I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?

Rick Charnes writes:
I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I think this is a bunch of bunk.

Of course it's a bunch of bunk.

Rick Charnes writes:
I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I'm to believe that you won't save money messing with the thermostat if you
have a heat pump.

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?

Oops. I'm just some guy who posts on usenet g...

-Mike

Rick Charnes wrote in message
...
I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

Turning down the heat saves money for several reasons

a) The temperature difference between the interior and exterior is
smaller. The bigger the difference in temperature the faster heat radiates
to the outside, and the faster cold air convects in through the cracks.

b) Your furnace doesn't actually reach peak efficency until it's been
running for about 10 minutes. By having one big long run in the morning you
run the furnace at it's peak efficency longer. This doesn't apply to
electric heat.

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?

I'm not a heating engineer but this is how it was explained to me.

-- Steve

Rick Charnes wrote:

I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?

It has been figured that you can save roughly 1% of the total
heating bill for *every* degreeF that you turn it down.
Do this GOOGLE:
http://www.google.com/search?hl=en&i...et-back+saving


Jim

Thanks.

My house uses a gas-powered forced hot water heating system. We turn
the heat down to about 60 at night, up to 68 only for about an hour and
a half in the morning, back to 60 when we leave the house for work, then
back up to 68 for the evening.

I think what my friends are saying is that doing this doesn't really
save money because the extra energy involved in the furnace turning
itself up and down a couple of times a day like that balances out the
actual savings on gas.

Is that possible?

In article ,
says...
I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

Turning down the heat saves money for several reasons

a) The temperature difference between the interior and exterior is
smaller. The bigger the difference in temperature the faster heat radiates
to the outside, and the faster cold air convects in through the cracks.

b) Your furnace doesn't actually reach peak efficency until it's been
running for about 10 minutes. By having one big long run in the morning you
run the furnace at it's peak efficency longer. This doesn't apply to
electric heat.

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?

"Speedy Jim" wrote in message ...

It has been figured that you can save roughly 1% of the total
heating bill for *every* degreeF that you turn it down.

I think the real question the OP is asking is not whether you save by
permanently turning the temperature down a few degrees, but if you cycle
between a high and low temperature, i.e. drop from 68 degrees to 60 degrees
overnight for 8 to 10 hours and then restore the 68 degrees for the
remainder of the day.

Besides just the temperature differential of the air between the inside and
outside of the house, doesn't one have to take into account the thermal mass
of everything inside the house. In other words, all your interior walls,
furniture and fixtures will reach the low temperature and how much
additional energy will be needed to restore them to the high temperature.

-al sung
Rapid Realm Technolgy, Inc.
Hopkinton, MA

Rick Charnes writes:
I think what my friends are saying is that doing this doesn't really
save money because the extra energy involved in the furnace turning
itself up and down a couple of times a day like that balances out the
actual savings on gas.

Is that possible?

I suppose it is possible but unlikely. The question is, does the
furnace spend less time turned on while heating the house up in the
morning than it would spend turned on overnight to keep the house at
the daytime temperature? The answer is almost certainly yes, in which
case you're saving money by turning the heat down overnight.

You can confirm this by measuring (a) how much time your furnace spends
turned on in an hour during a cold day/night while trying to keep the
house at your daytime tempature and (b) how much time your furnace
spends turned on in the morning heating the house up from its nighttime
temperature to its daytime temperature. Multiply the time you measured
in (a) by however many hours you typically turn the heat down for at
night, and I believe you will find that the resulting time is
significantly longer than what you measured in (b).

As other people have pointed out, your furnace is more efficient when
it runs for a while, so that's another reason why it's cheaper to heat
the house up all at once in the morning rather than doing it all night.

Also, since the temperature drops markedly during the night, the
difference between the inside and outside temperatures is higher at
night, which means its more expensive to heat the house then.

Basically, there's no factual basis for what your friends are telling
you.

