Winter heating - energy savings

[Pat-inCO]

I just had a new furnace put in and the guy doing the installation told me
that I should expect a 30% decrease in fuel cost because of the increased
efficiency of the new furnace. I'm happy, but that got me to thinking about
almost thirty years ago when we moved in.

Turns out that I am in a duplex with both sides having the same square
footage and when we moved in, the same furnace, same insulation, etc.
About the middle of the first Winter my step-dad (they lived in the other
half) was complaining about how cold it was when he had to use the little
boys room in the middle of the night. My mother was turning down the
thermostat every night and turning it back up as she got up in the morning.

The energy company was running many advertisements on TV telling
everyone that they would "save energy" and thus money if you turned it
down as you went to bed and back up as you got up. Let me say here that
I was skeptical and was running mine at a constant temperature, for the
comfort.

After one major complaint session by my step-dad I asked my mother if
she still had the last month's heating bill. She did and we compared mine
to hers. A whopping three dollars and some cents difference. I suggested
that she leave it turned up all of the time, to which she said "but we save
money this way!" I said that I would pay the difference in cost if it went up
and she happily decided to try it.

Step-dad was VERY happy with the difference! 8)

Compared heating bills the next month; whopping three dollars and some
cents difference, again. Compared the bills again the next month, same
result. Third month I didn't tell my mother but I turned my thermostat UP
from 68 to 70, and the same three dollars and some cents difference (she
was then running hers at a constant 70 degrees).

My conclusion: This "stuff" that the energy companies are filling our ears
with is pure "stuff", and has no relationship to the truth.

My experiment was under controlled conditions with: the same insulation,
same square footage, same make/model of furnace, same outdoor temp's
(since the two sides are connected), and we had ZERO difference between
changing the temp setting and running constant temp. It also did not make
a difference . . . in cost . . . when I turned mine up by two degrees for
additional comfort.

Each of us must do what we feel best doing, but, IMO, you are fooling
yourself if you think your are saving energy OR cost with running the temp
down at night and back up the next morning. I also found . . no . . difference
in cost with running the indoor temp at 70 vs 68.

Your money and comfort, your decision. 8)

 

[Jimbo357mag]

If you run a scientific study that reduces the set temperature for a set period of time the heating cost will go down a set amount. It has to. It may not be much but as you change the parameters the cost savings will vary also. The speed at which you increase the temperature will have an effect on cost also.

I used to get these questions all the time about heating swimming pools in the winter. Now your talking about some money there.

 

[Pat-inCO]

^^^^

Sigh.

 

[JohnBoy]

Interesting, Pat-inCO - but let us not dismiss the influence of solar gain variability, prevailing winds, potential voids in insulation, utilization of window treatments and variability in traffic in and out of the respective residences. Also, a comparison of specific energy efficiency of each unit. Even the location of the respective thermostats and their relationship with cycling rates needs to be considered. These are the high points - there are additional variables if one wishes to be thorough. (I used to do this sort of analysis for an energy company in a previous life.)

That said, congratulations on your incoming savings with a higher efficiency system! Jon

 

[Pat-inCO]

.... These are the high points - there are additional variables if one wishes to be thorough. (I used to do this sort of analysis for an energy company in a previous life.)

You seem to have missed the word . . . . duplex.

Can you say "cookie cutter" build process?

 

[RugerHound]

What I was told by an HVAC engineer was that turning down the heat at night DOES indeed save "X" amount of energy. Unfortunately heating the area back up to "Y" for the day time consumes most of (or in some cases more) energy as you 'saved'.

If your home is VERY thermally efficient, then you'll realize more savings.
If your home is not quite as thermally efficient, you'll realize less savings.
If your home is full of holes, it ain't gonna make a bit of difference!

 

[Dan in MI]

Pat I'm with John on this. Duplex or not they halves are NOT identical. Do both halves face south? Is the wind hitting both halves equally? Did you and our wife leave for work and then come home at x time, while your in laws were home and going in and out all day? Did they keep the curtains open and you close them? Did they have thin curtains and you had heavy ones? As said, the list goes on and on.


There is a huge number of large differences that were not accounted for in your test.

That said yes, the you will save x% theories are pure estimates based on a very controlled test that gives enough data to make that statement and it not be a lie for legal purposes.

