What Temp to Keep House while Away?

[Mr. Brass Bonanza]

When planning on being away during the cold season, how low of a temp is safe to keep the house if there are no animals and no plants? We plan on being away for a few days and will have a thermometer in the back window for a neighbor to keep an eye on just in case the heat goes off, but with no living creatures in the house during that time, couldn't we keep it rather low? Is, for instance, 58 too low?

Thanks!

[Dulcee]

We're in NC but we usually set it at 50 (in the winter) if the pets are with us.

[gerald72]

50 should be fine.
Just don't want pipes to freeze.

[TheDuckRocks]

Last January I left our temp set in the low/mid 50s range while we were in WDW. My electric bill to get the house back up to normal temp was outrageous. It would have been less if I would have left the darn thing at the regular temp that we run during the cold winter months. We just got back from a trip this winter and left the temp about half way from normal to the 50s. I will see what my electric bill is next month. Keeping my fingers crossed. BTW we live in WV.

[dnickels]

Last January I left our temp set in the low/mid 50s range while we were in WDW. My electric bill to get the house back up to normal temp was outrageous. It would have been less if I would have left the darn thing at the regular temp that we run during the cold winter months.

The laws of thermodynamics would disagree with that. (I don't mean to pick on you, but as an engineer I see people claim this and it drives me crazy).

It is - always, 100% of the time, for as long as the laws of the universe have been and will continue to exist - the case that setting the temperature low while you are gone and then raising it back to normal uses less energy than keeping it at the normal temperature while you are gone (in a cold climate of course).

Set it at 50-55 and it's always a good idea to open up the cabinets where pipes are (i.e. under the sink) just as an extra precaution.

[princessgirls]

I just leave it at 60...like it is when I'm home...mostly...LOL!

Julie:mickey:

[joonyer]

We have a family cabin that we close up for months at a time, winter included. We turn the water main off, open the faucets so there's no pressure in the pipes, and then turn the heat completely OFF. Many times it gets down below freezing inside the house.
But guess what? with no live plants or animals inside, nothing happens. Furniture and appliances don't care if it's below freezing. And we use ZERO energy to keep the place warm when we are not there.
When we arrive to use the place, even in the dead of winter, we turn on the central heat, set it to 65 and within about 30-45 minutes, the place is warm.

Bottom line, if you keep your pipes from freezing, it really doesn't matter how cold the house gets.

[TheDuckRocks]

The laws of thermodynamics would disagree with that. (I don't mean to pick on you, but as an engineer I see people claim this and it drives me crazy).

These are the amounts we paid last year for our electric bills:
2 months before - $139.75
month before - $143.75
month that covered the time when we reheated house after trip - $200.75
the following month (still winter temps) - $148.75
hooray, spring has arrived - $135.75
There could have been some other reason for the bump of 25% in the bill for that month, but I have no idea why. No extra people in the house. No increase in water usage from the water company, which might reflect for heating water. No repairs for anything connected to the electrical system.:confused:

[BrerGnat]

The laws of thermodynamics would disagree with that. (I don't mean to pick on you, but as an engineer I see people claim this and it drives me crazy).

It is - always, 100% of the time, for as long as the laws of the universe have been and will continue to exist - the case that setting the temperature low while you are gone and then raising it back to normal uses less energy than keeping it at the normal temperature while you are gone (in a cold climate of course).

Set it at 50-55 and it's always a good idea to open up the cabinets where pipes are (i.e. under the sink) just as an extra precaution.

The issue is how electric companies charge for usage during different times of the day. If your heater has to run continuously during peak hours to reheat the home, it can and DOES end up costing more than if you left it on at a modest temperature while away from the home.

This has been our experience here both during the summer and winter months after vacations. This year in August we left our dog home with pet sitter coming twice a day. Consequently we left our AC at 75. We usually turn it off when we go on vacation. Our bill was significantly lower for August than it was the previous year when we turned off the AC and then had to run it almost nonstop for 2 days to get it back down to a reasonable temp.

[joonyer]

. . . Our bill was significantly lower for August than it was the previous year when we turned off the AC and then had to run it almost nonstop for 2 days to get it back down to a reasonable temp.

How hot was your house?
Unless it was 150 degrees or something, if your AC took two full days of continous running to cool your home, then it is not very efficient. It shouldn't take more than a couple of hours to lower it to a comfortable temperature, unless your house is huge and your AC system is way too small, or your house isn't properly insulated.

[BrerGnat]

How hot was your house?
Unless it was 150 degrees or something, if your AC took two full days of continous running to cool your home, then it is not very efficient. It shouldn't take more than a couple of hours to lower it to a comfortable temperature, unless your house is huge and your AC system is way too small, or your house isn't properly insulated.

LOL. All of the above? Our home is 3100 square feet with just one smallish AC unit. Our indoor temp got to 91. It ran for 2 days and only got down to 78.

This home is also fairly poorly insulated. It was built in probably a couple months during the housing boom in 2005/2006.