Some references to tell your friends to read if they persist in their
incorrect assertion:

http://www.alliantenergy.com/stellen..._ns_index.hcsp
http://www.ornl.gov/sci/roofs+walls/...l/results.html
http://www.hud.gov/offices/pih/progr...c/strat_H5.cfm
http://www.dep.state.pa.us/dep/deput...HRM_100396.htm

Here's a reference to a page which explains the claim someone else made
here that heat-pump systems may save less when set back at night:

http://oee.nrcan.gc.ca/publications/...p_Section7.cfm

You can find lots more about this if you Google for "setback savings."

Rick Charnes wrote in
:
I think what my friends are saying is that doing this doesn't really
save money because the extra energy involved in the furnace turning
itself up and down a couple of times a day like that balances out the
actual savings on gas.

That's really foolish.

Think of a full drum of water with a small leak in it. The higher the
drum is filled with water, the higher the pressure and so the faster the
leak.

Of the following, which takes more water?

(a) keep the drum constantly filled, working against the spurting leak

(b) let the drum run down some, so the leak is slower, then fill it up
later when needed.

Of course, the answer is (b). In the case of the house, the "pressure"
driving the leak is the temperature difference between the inside and
outside.

To translate your friends' point to the water drum, they are saying that
in (b), it takes a lot of water to fill it back up, so it it better to
keep it filled because you don't need to put in a lot of water at any
given time. But in both cases the drum is full at the start and at the
end; all you are doing is replacing the stuff that leaks out. More leaks
out in (a) than in (b), so you pay less in (b).

In the case of the house, the end point in both cases is a warm house.
The only question is how much energy will leak out.

By the way it is not true that a 1 degree setback saves 5%. This can't
possibly be true, since it depends on the size of the gas bill. In a
cold climate, it saves much less than 5% (but it still saves a lot since
it is a % of a large bill). In a warm climate it can save more than 5%,
but that's a % of a much smaller bill.

As other people have pointed out, your furnace is more efficient when
it runs for a while,

It's clear to me now that savings accrue from turning it down to 60 at
night. But I would imagine that turning it up to 68 in the morning at 7
am then back to 60 only an hour and a half later when we leave for work
might not be the pinnacle of efficient use of the furnace. But I think
doing so is still a lot more energy-saving than leaving it on at 68 all
day when we're not at home, yes?

You guys are great -- I really appreciate this help.

Rick Charnes wrote:
As other people have pointed out, your furnace is more efficient when
it runs for a while,

It's clear to me now that savings accrue from turning it down to 60 at
night. But I would imagine that turning it up to 68 in the morning at 7
am then back to 60 only an hour and a half later when we leave for work
might not be the pinnacle of efficient use of the furnace. But I think
doing so is still a lot more energy-saving than leaving it on at 68 all
day when we're not at home, yes?

Sure, it's not as efficient as just leaving the 'stat at 60 all morning, but
comfort does mean something (after all, for max efficiency, just turn the
furnace off...not real comfortable, 'tho).

Alan Sung wrote:

"Speedy Jim" wrote in message ...

It has been figured that you can save roughly 1% of the total
heating bill for *every* degreeF that you turn it down.


I think the real question the OP is asking is not whether you save by
permanently turning the temperature down a few degrees, but if you cycle
between a high and low temperature, i.e. drop from 68 degrees to 60 degrees
overnight for 8 to 10 hours and then restore the 68 degrees for the
remainder of the day.

Besides just the temperature differential of the air between the inside and
outside of the house, doesn't one have to take into account the thermal mass
of everything inside the house. In other words, all your interior walls,
furniture and fixtures will reach the low temperature and how much
additional energy will be needed to restore them to the high temperature.

You still save money. And you don't understand what thermal mass is.

On Tue, 9 Dec 2003 15:18:13 -0500, Rick Charnes wrote:

I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?


