Energy Question for Engineers
- Thread starter Railroad
- Start date
Baja28
Obama destroyed America
Depends on the amount of swing but keeping it at the same temperature is most economical.
You could lower your T-stat a couple degrees during the winter when no one is home with no ill effect but any more (than a couple degrees) allows everything (walls, floors, ceilings, furniture, etc.) to cool off, then it requires more energy to re-heat them. Same principle with air conditioning, a couple degrees is fine but no more.
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itsbob
I bowl overhand
Scotty says keep your lithium crystals fresh and your HVAC will give you all she's got.
itsbob
I bowl overhand
I JUST remembered that and was going to go back and edit if nobody had caught the mistake yet.. TOO late!!
Railroad
Routinely Derailed
I JUST remembered that and was going to go back and edit if nobody had caught the mistake yet.. TOO late!!
C
czygvtwkr
Guest
Your A/C and or heatpump just move the heat around. The cooler it is outside the more efficient your A/C is, so if you can live with it cooler in the night and let things warm up a little during the hottest part of the day then that will be the most efficient use of your air conditioner, also if the air conditioner is shaded that will help too.
Railroad
Routinely Derailed
bcp
In My Opinion
I JUST remembered that and was going to go back and edit if nobody had caught the mistake yet.. TOO late!!
Thats a pretty big mistake when you have a clingon up your ass and you need massive thrust to get away.
Tilted
..
Are we talking about, rather than leaving the temperature set at a constant 72 degrees (e.g. when it's cold outside), setting it to maybe 62 degrees when you're gone and 72 degrees when you're home OR setting it to maybe 62 degrees when you're gone and 82 degrees when you're home? If you're referring to the former, which is what I'd assume, then it would use less energy to set the temperature down when you're gone for a while or don't need the heat set as high. In other words, setting it to 62 degrees starting when you leave for work and to 72 degrees starting when you return home from work will use less energy than leaving it set to 72 degrees all day long will.
The main reason for this relates to the basic laws of thermodynamics: Heat transfer is a function of temperature difference. That's why you're more likely to develop hypothermia in 40 degree water than you are in 60 degree water, and why you might wear a coat when it's 30 degrees outside but might not when it's 60 degrees.
Both unwanted heat loss and unwanted heat gain are increased when the temperature of the conditioned area is more higher than the surrounding environment (e.g. during the winter) or more lower than the surrounding environment (e.g. during the summer). If the temperature inside a house is 60 degrees while it is 50 degrees outside, the house will lose less heat energy than if the temperature inside the house is 70 degrees while it is 50 degrees outside. The amount of heat energy needed to heat a house to 70 degrees from 60 degrees will be less than the amount of extra heat energy that would have been needed to keep the house at 70 degrees rather than 60 degrees for the preceding 10 hours.
There's also the issue of heating / cooling unit efficiency, but that's a less definitive effect and - depending on your system - won't necessarily have a significant impact. But, at least for some systems, they are more efficient (i.e. in terms of the amount of heat energy injected / removed relative to the amount of electricity used) after they've been running for a few minutes than they are when they first come on. So, they are more efficient when they come on for 15 or 20 minutes to warm the house up or cool it down than they are when they are coming on for 3 minutes at a time to maintain a temperature.
As I hinted in the first paragraph though, if changing the temperature means sometimes setting the heat higher (e.g. when it's cold outside) than you otherwise would have to make up for having set it down at other times, then the situation is much different.
Tilted
..
Though I've heard this myth repeated a number of times, it is mistaken. Many people may find it more comfortable or convenient to leave the temperature at a set level. That's all fine and good (I typically leave mine at a set temperature). But if we're only talking about what is more energy efficient - what will result in less overall energy use - then that would be to set it down some in the winter (or up some in summer) when you aren't around or don't need the heating (or cooling).
Vince
......
I just keep my house at a constant temp. Takes more energy to cool a house down or heat it up then it would to keep it at a constant temp all day. :shrug: JMO But the folks that install the heating systems will tell you the same thing.
C
czygvtwkr
Guest
It would depend on the amount of time we are talking, if your going away for a week it is definately more efficient to keep the heat/air from running during that week than it would be to heat/cool the house. However while your at work or asleep it would depend on the level of insulation and thermal mass of your house. The greater the amount of thermal mass/insulation the longer it takes your house to change temperature so a house that has a high thermal mass and is well insulated would be more efficient to keep at a constant temp than one that isnt.
This is not a simple question with a simple answer. For the real answer you would have to know
1) Thermal mass of your house
2) Heat loss/gain coefficient of your house
3) The outside temperature
4) The temperature you wish to keep your house
5) The temperature you are willng to let it reach if you decide to let the temp swing
6) Some more complicated things like is it sunny, how much of the day is the sun on your house, what is the emissitivity of your house
It could turn out for house A its more efficient to let it maintain the desired temp, but for house B its more efficient to let the heat/air go off at night and while your at work.
I did all my graduate work in heat transfer and thermodynamics, but still I just keep my thermostat at a constant temperature (78 in summer, 68 in winter and usually off in the spring and fall) because thats what i like.
struggler44
A Salute to all on Watch
This and the efficiency of your system has the most effect on the cost of usage