So am I REALLY saving gas turning down the thermostat???

[mattl]

I've had a cold for about a week now and feeling a bit brain dead, so I thought I'd toss this out for group discussion.  Not sure if my logic is faulty or not...

During the day when I'm around I keep the heat at 65. At night I had set it to turn down to 60, then 55 and now 50.  I like it cool when I sleep and 50 does not bother me.  I have the thermostat programmed to boost the heat to 62 at 8 AM and it drops to 50 at 9 PM.  I've not noticed the burners kicking in during the night, the accumulated heat just slowly drops down.  It's a CAC unit so the fan is circulating air at all times.

The last few weeks the temp has been in the low to mid teens at night and I notice the furnace kicking into high, it's a dual burner, for about an hour in the morning.  It's a 75,000 BTU unit and on low, which it uses 90% of the time I think it's 30,000 BTUs.  So at the moment it's burning a lot of gas for an hour or an hour 15.

My question is as I really saving that much gas by doing this?  If it modulated on at night for 5 or 10 minutes once or twice an hour at 30,000 BTUs would it not use about the same amount of gas as not running and then basting for 60-75 minutes?  It's hard to do a strict comparison due to temp fluctuations, but logic seems to tell me I'm not that much ahead.
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Ok, did a bit of scratch pad calculating.  Just using easy to compute numbers lets say :

75,000 BTU/hr cost $10
then ---> 30,000 BTU/hr costs $4.

So, the burner could run for 150 minutes at the same gas usage at the lower setting.  If the heat is basically off for 10 hours the burner could run 15 minutes an hour and cost the same, correct?  Am I missing something?

 

[3beltwesty]

Here at my plant in the deep south it has a two stage gas heater from circa 1985.

The thermostat's set point versus room air temp difference determines whether one or both burners kick in.

Thus when I left the heater off a weekend ago it was 50F inside at 7:30am on a Monday, and 24F outside.

Turning the thermostat to 70 kicks in both 125,000 BTUH burners then the extra one turns off when the air approaches 70F. Then during the day the single burner turns on and off and on, keeping the 70F air temp.

Turning the thermostat lower uses less gas. The odd thing is that even when the air temp is raised in the Morning; all that stuff/crap is still cold. The air only is about 1/2 or less of the thermal mass. Thus one can "feel cold" because the chairs, desks, walls are still cold and you body radiates (sinks) heat to them. Thus sometimes when folks turn the thermostat off or low; they raise the air way hotter than normal to feel ok.

One can too just read the gas meter to get an idea of the gas used.

**The savings by turning off/lower the heater get eaten away somewhat if one has to have it way hot in the morning; since the room items are all cold. Thus jacket is a solution in the morning!

 

[ronhic]

Ok...

...here is our experience with playing around with the thermostat here.

When we bought this house at the beginning of last year, it had been nearly 15years since I had lived in a house with forced-air central heating, so we played around a little.

From the beginning of winter (acknowledged in Canberra as 25th April - you DON"T dare turn central heating on before) we set the following...

Monday - Friday 19c (66F)
Morning 5.30 - 8.00
Evening 5.30 - 11.00

Weekend 19c
Morning 5.30 - 10.30
Evening 5.30 - 11.30 If we were home, we press 'hold' to ignore the timer, temp hold to boost to, say 21c (70F) if needed etc...and 'run programme' before we headed to bed to ensure it was back on programme...

Overnight it was set to 15c (59F)

The first winter gas bill was $950.00 (approx)

My other half nearly keeled over....even though we had been told that given the furnace is old and it was our first bill with central heating that this was low - many, according to one person I spoke to, experience nearly double that because they have expectations of how warm a house should be with central heating and start at 22-25c...

Anyway, we adjusted the operating times and temperatures. So, on a week-day morning, we moved it down to 17c (62.5F) and reduced the operation by an hour (or 40% time reduction) and in the evening, we reduced the temperature to 18c (64F) and shortened the time by an hour (or about 15%)...