Let me answer your question in a different way which is non technical.
I think unless you've been too busy over the years to listen / read
about related topics I'd say the following answer will suffice. If a
majority of people say it will save money but a minority say it won't
save money, who would you believe. I think this question has been
around long enough to get a fair distribution of yes / no answers. If
this doesn't answer your question, go to several heating suppliers in
your area and ask them what they think.

"Bill Seurer" wrote in message
...
Alan Sung wrote:

"Speedy Jim" wrote in message
...

It has been figured that you can save roughly 1% of the total
heating bill for *every* degreeF that you turn it down.

,,,.

Besides just the temperature differential of the air between the inside
and
outside of the house, doesn't one have to take into account the thermal
mass
of everything inside the house. In other words, all your interior walls,
furniture and fixtures will reach the low temperature and how much
additional energy will be needed to restore them to the high
temperature.

You still save money. And you don't understand what thermal mass is.

The statement was made to add an element to the discussion. I did not make
any claims as to any knowledge of thermal mass and I certainly don't have
any expertise in that area. I just think that there is more to this than the
"water in the barrel" examples.

-al sung

On Thu, 11 Dec 2003 07:42:24 -0600, frankg wrote:

On Tue, 9 Dec 2003 15:18:13 -0500, Rick Charnes wrote:

I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?


Let me answer your question in a different way which is non technical.
I think unless you've been too busy over the years to listen / read
about related topics I'd say the following answer will suffice. If a
majority of people say it will save money but a minority say it won't
save money, who would you believe. I think this question has been
around long enough to get a fair distribution of yes / no answers. If
this doesn't answer your question, go to several heating suppliers in
your area and ask them what they think.


As a follow up to answer the question in a technical way, I think the
answer depends on the efficiency of your heater vs. the efficiency of
your home. But I believe my earlier post is still correct regarding
asking heating suppliers in YOUR area. They probably are more
educated on the local construction and heating needs for most homes
there. If you need a more technical answer, consult a HVAC engineer.

frankg writes:
As a follow up to answer the question in a technical way, I think the
answer depends on the efficiency of your heater vs. the efficiency of
your home.

No, it really doesn't. Regardless of how efficient the heater
and the building are, turning down the thermostat will always
save money; the only thing affected by the efficiency is *how
much* money will be saved.

"Alan Sung" wrote in message
news:7%GBb.500455$Fm2.479732@attbi_s04...
"Speedy Jim" wrote in message
...

It has been figured that you can save roughly 1% of the total
heating bill for *every* degreeF that you turn it down.

I think the real question the OP is asking is not whether you save by
permanently turning the temperature down a few degrees, but if you cycle
between a high and low temperature, i.e. drop from 68 degrees to 60
degrees
overnight for 8 to 10 hours and then restore the 68 degrees for the
remainder of the day.

Besides just the temperature differential of the air between the inside
and
outside of the house, doesn't one have to take into account the thermal
mass
of everything inside the house. In other words, all your interior walls,
furniture and fixtures will reach the low temperature and how much
additional energy will be needed to restore them to the high temperature.

The thermal mass will also work in reverse. It will slow down the cooling to
the lower temperature, such that in the end it cancels out.

"Alan Sung" wrote in
news:WD_Bb.500928$HS4.3868356@attbi_s01:

You still save money. And you don't understand what thermal mass is.

The statement was made to add an element to the discussion. I did not
make any claims as to any knowledge of thermal mass and I certainly
don't have any expertise in that area. I just think that there is more
to this than the "water in the barrel" examples.

It does not add any element to the discussion, since you don't understand
what thermal mass is. What you "just think" is not important.

frankg wrote in
:


Let me answer your question in a different way which is non technical.
I think unless you've been too busy over the years to listen / read
about related topics I'd say the following answer will suffice. If a
majority of people say it will save money but a minority say it won't
save money, who would you believe. I think this question has been
around long enough to get a fair distribution of yes / no answers. If
this doesn't answer your question, go to several heating suppliers in
your area and ask them what they think.

Ah, it's like Family Feud: "survey says". It's not a matter of logic or
experimentally verifiable fact, it's just majority opinion.