Much like a list I used to see for automotive MPG. There were somewhere near 40 items on this list that each, if fixed on your old car, would save you .5 to 2 MPG. We used to look at an old car and then take the chart and apply what could be fixed on the list. Low and behold we found a bunch of cars that should make gasoline if you completely fixed it!

 

[AJGUNNER]

What about shutting off the hot water heater when you leave for a weekend. I would love to know if the savings from not keeping it hot all weekend, out weights the cost of heating it back up when you get home.

 

[JohnBoy]

.... These are the high points - there are additional variables if one wishes to be thorough. (I used to do this sort of analysis for an energy company in a previous life.)

You seem to have missed the word . . . . duplex.

Can you say "cookie cutter" build process?

No, I did not miss the word 'duplex'. And yes, I can say 'cookie cutter build process'. The variables I referenced do apply to duplex construction. Just as there will be differences in passive gain due to unique usage from various heat-generating appliances and activities, there will be differences in relative heat loss (and gain) in the individual - albeit adjoining - structures.

Again, CONGRATULATIONS on your new investment in energy savings! Jon

 

[Pat-inCO]

What I was told by an HVAC engineer was that turning down the heat at night DOES indeed save "X" amount of energy. Unfortunately heating the area back up to "Y" for the day time consumes most of (or in some cases more) energy as you 'saved'. . . .

BINGO!

We have a winner! 8)

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~


Those of you that want to argue the subtle nuances of test theory,
HAVE AT IT,
in your own thread.

I presented a set of facts, where we changed ONE variable, and observed
the results. Those results were, at first, for three months, BUT held true
for the next FIVE YEARS.

Let me repeat, we varied ONE of the plethora of variables mentioned by
others, and observed the results. Then varied ONE other variable, and
observed the results for years.

You don't believe what I've said? Your problem, not mine. :roll:

Your money and comfort, your decision.

 

[Kevin]

I know after we replaced all the windows and got a new furnace, our heating and cooling are about half of what it was from before. But in Dallas, the summer cooling is more than winter heating. We too however leave the a/c on a constant temperature, the fluctuations back and forth do keep the furnace running as much or more.

 

[Colonialgirl]

Maintaining a constant temperature is more efficient that "yo-yoing" up and down. Keep in mind that is NOT just the air in the rooms that cool down and have to be reheated, BUT also all the furniture, walls, floors and even that ICY COLD toilet bowl.
Think about your auto on a smooth flat level road; Would you "save gas"by slowing down to a set speed and then accelerating back up to a set higher speed? If all my years of driving serve, I THINK NOT; I was always taught (and have observed with speed control) that maintaining a set FIXED SPEED yields the greatest fuel efficiency. SURE kick it out of gear and let the engine idle when coasting down a long hill, but back into gear and your set speed as you reach the bottom. Some of you might even "draft" up close behind a big semi; BUT that's outside the discussion.

 

[Chief 101]

when I left the t-stat alone at 67° instead of the up and down my bill dropped by half, and more.

 

[Jimbo357mag]

What about shutting off the hot water heater when you leave for a weekend. I would love to know if the savings from not keeping it hot all weekend, out weights the cost of heating it back up when you get home.

Yes it will save you some money but not much. Water heaters are pretty well insulated. If you could regulate the heater to slowly heat the water back up you would save even more.

 

[coach]

I just turn down the heat at night a bit just because I find it more comfortable for sleeping. The extra heat as it catches up in the morning feels good after showers and while getting dressed.

 

[blume357]

As has been mentioned there are multiple variables that can apply. Yes, the two duplexes are the closest you can get to exact but as mentioned they won't be perfectly exact.... then again 3-6 dollars a month in most climates during the Winter is not that much of a difference.... could have more to do with how often the outside doors are opened and closed.

As for the on and off... first part of the equation is for how long? Depending on the space there will be a curve that will go from cost more to cost less.

One point that was made... it is not only the air you have to re-heat but also all the mass in the room.

The funny and sad part about all this... the absolute worse way to heat a space... is with heated air.
The less air tight the space the less efficient it is. Also, all this drive to make houses air tight is really going to be bad in the long run... there needs to be a total air transfer every couple of hours in a residence. Long term problem is moisture build up inside the walls....

