# Can I take batteries out of thermostat for a week? **URL:** \ **Category:** Factual Questions\ **Created:** [September 6, 2016, 1:13pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182 "2016-09-06T13:13:56Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![wolfman](https://avatars.discourse-cdn.com/v4/letter/w/a8b319/32.png) [@wolfman](https://boards.straightdope.com/u/wolfman)\ **Post date:** [September 6, 2016, 1:13pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/1 "2016-09-06T13:13:56Z")
So I’m going on vacation for a week, and obviously don’t want to waste AC on an empty house. I a really don’t want to reprogram the whole thing, so my plan is to just take the batteries out till I get back. Nothing is going to freeze in Sept, and it seems simple and obvious enough. Is there any reason that I’m over looking why that would be a bad idea? ---
**Author:** ![wolfman](https://avatars.discourse-cdn.com/v4/letter/w/a8b319/32.png) [@wolfman](https://boards.straightdope.com/u/wolfman)\ **Post date:** [September 6, 2016, 1:21pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/2 "2016-09-06T13:21:00Z")
And I misspelled “can.” :smack: I really need this vacation. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [September 6, 2016, 1:29pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/3 "2016-09-06T13:29:04Z")
Won’t taking the batteries out lose the settings anyway? Doesn’t it have a ‘vacation’ setting? What kind of programmable thermostat is it? I thought “cain” was just your accent 🙂 ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [September 6, 2016, 1:33pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/4 "2016-09-06T13:33:09Z")
If you’ve got a fancy programmable thermostat, there should be some kind of option to override the existing program (without having to tediously reprogram it). Look for a “hold temp(erature)” option or something like it, and just set it to a temperature high enough that the AC won’t kick in. Alternatively, turn the cooling/heating mode to off. Either one of those actions should prevent the program from operating the furnace or air conditioner without having to remove batteries or reprogram anything. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 6, 2016, 3:13pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/5 "2016-09-06T15:13:14Z")
> [@wolfman](#): > > So I’m going on vacation for a week, and obviously don’t want to waste AC on an empty house. I a really don’t want to reprogram the whole thing, so my plan is to just take the batteries out till I get back. Nothing is going to freeze in Sept, and it seems simple and obvious enough. Is there any reason that I’m over looking why that would be a bad idea? Every thermostat I have ever seen has an “off” setting. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [September 6, 2016, 3:39pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/6 "2016-09-06T15:39:10Z")
**Moderator Note** > [@wolfman](#): > > And I misspelled “can.” :smack: > I really need this vacation. Typo in thread title fixed. Enjoy your vacation. ---
**Author:** ![SmartAlecCat](https://avatars.discourse-cdn.com/v4/letter/s/67e7ee/32.png) [@SmartAlecCat](https://boards.straightdope.com/u/SmartAlecCat)\ **Post date:** [September 6, 2016, 3:46pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/7 "2016-09-06T15:46:25Z")
> [@beowulff](#): > > Every thermostat I have ever seen has an “off” setting. Sure, you could just turn it off, but removing the batteries will save $0.00000001 in battery costs by not running the thermostat for a week. ---
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [September 6, 2016, 3:47pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/8 "2016-09-06T15:47:49Z")
Why can’t you turn it “off”? Do you have the instruction manual? ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [September 6, 2016, 6:28pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/9 "2016-09-06T18:28:51Z")
The battery is usually there only as backup to hold settings/keep clock running during power interruptions. Normally thermostats run from (24V?) AC power from the furnace. ---
**Author:** ![ThisSpaceForRent](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thisspaceforrent/32/345_2.png) [@ThisSpaceForRent](https://boards.straightdope.com/u/ThisSpaceForRent)\ **Post date:** [September 6, 2016, 6:47pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/10 "2016-09-06T18:47:30Z")
I second the off switch …or vacation mode. ---
**Author:** ![troub](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troub/32/14802_2.png) [@troub](https://boards.straightdope.com/u/troub)\ **Post date:** [September 6, 2016, 7:21pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/11 "2016-09-06T19:21:02Z")
> [@Marvin\_the\_Martian](#): > > The battery is usually there only as backup to hold settings/keep clock running during power interruptions. Normally thermostats run from (24V?) AC power from the furnace. Nope. Certain ones do, maybe even a lot of them these days. But any system that was originally built for something like one of those round dial thermostats, or an old beige box with a slider thing on it, those don’t seem likely to have the “common” wire needed for constant power to an electronic thermostat. At least I haven’t yet lived in a house that had one (small sample size, I know). > [@](#): > > If you are replacing an old thermostat with a new digital thermostat, the electronics in these units may need yet another wire for a terminal labeled ‘C’. This terminal is for a common connection from the control transformer that will provide steady 24 volt power between terminal ‘R’ and ‘C’ to power the thermostat itself. > > If adding wires to your thermostat location is not possible, or very difficult, look for a thermostat that is battery powered which won’t require the terminal ‘C’ for operation. The obvious down side of this is that if the battery goes dead the thermostat will no longer function. [http://www.electrical-online.com/thermostat-wiring-explained/](http://www.electrical-online.com/thermostat-wiring-explained/) ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [September 6, 2016, 7:31pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/12 "2016-09-06T19:31:08Z")
