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  1. #1
    Join Date
    Dec 2007
    Location
    Bucks County, Penna
    Posts
    181

    Cheaper to keep heat on or turn off?

    I'm finding conflicting answers to this, so I thought I'd go to you guys. Am I better off turning down my gas heat thermostat to 57 while I'm not home and turning it up to 70 while I am home.... or am I better off keeping it on maybe 62 while I'm away? Most days I'm only home about 4 hours before I head to bed and then I'd turn it back down to 57, so it's only keeping me toasty for those 4 hours. We've had plenty of 15-30 degree day time temps around here, so it's running all day no matter what. I'm in a 800 square feet house.

  2. #2
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,663
    Quote Originally Posted by AlmondEyes View Post
    I'm finding conflicting answers to this, so I thought I'd go to you guys. Am I better off turning down my gas heat thermostat to 57 while I'm not home and turning it up to 70 while I am home.... or am I better off keeping it on maybe 62 while I'm away? Most days I'm only home about 4 hours before I head to bed and then I'd turn it back down to 57, so it's only keeping me toasty for those 4 hours. We've had plenty of 15-30 degree day time temps around here, so it's running all day no matter what. I'm in a 800 square feet house.
    Turning it off saves.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  3. #3
    Join Date
    Dec 2005
    Posts
    114
    Have a honeywell t'stat installed!
    Bob O. 84,Pa.

  4. #4
    Join Date
    Aug 2009
    Posts
    1,127
    Quote Originally Posted by AlmondEyes View Post
    I'm finding conflicting answers to this, so I thought I'd go to you guys. Am I better off turning down my gas heat thermostat to 57 while I'm not home and turning it up to 70 while I am home.... or am I better off keeping it on maybe 62 while I'm away? Most days I'm only home about 4 hours before I head to bed and then I'd turn it back down to 57, so it's only keeping me toasty for those 4 hours. We've had plenty of 15-30 degree day time temps around here, so it's running all day no matter what. I'm in a 800 square feet house.
    You will save money, I do the same thing. Consider turning it down while you are sleeping as well. If you have a regular schedule and a programmable stat, you can have it all the way back up when you get out of bed.

    I'm still figuring it out myself, but usually I am turning it down to 58 when I'm gone and when I'm sleeping. If I'm only going out for a while, I don't turn it down as much. I currently have a manual stat, but also have great air supply to my very small bathroom. So when I turn it on in the morning, hop it the shower, my bathroom is toasty much quicker than the rest of the house. So that is working well for me currently (about to do a furnace changeout).

    Most stats bottom out at 40, and most likely even settings that low is safe for your pipes. Some will say that large temperature swings can damage your house, not sure I buy that. Last winter I drained the pipes and turned everything off, no signs of issues when I returned in the spring. Lots of folks winterize their home every winter.

    The more you turn it down, the lower your gas costs. It is more a question of your recovery time and how long you can wait to bring it back up to temp. Living in a small house has some advantages. Your furnace is oversized (as they are in virtually all small homes with forced air gas), which means that recovery from a setback is very fast.

  5. #5
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    1,629
    It will save more money to do some caulking and insulating. Shouldn't be any reason for your house temp to fall that low in a few hours let alone fall 13 degrees and the furnace still runs all day.
    Nothing special about our little house and it drops from 73 to 69 in a typical 10 hour work day.

  6. #6
    Join Date
    Nov 2008
    Location
    Chapel Hill, NC
    Posts
    1,070
    Heat loss is proprtional to temperature in your house (actually the difference between the indoor temperature and the outdoor temperature). So the higher the indoor temperature, the greater the heat loss. Keeping your house at 70 will produce a higher heat loss than 70 at night and 60 during the day. The greater the heat loss, the more heat you have to provide ($$$) to keep the house at the set temperature.

  7. #7
    Join Date
    Jul 2006
    Posts
    88
    Quote Originally Posted by AlmondEyes View Post
    I'm finding conflicting answers to this, so I thought I'd go to you guys. Am I better off turning down my gas heat thermostat to 57 while I'm not home and turning it up to 70 while I am home.... or am I better off keeping it on maybe 62 while I'm away? Most days I'm only home about 4 hours before I head to bed and then I'd turn it back down to 57, so it's only keeping me toasty for those 4 hours. We've had plenty of 15-30 degree day time temps around here, so it's running all day no matter what. I'm in a 800 square feet house.
    Good question...This is sorta like the question, "Does my air handler save on utilities if I leave the fan on constant or allow it to run only during cooling or heating?"

    A couple things come into play hear.

    1)What type of equipment do you have. (EX:heatpump, gas, etc)
    2)Is your house well insulated.

