Programmable or standard thermostat ?

[Hilltop Cycle ATV]

I have heard many theories on programmable thermostats . Some people say it is a gimic by the thermostat companies and actually do not save on your heating bills at all . And others say they save them alot of $ in energy bills. Has anyone ever done a personal study on their heating bills with a manual thermostat and then installed a programmable ? Did it actually save you $ ? I would like personal studies and observations or at the least a neutral study not perfomed by a thermostat company. Thanks, Raz

[trader4]

"I have heard many theories on programmable thermostats . Some people say it is a gimic by the thermostat companies and actually do not save on your

heating bills at all . And others say they save them alot of $ in energy bills. Has anyone ever done a personal study on their heating bills with a manual thermostat and then installed a programmable ? Did it actually save you $ ? I would like personal studies and observations or at the least a neutral study not perfomed by a thermostat company. Thanks, Raz "

It's virtually impossible for anyone to do a personal study because the environment is totally uncontrolled and you're looking at measuring a fairly small delta.

However, the physics are quite simple. The amount of heat loss is proportional to the temp difference. Cut the temp difference between inside and out by say 20% and you will use roughly 20% less energy to maintain the lower temp. Of course this new lower temp isn't reached immeadiately, so the heat loss to the outside will gradually decrease over a few hours until you reach the new lower temp.

There is no question that setting back the temp will save on your heating bills and is one of the easiest things to do. How much of a savings depends entirely on how much you set it back and for how long.

[DaveR]

A gimmick? It's really common sense.

A programmable thermostat is not magic. It eliminates the need to manually turn down the thermostat at times when it makes sense to do so, such as at night and when you go to work.

Energy bills aside, for the convenience factor alone, a programmable thermostat is a no-brainer.

[SQLit]

I agree with the other posters. My local utility has literature that basically says that if you can vary the temp for more than 8 hours and more than 5 F then you can save 10%. The real rub is your home, the temp outside and the time you can vary the temp. A really cold night and the set time in the morning may be to late to make the house warm in all areas. If you in a situation where some one is home all day then the set back will have limited effect.

Check localy with your utilities and see what they say. I have had set back stats for more than 20 years and would not be with out one.

[Bennett Price]

Why not try it for yourself. For a month simply set back your current thermostat to, e.g., 50F, whenever the house is empty or at night and see what your bill looks like. A programmable thermostat will do exactly the same thing but won't forget.

[trader4]

"Why not try it for yourself. For a month simply set back your current

thermostat to, e.g., 50F, whenever the house is empty or at night and see what your bill looks like. A programmable thermostat will do exactly the same thing but won't forget. "

And this is going to prove what? Right now, it's Dec, a month from now, it will be Jan, when the weather can be a lot different. Even cloudy vs sunny days make a difference. And what you're trying to measure is small compared to differences made by the weather, plus other factors that can vary.

[Christian Fox]

A study by Natural Resources Canada found that a setback of 16C during the day (when the house is usually empty) and overnight (while people are sleeping and under warm blankets) would result in a 13% savings in natural gas use over the heating season, with a setback of 18C resulting in a 10% savings. There was also a small (about 2%) decrease in electrical use, since the furnace fan isn't running as often. The full text of the study is here:

A programmable thermostat results in energy savings when you program it to turn down the heat for a long stretch of time, such as overnight or during the day if the house is unoccupied. You can achieve the same results with a standard (manual) thermostat, but only if you remember to turn it up and down all the time. Programmable thermostats just automate the process so that you don't have to think about it (and have the added benefit of raising the temperature _before_ you wake up or get home in the evening, so that you don't have to live with a chilly house while the furnace is doing its thing.

[Edwin Pawlowski]

Exactly why another poster said it was about impossible for Joe Homeowner to conduct real life tests. You need controlled conditions, like those the thermostat companies have the money to do. I guess you can use degree days as a guide, but that is not perfect either. Good enough for the oil companies to set deliveries though.

[Joseph Meehan]

There have been a number of test, including one in Columbus Ohio in a specially built home in the downtown area. They all have shown savings.

Now having said that there are a number of factors including local weather conditions, type of heat, (big difference between heat pump and resistance electric). Numbers are difficult to come up with, but in short, it works.

[Hilltop Cycle ATV]

The theory that I am thinking of is just this. Say during the night I turn the thermostat down 15 degrees for 8 hours. Then in the morning when the thermostat kicks back in it takes 4 hours to raise it back up those 15 degrees . Did I actually gain anything ? Or would keeping it the same temp save me $ ? Thanks, Raz

[SQLit]

It took me 2 years to get the managers at work to start using degree days for analysis of energy usage. In the beginning they were comparing Nov to Dec (example). Then they would pull a month and look at the history in the data base. The conclusions that they made were scary at best. Now that we have over 7 years of reliable data some conclusions can be drawn.