Chuckles writes:
What you "just think" is not important.

Al - I enjoyed your contribution to the thread and ignored
Chuckles'. You decide...

-Mike

Interesting debate I seem to have started. Out of curiosity, I sent the
question in an email to KeySpan Energy, my local heating gas supplier
here in Boston. They're hardly a neutral observer, but I wanted to see
what they would say. I noticed that they have an online document "20
Ways to Use Energy Smarter" in which one of the items says:

17. Install a clock thermostat, and set it to automatically drop to a
lower temperature at night.

So to confirm, I wrote:

"I use gas-powered forced hot water heating in my house. We turn the
heat down to about 60 at night, up to 68 in the morning, back to 60 when
we leave the house for work, then back to 68 for the evening. Some
friends have suggested, though, that doing this doesn't really save
money, because the extra energy involved in the furnace turning itself
up and down a couple of times a day balances out the actual savings on
gas. Can KeySpan help clarify?"

Their reply:
"We recommend leaving the thermostat at one setting at all times.
It's more efficient that way rather than turning the thermostat
down to 60' and the back up to 68'. Thermostat settings should
not vary more than 3'."

Hmmmmmmmm....

Rick Charnes wrote in message . ..
I have a couple of friends who insist that "they've heard" that turning
the heat down in your house for the night really doesn't save money,
allegedly because "it takes a lot of energy to be turning the furnace up
and down like that."

I think this is a bunch of bunk. Can any heating engineers give us the
definitive word on this?

Standard "I'm-not-a-heating-engineer-but" disclaimer...

We use a programmable thermostat, and it has saved us a LOT. Best $85
we ever spent. We used to turn the heat up and down manually in our
old place, which was a pain, and either expensive or chilly if you
forgot to change the thermostat. We keep our current house at about 17
degrees Celcius (sorry, don't know the Farenheit conversion) while
we're there and awake, and the thermostat automatically turns it down
to 12 when we leave for work and when we're sleeping. This has saved
us at least $20-$30 per month on our bill, plus a lot of aggravation
in not having to think about the system.

It probably helps that our house is quite heat efficient - 1 level
plus basement, large south windows, high R-value attic insulation -
and that we tend to add clothes instead of turning up the heat if
we're cold.

And now a slight thread hijack and appeal for frugal opinions...

We're on what's called an "equal payment plan" with our natural gas
bill. We pay a set amount each month regardless of actual energy
consumption, and the company reconciles the account at the end of each
year and you either get a credit or an extra bill for the amount
that's over or under. Generally this means that we have 1-3 months
with a $0 gas bill, as we're quite frugal with our heat.

In our last house this made sense, as it was an old place with single
pane windows and a nightmare to heat $$-wise. No equal payment would
have meant that we were paying at least $230 per month in winter. In
our new place, however, we're currently running a $250 surplus on our
bill, paying $95 per month, and the surplus keeps going up (plus there
is a gas rate cut coming in January). We turn the heat right off from
about May to early October, and only have the gas stove and hot water
heater going during that time, which means that in summer we're paying
way more than we need to.

Should I try going off the equal payment plan and paying the "real"
monthly cost? Or am I better off with the known quantity? FWIW I am
mildly annoyed by the idea that I'm floating the gas co. a free loan,
but don't want to get suddenly hit with a huge bill next month (even
though I don't think that will happen). I'm planning to call the gas
co. and get the actual cost of energy for the last 2-3 months...if
it's below $95 I may bail off the equal pmt plan.

Thanks for your opinions!

- ScorpioChick

Rick Charnes writes:
"We recommend leaving the thermostat at one setting at all times.
It's more efficient that way rather than turning the thermostat
down to 60' and the back up to 68'. Thermostat settings should
not vary more than 3'."

I suggest you send them some of the URLs I posted yesterday,
as well as the excerpt from their own Web site recommending
the installation of a clock thermostat and a lower night
temperature, and ask them how their answer to you can be
reconciled with all of that contradictory information.