    In regards to the first point. If you live in a colder climate and use electric heat w/your heatpump then I would recommend that the thermostat be set back only slightly from your normal comfort point. This is because at most, a traditional heatpump w/electric aux heat is only going to distribute around 105DEG F. This means longer run times to warm the space back up and longer=more energy consumption. On the other hand, if you you oil, or gas heat your run time will be cut almost in half b/c these heat sources will supply around 120-130DEG F to the space which will heat up the area much quicker...So it is more efficient in fact to set your temp back a littler further IF YOUR HOME IS WELL INSULATED.

    In regards to the second point. Well...I would never recommend much of a set back because it will take so much longer for your system to bring the space back up to the normal setpoint and in so doing will consume alot more of your utilities. And with a poorly insulated home you also have to consider your furniture, walls, etc which will in effect demand a higher heat load from your system as these item's temperature will equalize to whatever your setback temperature is and therefore will "soak" up alot of heat in order to equalize with the increasing space temp as the system tries to reach the normal comfort setpoint.

    WOW...talk about a run on sentence. Anyways...there is quite a bit of science to back that up however I would prefer to keep it short and sweet.

  8. #8
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,692
    a 3-5* setback is optimal, wetting it back 10-15* is well stupid, what you save by shutting it down you will spend warming your content and walls back up.

    If you are gone for a few day's 10* setback is good

  9. #9
    Join Date
    Apr 2009
    Location
    Central New Jersey
    Posts
    253
    The longer and lower you set back your theromstat, the more energy you will save if you have something other than a traditional heat pump with auxillary heat strips.

    The idea you use more enegy to recover from a 10 degree versus a 5 degree set back because it take longer to heat up the mass inside your house makes no sense. The heat loss is faster when the temperature is higher. Your house is constantly losing heat which your furnace must supply.

    I do agree a 10 degree set back may be impractical because the recovery time is long. This is the primary reason to limit the amount of the set back. It is not because a larger set back wastes energy.

  10. #10
    Join Date
    Jul 2006
    Posts
    88
    Quote Originally Posted by mike_home View Post
    The longer and lower you set back your theromstat, the more energy you will save if you have something other than a traditional heat pump with auxillary heat strips.

    The idea you use more enegy to recover from a 10 degree versus a 5 degree set back because it take longer to heat up the mass inside your house makes no sense. The heat loss is faster when the temperature is higher. Your house is constantly losing heat which your furnace must supply.

    I do agree a 10 degree set back may be impractical because the recovery time is long. This is the primary reason to limit the amount of the set back. It is not because a larger set back wastes energy.
    I will Kindly disagree.

    Again it really revolves around the two points listed in my previous post. If you are away on vacation for a week or so then YES definitely setting your thermostat back will save you $$$......but if you have to come home 5-7 days a week and force your system to recover from a 10-20 degree temperature difference, especially in a poorly insulated home, that is going to cost you $$ not save $$. Keep in mind..your asking the system to recover from a temperature difference FIVE TO SEVEN days a week. The system wasn't designed for recovering from such a huge heat loss but was rather designed to maintain a comfort level.

  11. #11
    Join Date
    Jul 2006
    Posts
    88
    In addition...when you are recovering from such a temperature difference if you have multiple stage heat...more than likely all stages of you heat will be running at first and then slowly knock off the closer to setpoint you get. This initial huge consumption of utility will be costly when you are doing it FIVE TO SEVEN TIMES A WEEK.

    In the vacation scenerio you are only asking your system to do it once....after you return....and yes there are smart recovery algarythmms built into many tstats today but you are still recovering.

    Your heating and cooling systems are designed to maintain comfort levels NOT recover.
    Your system is forced to operate in a underdesigned condition when you allow your home temperature to drop so far from what your home comfort level is normally.

  12. #12
    Join Date
    Apr 2009
    Location
    Central New Jersey
    Posts
    253
    Maybe I have misunderstood your point. Are you saying you won't save money because you will stress your furnance each day by trying to recover from a large set back and eventually have to pay the money in added repairs? Or are you saying you will expend more energy trying to recover from a larger set back each day?

  13. #13
    Join Date
    Jul 2006
    Posts
    88
    Quote Originally Posted by mike_home View Post
    Maybe I have misunderstood your point. Are you saying you won't save money because you will stress your furnance each day by trying to recover from a large set back and eventually have to pay the money in added repairs? Or are you saying you will expend more energy trying to recover from a larger set back each day?
    Well...both actually and this will increase or decrease depending on the home's R value.

    If your system is working "overtime" 5 -7 times a week to recover from a 10-20 deg setback than yes it will shorten your system life expectancy.

    AND

    If your system is working "overtime" 5-7 times a week to recover from a 10-20 deg setback than yes you will be spending alot of $$ compared to simply maintaining a realistic and practical setpoint. Your system is designed to maintain and if your home is tightly insulated it will run very little...much less...than the amount of time it would total after 5-7 recovery cycles.

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