Your tax dollars at work.

[Edwin Pawlowski]

There have been some testing and curves published. IIRC the maximum savings is about 10 degrees. After that the recovery time starts to offset the savings.

Aside from the actual savings, there are the psychological factors. If the T'stat is programmed, there is less likelihood of others turning up at first sign of a chill. I have one zone that comes on in the AM, heats to 70 degrees, then drops to 68 after two hours. It is enough to ward off the morning chills and get you comfy while normal activities take over the rest of the day.

[CJT]

Since your average temperature is lower, average heat loss to the outside is also lower. That's your conservation.

Don't expect huge savings. Those come from making sure your ducts aren't leaking heated air into e.g. the attic, and that your furnace is running efficiently.

[Hilltop Cycle ATV]

Just got done installing the programmable thermostat I will see what it saves me. I noticed under the cover of the old thermostat that it had an adjustment that had a slide that said .2 - 1.0 , is that the adjustable range of temp. tolerance ? If so, it is set on .4 and my furnace cycled alot . I noticed that my programmable is factory set at 1 degree +/- . So, my fan won't be kicking on/off so much, I am hoping startup of the fan is costing me a little energy that I might get back over the years with it not kicking on / off so much. Am I right on the adjustment on the old one ? Is .4 kinda overkill ?

Thanks, Raz

[Joseph Meehan]

Yes. Think of heat as BTUs You add BTUs to warm up the house. BTUs are lost as heat leaves the house. The amount of heat that leaves the house or that your heating system adds back in is measured in BTUs. During the night those BTU's leak out around and though the walls and windows. When it is warmer inside more BTUs leak out because they are under more pressure. Allowing your home to get cooler means fewer have leaked out over night and those are the ones you need to replace to get back to were you were.

In short if it takes your furnace 4 hours to catch up and lets say it ran 2 hours during the night (total of 6 hours) then you know it would take more than 6 total hours of running the furnace overnight and during the next four hours to keep it at the regular temperature.

[mm]

Long before there were setback thermostats, my mother, and everyone who wasn't stinking rich, set the thermostat back every night before we went to bed. That's why it was always cold when I got up in the morning.

The advantage of the setback thermostat is not that it turns the heat down. It's that it turns it UP just before people have to get out of bed, and again before they get home from work. What used to happen is people would get home, and then they would turn up the heat. For 10,

20, maybe 30 minutes they were cold and they tolerated it to save money.

If you had ever had to stoke a coal furnace, you know first hand for certain that it saves not to make the house so warm when it doesn't have to be

In fact the notion that one has to warm the house, just for the time from 7AM to 8AM, when everyone leaves, is an example of how spoiled we are. We're all trying to live like rich folk, and then some complain about the cost of heating fuel.

Remove NOPSAM to email me. Please let me know if you have posted also.

[Edwin Pawlowski]

You have a coal stove for central heat? You are a rich bastard!

Yep, we are very spoiled compared to the centuries of life before the past

50 years or so.

[Christian Fox]

While the temperature drops in the evening, you don't need to heat the house as much (since the temperature will be dropping, the furnace won't run until the lower temperature has been reached). The energy saved during the temperature dropped is roughly the amount of energy you'll need to use to bring the house temperature back up to the daytime temperature when the thermostat is turned up again. The savings when the temperature is dropping are offset by the extra energy used when the temperature needs to be raised. While the temperature is at the lower value, though, you're saving money, since the difference between the indoor and outdoor temperatures is lower.

[Christian Fox]

The amount savings will vary depending on the outside temperature, efficiency of the furnace, and a whole load of other factors.

The bottom line, though, is that programmable thermostats, set correctly, will save money over the long term. I've also found that they can make the house more comfortable, since you can have the temperature a bit higher in the morning (to ward off the morning chills) but have it cooler overnight (most people find they sleep better if the room temperature is cooler).

[Anonymous]

You'll save ( heating ) money if you turn down the thermostat to 62 before you go to bed, then turn it up to 68 when you get up in the morning.

You'll save money if you turn down the thermostat to 62 when the house is unoccupied. ( ie everyone at work/school.) Then turn it back up when the first occupant gets home.

If you can remember to do it all the time, you don't need a programmable thermostat.

Else, go to Home Depot, get the $39.95 special, and install it yourself. ( 4 > 6 wires ) The only hard part is programming the ON/OFF times.

Yes, it'll pay for itself in a few months.