On Thu, 11 Dec 2003 14:05:13 +0000 (UTC), (Jonathan Kamens) wrote:

frankg writes:
As a follow up to answer the question in a technical way, I think the
answer depends on the efficiency of your heater vs. the efficiency of
your home.

No, it really doesn't. Regardless of how efficient the heater
and the building are, turning down the thermostat will always
save money; the only thing affected by the efficiency is *how
much* money will be saved.

Obviously you don't sound too technical so I won't bother to explain.

Bill 2 wrote:
The thermal mass will also work in reverse. It will slow down the cooling to
the lower temperature, such that in the end it cancels out.

Thermal Mass works to your advantage when the outside temperature
fluctuates above and below the inside temp. Then the thermal mass of
the house works to reduce the need for both (either) heating and A/C.

If someone says a certain style of house is good in winter because it
has a lot of thermal mass they don't know what they are talking about.

"Scorpio Chick" wrote in message

We're on what's called an "equal payment plan" with our natural
gas
bill. We pay a set amount each month regardless of actual
energy
consumption,....
.. we're currently running a $250 surplus on our
bill, paying $95 per month, and the surplus keeps going up

Should I try going off the equal payment plan and paying the
"real"
monthly cost? Or am I better off with the known quantity? FWIW
I am
mildly annoyed by the idea that I'm floating the gas co. a free
loan,
but don't want to get suddenly hit with a huge bill next month
(even
though I don't think that will happen). I'm planning to call
the gas
co. and get the actual cost of energy for the last 2-3
months...if
it's below $95 I may bail off the equal pmt plan.

You could call the gas company and ask them to adjust the amount
they bill to match reality. They are currently just making free
use of your money.

Bob

Bob wrote:
"Scorpio Chick" wrote in message

We're on what's called an "equal payment plan" with our natural gas
bill. We pay a set amount each month regardless of actual energy
consumption,....
.. we're currently running a $250 surplus on our
bill, paying $95 per month, and the surplus keeps going up

Should I try going off the equal payment plan and paying the "real"
monthly cost? Or am I better off with the known quantity? FWIW

I am mildly annoyed by the idea that I'm floating the gas co. a free
loan, but don't want to get suddenly hit with a huge bill next month
(even though I don't think that will happen). I'm planning to call
the gas co. and get the actual cost of energy for the last 2-3
months...if it's below $95 I may bail off the equal pmt plan.

You could call the gas company and ask them to adjust the amount
they bill to match reality. They are currently just making free
use of your money.

Bob

It sounds like you are in the norther hemisphere. Jan and Feb are
coming, and it is normal to have a "surplus" on your bill at this
time of the heating season. That is the way they do the budget billing.
--Phil
--
Phil Munro Dept of Electrical & Computer Engin
Youngstown State University
Youngstown, Ohio 44555

frankg wrote in
:

On Thu, 11 Dec 2003 14:05:13 +0000 (UTC),
(Jonathan Kamens) wrote:

frankg writes:
As a follow up to answer the question in a technical way, I think the
answer depends on the efficiency of your heater vs. the efficiency of
your home.

No, it really doesn't. Regardless of how efficient the heater
and the building are, turning down the thermostat will always
save money; the only thing affected by the efficiency is *how
much* money will be saved.

Obviously you don't sound too technical so I won't bother to explain.

But he's right. It is independent of the efficiency of the heater and the
efficiency of the home. There are higher-order corrections if the
efficiency of the heater is variable, but the efficiency of the home never
enters into it. Is that technical enough?

In article ,
says...
Rick Charnes writes:
"We recommend leaving the thermostat at one setting at all times.
It's more efficient that way rather than turning the thermostat
down to 60' and the back up to 68'. Thermostat settings should
not vary more than 3'."

I suggest you send them some of the URLs I posted yesterday,
as well as the excerpt from their own Web site recommending
the installation of a clock thermostat and a lower night
temperature, and ask them how their answer to you can be
reconciled with all of that contradictory information.