> [@troub](#): > > Nope. Certain ones do, maybe even a lot of them these days. But any system that was originally built for something like one of those round dial thermostats, or an old beige box with a slider thing on it, those don’t seem likely to have the “common” wire needed for constant power to an electronic thermostat. At least I haven’t yet lived in a house that had one (small sample size, I know). > [http://www.electrical-online.com/thermostat-wiring-explained/](http://www.electrical-online.com/thermostat-wiring-explained/) The vast majority run off of 24VAC. That’s why the note you linked to says: > [@](#): > > If adding wires to your thermostat location is not possible, or very difficult, look for a thermostat that is battery powered which won’t require the terminal ‘C’ for operation. The obvious down side of this is that if the battery goes dead the thermostat will no longer function. ---
**Author:** ![troub](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troub/32/14802_2.png) [@troub](https://boards.straightdope.com/u/troub)\ **Post date:** [September 6, 2016, 8:11pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/13 "2016-09-06T20:11:26Z")
> [@beowulff](#): > > The vast majority run off of 24VAC. > That’s why the note you linked to says: They pretty much all do run off 24VAC, but do the “vast majority” have the C wire necessary to maintain constant power regardless of the cycle/relay positions? I didn’t take any wording in the article there to imply that, only that if you’re installing an electronic thermostat you “may need yet another wire,” and that if you don’t have it it might be relatively easy to add one. If you can’t add a wire, you have to go with batteries. The comment was “normally thermostats run from power from the furnace.” I still think, overall, it’s likely that the “normal” (non-electronic thermostat) setup is some kind of thermoelectric switch thing that trips a relay. Neither the dial nor the temperature switch really needed a power source to power themselves. In my previous house, I could replace the old round dial thermostat with a Nest by fishing up a C wire through the drywall with little difficulty. The thermostat wires in my current house squeeze out through a tiny hole in the plaster…who knows what’s behind there. I’m not messing with pulling any more wires through there, so I can only do batteries. Actually, in the previous house I did replace that dial with an electronic thermostat and battery power were the only options I ever remember seeing. I actually didn’t see any of this C-terminal business until they started getting touchscreens and WiFi and other cool stuff. I’m not convinced it was terribly common until a few years ago when it began to serve a purpose. I’m sure a professional HVAC person might have a better sense overall, though. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [September 6, 2016, 9:16pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/14 "2016-09-06T21:16:49Z")
I have a quite cheap digital thermostat. If I want the system off I can just set to the Heat-Cool switch to the middle position. When gone in the summer, I set the temp up a couple degrees and press “Hold”. I do _not_ want the AC completely off. Did that one time and the house got _way_ too humid. Thirdly, I have a master switch (looks like a light switch) on the furnace. This shuts it all down for service. Plus there’s the breakers on the circuit panel. Pulling the batteries is overkill. ---
**Author:** ![usedtobe](https://avatars.discourse-cdn.com/v4/letter/u/ec9cab/32.png) [@usedtobe](https://boards.straightdope.com/u/usedtobe)\ **Post date:** [September 6, 2016, 10:56pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/15 "2016-09-06T22:56:15Z")
You can: 1. input a “can never be reached” temp and press “Hold” 2. Turn the thermostat “Off”. 3. Unplug the thermostat from its clip-in socket/bracket (newer, digital units) I vote for option 2. See: “Heat/Cool/Off” switch. If you have a heat pump, the above may or may not apply. ---
**Author:** ![Mama\_Zappa](https://avatars.discourse-cdn.com/v4/letter/m/71e660/32.png) [@Mama\_Zappa](https://boards.straightdope.com/u/Mama_Zappa)\ **Post date:** [September 8, 2016, 4:47pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/16 "2016-09-08T16:47:46Z")
> [@Marvin\_the\_Martian](#): > > The battery is usually there only as backup to hold settings/keep clock running during power interruptions. Normally thermostats run from (24V?) AC power from the furnace. Some newer, fancier ones, not so much (I think). Ours definitely doesn’t behave right when the battery dies (and it’s a hella pain in the ass to get the front plate off to replace it - it was clearly designed by someone who used to design headlight replacement schemas for auto companies). Ours will not change temperatures or anything in that mode and for some reason I think the furnace ran constantly. To the OP: Depending on the weather where you live, why not just set it to 80 or so for heat, and/or 50 or so or cold. You don’t want the house to get too extremely hot or cold while you’re gone. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [September 8, 2016, 10:35pm UTC](https://boards.straightdope.com/t/can-i-take-batteries-out-of-thermostat-for-a-week/765182/17 "2016-09-08T22:35:54Z")
Seems like the OP has solved his ‘problem’ and gone off on his vacation.