Overnight we left the same.

Our next gas bill, still in winter was nearly $200 cheaper

Small adjustments can lead to big savings.....

 

[passatdoc]

I turned down the temp to 59 from 61 F last winter. I have a four cycles/day electronic thermostat with separate Sun and Sat cycles. I let the house go down to 54 F at night or during the day. At 5:45 am, it kicks on and brings the house to 59 F. It only heats to 59F from 05:45-7:30 in the morning, or at other times if temp goes below 54F

On my online gas bill, I can see usage from as far back as 24 months ago. The monthly therms on the January bill (reflects December usage) went from 28 two years ago to 20-21 for Jan 2010 and Jan 2011. My base, non heating usage in the summer months is 5-6 therms, usually 6 (hot water, cooking, clothes drying). So my heating use appears to have dropped from 28 - 6 = 22 therms in 2009 to 22 - 6 = 16 therms now and in 2010.

Of course, weather variables are not factored into this, but this year has been colder than most, with the heating season starting in early November, instead of early December. We did have a lot of rain last month, and on rain days the temperature is moderated by cloud cover. On clear nights, it gets down into the 30s here on a routine basis, whereas overnight low temp is 40s if there is rain. However, the thermostat change two years ago seems to have dropped usage on the January bill for two years in a row. [this post was last edited: 1/5/2011-17:20]

 

[3beltwesty]

electric

In my old California Apartment I had in Ventura County, to run the heater was rather expensive, 1 dollar per hour. It was electric; 240 volts, something like 50 amps. I typically just heated the bedroom with an electric space heater and never ran the central air heater.

If one came home to a cold apartment at 7pm, the main heater would run for hours to heat up the sheetrock and one would still feel cold. Thus if one was up to midnight watching TV; one might as well place 5 bucks in a jar to pay the bill. This was 25 years ago.

Thus at that time is was cheaper to turn the bedroom heater on at 7pm and go watch movie at a movie theater!

 

[suburbanmd]

The physics behind it

You have to heat your house because it loses heat through the walls and roof. Physics says the rate of heat loss is proportional to the temperature difference between inside and outside. A lower inside temperature means less heat is lost, therefore less fuel burned. Comparing a house kept at say, 65F for 24 hours/day, versus one kept at 65F for 16 hours/day and 55F for 8 hours/day: The latter loses less heat, and will have lower heating bills, regardless of the furnace working harder while it recovers the temperature. The exception would be if the furnace burned a more expensive fuel while it was working harder. For example, if you normally heat with a heat pump, but the resistance strips activate during the recovery time, that could reduce the savings or even eliminate them. In this case you'd have to run a more detailed analysis.

 

[frigilux]

I now keep my house at a constant 64 degrees during the heating season. I usually crank it up to 68 for a few hours when company comes, as most keep their houses warmer and are uncomfortably cold when they're at my place. My house was built in 1963, and is not well-insulated, so I get nervous about frozen pipes in the winter, when the outside temp is often anywhere from -10 to +10. We're supposedly getting super-cold air all next week from Canada (thanks, LOL!) and low temps may go down to -25 at night.

I should have insulation added to the attic. That was one of the suggestions when I purchased the house. The inspector said it could use another 4-to-6 inches of insulation. I can't do a lot about insulation in the walls until I can afford to replace my siding, which could be another 10 years. I'm shocked at how little insulation there is in the wall every time my dishwasher has been replaced.

My natural gas bill is on an "even-pay" plan, currently at $76 per month. I used to keep the house heated to 70-72 in the winter (which is common in this area), and my bill rocketed to $138 per month for a year or two. Then I decided to lower the house temp and after a couple of years I received a rebate check for $750, and my bill was adjusted to $76/month. I've just gotten used to the cooler temp.