We just rent it though, so nothinh we can really do about it. :)

[DizneyRox]

Personally I wouldn't trust 50°

Using simple maths, if it's 50° inside the house and 30° outside, the walls (where the pipes be) could be 40°. If it gets down to 20°outside, you're wicked close to freezing and below 20° I think you've got a good chance of freezing. When living in a house, the water moving in the pipes helps.

It was in the single digits in your neck of the woods just a few days ago.

I did the whole shut things off for vacations, but it was a pain to start back up. For only a few days, I wouldn't even bother. You're just asking for trouble to save a couple bucks in fuel.

[Scar]

Just an added thought...

If you close the main (takes about 10 seconds, and should be turned every year or so anyway,) if there just happens to be a leak while you're away, you won't come home to a flooded basement.

[Goofy4TheWorld]

The laws of thermodynamics would disagree with that. (I don't mean to pick on you, but as an engineer I see people claim this and it drives me crazy).

It is - always, 100% of the time, for as long as the laws of the universe have been and will continue to exist - the case that setting the temperature low while you are gone and then raising it back to normal uses less energy than keeping it at the normal temperature while you are gone (in a cold climate of course).

Well, in the real world the Law of Thermodynamics is only a peace of the puzzle, you are forgetting the law of how Heat Pumps actually work, which makes your statement false.

It is entirely possible that it can cost MORE money to re-heat a house that has been allowed to fall down to 50 degrees and then raised back up into the 70s, all depending on a variety of real-world factors including length of time at 50 degrees, the air tightness of the home, as well as the condition/heath of the home’s heating system.

If the previous poster had a heat pump in West Virginia, that heat pump is very efficient at maintaining a home at 72 during most hours of the day, but if the house is allowed to fall into the 50s and then run back into the 70s, the home's thermostat will, in it a desperate attempt to heat the house back up, switch on the backup "strip heat" which allows the home to heat back up much quicker and not run the heat pump to death as well. The catch is that "strip heat" is the least economical source of heat ever invented; it does a great job heating things up fast (just like your oven or hair dryer) but wastes a lot of energy in the process.

If the previous poster had raised the thermostat up no more than 2 degrees at a time, allowing the heat pump time to warm the house back up before triggering the strip heat (which comes on automatically when there is a greater than 2 degree difference between expected temperate and actual temperature) then their bill would have been cheaper, but if they jumped the thermostat straight from 50 to 70, they paid out the nose to heat the place back up.

[PopPhan]

Well, in the real world the Law of Thermodynamics is only a peace of the puzzle, you are forgetting the law of how Heat Pumps actually work, which makes your statement false.

It is entirely possible that it can cost MORE money to re-heat a house that has been allowed to fall down to 50 degrees and then raised back up into the 70s, all depending on a variety of real-world factors including length of time at 50 degrees, the air tightness of the home, as well as the condition/heath of the home’s heating system.

If the previous poster had a heat pump in West Virginia, that heat pump is very efficient at maintaining a home at 72 during most hours of the day, but if the house is allowed to fall into the 50s and then run back into the 70s, the home's thermostat will, in it a desperate attempt to heat the house back up, switch on the backup "strip heat" which allows the home to heat back up much quicker and not run the heat pump to death as well. The catch is that "strip heat" is the least economical source of heat ever invented; it does a great job heating things up fast (just like your oven or hair dryer) but wastes a lot of energy in the process.

If the previous poster had raised the thermostat up no more than 2 degrees at a time, allowing the heat pump time to warm the house back up before triggering the strip heat (which comes on automatically when there is a greater than 2 degree difference between expected temperate and actual temperature) then their bill would have been cheaper, but if they jumped the thermostat straight from 50 to 70, they paid out the nose to heat the place back up.

Thank you for that explanation. I work for a major HVAC manufacturing/engineering company and you gave an excellent accounting for how heat pumps do their jobs. We actually suggest no more than a 3 degree differential - and that includes using programmable thermostats for daily changes.

[Scar]

Heat Pump? When Kay said her electric bill went up, I assumed she had electric heat. If she has gas or oil, I would think the savings on that would well outweigh any electricity a pump would use.

[dnickels]

:Sigh:

Since multiple people have mis-stated my reply, I will reiterate that my statement involves the amount of ENERGY used, not COST. Yes of course you can come up with odd scenarios if you re-warm the house using inefficient heat sources or highly priced energy as compared to the normal baseline methods.

The science is not exactly complicated. The longer you maintain a large temperature differential the greater amount of ENERGY will be needed to maintain that differential. I could go on but I don't see much of a point if people are going to mis-interpret what I said.

OP: Most recommendations will tell you that 50-55 should be fine unless you have pipes in areas that get especially cold like a partially warmed entry-way or something. Set it at 55 and have a nice trip. :)

[Scar]

Even if you hadn't said you were an engineer, I would have guessed that. ;)

I say that having known, and respect, many engineers.

[dnickels]

Even if you hadn't said you were an engineer, I would have guessed that. ;)

I say that having known, and respect, many engineers.