 

[Big Old Boy]

What Pam said. We went away for three weeks this summer, temp set at 82. When we came home I turned down the temp to 70 and the air ran for 14 hrs to cooll the house.

 

[Jimbo357mag]

Maintaining a constant temperature is more efficient that "yo-yoing" up and down. Keep in mind that is NOT just the air in the rooms that cool down and have to be reheated, BUT also all the furniture, walls, floors and even that ICY COLD toilet bowl.
Think about your auto on a smooth flat level road; Would you "save gas"by slowing down to a set speed and then accelerating back up to a set higher speed? If all my years of driving serve, I THINK NOT; I was always taught (and have observed with speed control) that maintaining a set FIXED SPEED yields the greatest fuel efficiency. SURE kick it out of gear and let the engine idle when coasting down a long hill, but back into gear and your set speed as you reach the bottom. Some of you might even "draft" up close behind a big semi; BUT that's outside the discussion.

Yo-yo-ing is more expensive but if you leave the temp or the speed at a lower setting for a longer period of time it will save you energy/money. ...and again it depends how fast you accelerate back up to normal.

You can also have a good discussion about which is more efficient, a large engine running at half throttle or a smaller engine running at near full throttle.

Another example about heating a pool. If you are only going to use the pool on the weekends at 80* it would be good to hold the temp during the week at a lower but moderate temp of say 74*. But if you are not going to use the pool for a month, go ahead an let it cool to the ambient of 65* and then heat it again.

 

[Cape Cod Terry]

Hi Pat,
I had a new combi boiler/tankless water heater installed last year, the contractor told me to set the thermostat on what I was comfortable and leave it there, I saved well over 30% on my gas bill in the worst winter in history in New England. You can get a 7-day programmable thermostat for $100 or so and install it yourself, you can set it to go lower while you are at work, or at night when your asleep. For more money you can get a Wi-Fi thermostat that will let you monitor and control it from another computer or smart phone, they will also alert you if the heat goes out so you can get it fixed before the pipes freeze. New gas/LP furnaces are in the 95% efficiency range, but that is measured at the furnace. A thirty year old home would likely not have the ductwork leak tested or be insulated to modern R-6 or R-8 standards. If you have air leakage, insuficient duct work insulation, dirty ducts or a bad filter you will never get the results you were promised. Make sure the contractor installed a modern pleated(looks like an accordion) air filter and change it often and get your ductwork cleaned. That will save you more money than fiddling with the thermostat. Check with your contractor or your energy provider to see if you are eligible for a rebate, I got $1500 back on my new boiler. Good Luck,
Cape Cod Terry

 

[Colonialgirl]

Maintaining a constant temperature is more efficient that "yo-yoing" up and down. Keep in mind that is NOT just the air in the rooms that cool down and have to be reheated, BUT also all the furniture, walls, floors and even that ICY COLD toilet bowl.
Think about your auto on a smooth flat level road; Would you "save gas"by slowing down to a set speed and then accelerating back up to a set higher speed? If all my years of driving serve, I THINK NOT; I was always taught (and have observed with speed control) that maintaining a set FIXED SPEED yields the greatest fuel efficiency. SURE kick it out of gear and let the engine idle when coasting down a long hill, but back into gear and your set speed as you reach the bottom. Some of you might even "draft" up close behind a big semi; BUT that's outside the discussion.

Yo-yo-ing is more expensive but if you leave the temp or the speed at a lower setting for a longer period of time it will save you energy/money. ...and again it depends how fast you accelerate back up to normal.

You can also have a good discussion about which is more efficient, a large engine running at half throttle or a smaller engine running at near full throttle.

Another example about heating a pool. If you are only going to use the pool on the weekends at 80* it would be good to hold the temp during the week at a lower but moderate temp of say 74*. But if you are not going to use the pool for a month, go ahead an let it cool to the ambient of 65* and then heat it again.

We aren't talking long periods of time such as several weeks on vacation; In those instances leaving the temp set at the comfortable "COOL" temp during the summer or the comfortable "WARM" setting in winter would asinine. IN both instances the temperature can be reset to maintain a reasonable level, but at the same time conserve Fuel and $$$$$$$$$$$$$$.