 

[mrb627]

Old Game

I used to play the thermostat game with my hvac until I was told that it ultimately shortened the life of your equipment.  If you absolutely feel the need to swing temperatures in your home, no more than a 3 degree difference should be your rule.
​
​Malcolm

 

[jetcone]

I'm almost with Malcom on this

The "Doktahs'" have found the optimal sleeping temperature for humans is between 61-66 degrees. Anything below or above interferes with sleep rhythms.
So thats my starting point for a bottom temp.

I also feel and havent' worked this out yet but still feel this way:
Cycling huge swings in your heating creates huge burning cycles to catch up from a low temp. Think of a potters' wheel. You kick hard to get it going but once its turning it will always loose speed but if you give it frequent small kicks then it will combine with the momentum you started it with and keep going at a steady speed forever with little effort.

I think that the above cycle is true for typical swings in outdoor temperatures, when we hit 15 F here the boiler is working most of the night so its out the window with that.

All in all your best defense is tighter insulation and stopping air gaps.

 

[ronhic]

All in all your best defense is tighter insulation and stopp

This is very true....

...however, if you are renting, that may be impossible to achieve and if buying/owning, it could be too expensive.

In conjunction with trying to prevent draughts, I would also knock the top end temperature on the thermostat down a little...

 

[austinado16]

I don't play the thermostat game either

It takes less energy to keep the house at a constant tempurature than it does to heat or cool all of this thermal mass until it's comfortable again. We work in order to have money and enjoy a nice home, so saving $10 or $50 or $100/mo to enjoy it, doesn't make sense to us.

I've got a buddy and he and his wife play the "don't heat it and save money" game. If I go over there, he and his wife will be in knit hats and thermal-type hiking/backpacking gear, or heavy sweats. They sleep in sleeping bags, fully clothed, inside their bed. Both work full time and it's a 1,500sq.ft. track home with forced air. So for $100/mo, for 4 months, they could live in comfort. To me, living like that is just ridiculous....why work, and why have a home?

YMMV, of course.

 

[maytagbear]

I'd LIKE to turn the thermostat down

a few degrees, but the more I touch it, the more likely the furnace is to act up, so I set it once during the heating season, and leave it there!  When it was acting up regularly, I was turning it GENTLY down every night (64F), and GENTLY (68F) up every morning, and the thing was often in need of the landlord.  (Remember the locked basement?)

I'm on a billing plan with East Ohio Gas.

Lawrence/Maytagbear

 

[a440]

59 Has been my temp this winter. 
If company comes over it goes to up to about 63. 
My animals and I have been comfortable at 59. Each have a heated bed.
I have been able to control the humidity much better.  Good for my 3 pianos.
Big, HUGE savings on natural gas bill!
Brent

 

[qsd-dan]

59 Has been my temp this winter



I don't know if I could ever get used to that temp. Maybe if I was moving around, but I'd quicly freeze after sitting for a few minutes. 68F is the norm during the day. 60F for sleepy time.

 

[a440]

59 is great....

for cuddling.....

 

[112561]

Two of my indoor thermometers read 66.6 this morning

I try to keep the heat between 75 and 77 at the most. It's been colder in Florida longer for the first time in years. I have a twelve year old Goodman split system.

 

[DADoES]

Per discussions I've seen on other forums, energy usage and cost is always reduced by setbacks. It costs less not to run an energy-consuming device than to run it, seems reasonable to me. I did heating and cooling setbacks for years, but not so much now that I'm working primarily from home. I've been running 62°F as the "normal" heating temp for the last couple years, with a space heater in the bedroom/bath as needed, or sometimes an electric blanket. Last electric bill was $105, which includes running two computers 24/7, water well & aerobic septic system, etc. That's the full energy cost of the house, I have no natural gas or propane appliances.

 

[mrb627]

What?

59 degrees + stepping out of a hot shower? I would be sick all the time.

And sleeping in sleeping bags in my own bed? Sounds like camping all the time.

Malcolm

 

[a440]

59 is great


It is not uncomfortable to me at all.
In fact I turned up the heat the other day to about 63 when a friend came to visit. I thought I was going to smother!
Chilly Willy