the internet".


Reply to NG only - this e.mail address goes to a kill file.

Matt wrote:

I normally keep my house around 68* F during the day when someone is at
the house. If we are not at the house, or are sleeping, I have the
thermostat set to drop down to 58*. Does anyone know if there is a
recommended drop amount, to get the most efficiency for your fuel?
Also, is there a more efficient temp to run at during the day?

Kind of how 55mph is most efficient at using gas?

(I know results will vary based on insulation, etc)


We quite trying to make sense of thermostat settings years ago. Last one
awake in hour house gets the temp. they want"-)