Right -- I did reply, and sent them the excerpt from their Web site.
Here's their reply to my reply:

"I'm familiar with our website and conservation programs, however,
you can lower the thermostat at night but we still recommend
not more than 3 degrees. It takes more energy to bring the heat
back up to the morning setting."

So I guess we're back to my original question. But it just doesn't make
sense. What is this "bringing the heat back up takes more energy"
concept, anyway? Say from midnight to 5 am I'm at 60 degrees,
definitely saving money over 68. Now the thermostat kicks in at 5:30
and starts its climb back to 68 which it'll hit at 7:00 am. For this
hour and a half it's certainly using more gas than it was at 60, but I
have to imagine less than it would at 68.

Is he suggesting that the climb up from 60 to 68 uses more gas than
hovering at 68 does? I can't imagine why that would be.

Rick Charnes writes:
"I'm familiar with our website and conservation programs, however,
you can lower the thermostat at night but we still recommend
not more than 3 degrees. It takes more energy to bring the heat
back up to the morning setting."

I have no idea why Keyspan is telling you this. It contradicts every
other source of information about this I've ever seen or heard. And I
can't imagine what the scientific basis for their assertion might be.

On Fri, 12 Dec 2003 17:26:29 GMT, Chuckles wrote:

frankg wrote in
:

On Thu, 11 Dec 2003 14:05:13 +0000 (UTC),
(Jonathan Kamens) wrote:

frankg writes:
As a follow up to answer the question in a technical way, I think the
answer depends on the efficiency of your heater vs. the efficiency of
your home.

No, it really doesn't. Regardless of how efficient the heater
and the building are, turning down the thermostat will always
save money; the only thing affected by the efficiency is *how
much* money will be saved.

Obviously you don't sound too technical so I won't bother to explain.

But he's right. It is independent of the efficiency of the heater and the
efficiency of the home. There are higher-order corrections if the
efficiency of the heater is variable, but the efficiency of the home never
enters into it. Is that technical enough?

Actually I'm right.

"Jonathan Kamens" wrote in message
...
Rick Charnes writes:
"I'm familiar with our website and conservation programs, however,
you can lower the thermostat at night but we still recommend
not more than 3 degrees. It takes more energy to bring the heat
back up to the morning setting."

I have no idea why Keyspan is telling you this. It contradicts every
other source of information about this I've ever seen or heard. And I
can't imagine what the scientific basis for their assertion might be.

They are probably telling you this so you burn more gas and they make more
money.

Has anyone actually tried measuring it? My thermostat will keep track of the
total time the furnace was on: today, yesterday, and total. Assuming
exterior weather conditions are similar, you can run it a couple days
without turning down the temperature, and a couple days with the temperature
turned down at night and during the day and look at the results.

In article ,
says...

"Jonathan Kamens" wrote in message
...
Rick Charnes writes:
"I'm familiar with our website and conservation programs, however,
you can lower the thermostat at night but we still recommend
not more than 3 degrees. It takes more energy to bring the heat
back up to the morning setting."

I have no idea why Keyspan is telling you this. It contradicts every
other source of information about this I've ever seen or heard. And I
can't imagine what the scientific basis for their assertion might be.

They are probably telling you this so you burn more gas and they make more
money.

....or perhaps they're short on supply at 6:00AM, when everyone's
thermostat kicks in.

Has anyone actually tried measuring it? My thermostat will keep track of the
total time the furnace was on: today, yesterday, and total. Assuming
exterior weather conditions are similar, you can run it a couple days
without turning down the temperature, and a couple days with the temperature
turned down at night and during the day and look at the results.

The variation from day to day will swamp your measurement.
Simple physics tells us it's true though. The heat loss is
proportional to the difference in temperature. The numbers
advertised here are 3% per degree*day. I find that somewhat high
given the number of heating-degree-days, but it's not that bad.

--
Keith