It's both a blessing and a curse at times as you have probably observed. :)

[Goofy4TheWorld]

:Sigh:

Since multiple people have mis-stated my reply, I will reiterate that my statement involves the amount of ENERGY used, not COST. Yes of course you can come up with odd scenarios if you re-warm the house using inefficient heat sources or highly priced energy as compared to the normal baseline methods.

The science is not exactly complicated. The longer you maintain a large temperature differential the greater amount of ENERGY will be needed to maintain that differential. I could go on but I don't see much of a point if people are going to mis-interpret what I said.

OP: Most recommendations will tell you that 50-55 should be fine unless you have pipes in areas that get especially cold like a partially warmed entry-way or something. Set it at 55 and have a nice trip. :)

Nobody mis-stated your reply, you quoted TheDuckRocks post, even underlining the part about "It would have cost less...", within the context of a statement about COST, not ENERGY.

Further, the realities of a heat pump's use of strip heat for recovery heating, or an electric company's use of demand billing, are not "odd scenarios", but are everyday realities that people face when dealing with the cost of their energy used, not the theory behind it.

[TheDuckRocks]

Thank you all for the info about heating a house. I have learned a lot.
Just a little more for those of you who have been following these posts. Our house is all electric. It also runs with a heat pump system. I just verified both of these statements from documents provided from the home builder.
Not being an engineer nor someone who really has much understanding of the concept of heating a house, other than to turn the thermostat to the temperature I want, I am very serious that my understanding has increased.
As a retired accountant who still loves spreadsheets, I'm looking at the whole heating issue on a dollars and cents basis. The info about not going over changing the temp only 2 degrees at a time and keeping general change to a minimal amount will help me with lower electric bills this winter.:thumbsup:

[1DisneyNut]

:Sigh:

Since multiple people have mis-stated my reply, I will reiterate that my statement involves the amount of ENERGY used, not COST. Yes of course you can come up with odd scenarios if you re-warm the house using inefficient heat sources or highly priced energy as compared to the normal baseline methods.

The science is not exactly complicated. The longer you maintain a large temperature differential the greater amount of ENERGY will be needed to maintain that differential. I could go on but I don't see much of a point if people are going to mis-interpret what I said.

OP: Most recommendations will tell you that 50-55 should be fine unless you have pipes in areas that get especially cold like a partially warmed entry-way or something. Set it at 55 and have a nice trip. :)

I am also an engineer and will give my two cents worth. As others have already pointed out, there is a flaw in your original response. You are of course completely correct in your assertion it should take less energy to heat a house back up rather than maintain a consistent temperature. However, the problem is the type and efficiency of the heat producing equipment.

If the home had a heating unit that had only one way of producing the heat such as a gas furnace, oil heat, etc. then it would always 100% of the time use less energy and therefore cost less to heat the house back up rather than maintain the consistent temperature as you stated. This is because the efficiency of the unit is always consistent. On the other hand, as has been pointed out, heat pumps kick into "emergency heat" mode when they fall behind more than usually 3 to 5 degrees which uses extremely less efficient electric heat strips. The heat strips are basically a big version of one of those cheap plug in electric heaters where the wires glow red that you can buy at walmart.......extremely inefficient. This causes the heat pump to typically use 25 to 40% more energy while trying to bring the house back up to temperature whereas it would have been extremely efficient (more efficient than aforementioned gas and oil furnaces).

Depending on various factors including the outside temperature, SEER rating (efficiency) of the heat pump, R-value insulation of the home, thermal efficiency of the windows, etc. it could take 2 weeks or even more than a month of the heat pump being set at 50 for it to overcome the energy loss due to inefficiency of the heat strips while trying to recover.

Long story short, if it is going to be below 45 outside and you are going to be gone less than 2 weeks, only drop the temperature setting about 3 degrees and you will save a slight amount of energy and cost. It will also help save if you wait until night after the electricity rate has dropped to night rate before you raise the temperature back up assuming your electric company uses variable demand rates but that is also not a given. If the temperature is drastically colder at night, your unit may have to use the heat strips to recover and it would have been cheaper to raise the temperature back up during the day on the higher demand rates. When it comes to heat pumps, there is a lot more at play than simple thermodynamics.

[Tekneek]

When the air conditioning is on, I set it at 85. When the heat is on, I set it at 55.

[MIKESMOM]

I live in Maine,so our temps are similar to yours. I heat my home using oil, we have forced hot air. When we are away we turn our electric hot water heater off, and turn our heat down to 50.I open the cabinet doors under the sink just as a precaution. We have never had any problems even when the temps have gone down in the negative range while we were away.

[HollyB]

We are currently in the deep freeze here in Illinois. All the media outlets are running stories on how to prevent pipes from freezing. General consensus is to set your heat no lower than 55 degrees, leave sink cabinet doors open, and allow your faucets to drip a little--about once every 10 seconds. If there is low risk of power outage (i.e., you aren't expecting major storms while you are away), you can likely skip the dripping.