# Thermostat temp difference between heating/cooling

**URL:** <https://boards.straightdope.com/t/thermostat-temp-difference-between-heating-cooling/320082>\
**Category:** Factual Questions\
**Created:** [September 4, 2005, 7:34pm UTC](https://boards.straightdope.com/t/thermostat-temp-difference-between-heating-cooling/320082 "2005-09-04T19:34:49Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![LivingInThePast](https://avatars.discourse-cdn.com/v4/letter/l/e19b73/32.png) [@LivingInThePast](https://boards.straightdope.com/u/LivingInThePast)\
**Post date:** [September 4, 2005, 7:34pm UTC](https://boards.straightdope.com/t/thermostat-temp-difference-between-heating-cooling/320082/1 "2005-09-04T19:34:49Z")

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We have two of those standard round Honewell mechanical thermostats for heating and cooling (CT87), in two different areas of the house (two different heating and A/C systems).

When the heat is on, the temperature shown on the built-in thermometer is pretty close (about 2 degrees) to the thermostat setting.

But when the A/C is on, the temperature on the thermometer is 6 degrees or so lower than the thermostat setting. To get a room temp of 74 degrees, we set the thermostat to 80.

That’s true of both thermostats.

Any idea why and what we can do about it?

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**Author:** ![EnderWay](https://avatars.discourse-cdn.com/v4/letter/e/d26b3c/32.png) [@EnderWay](https://boards.straightdope.com/u/EnderWay)\
**Post date:** [September 4, 2005, 7:52pm UTC](https://boards.straightdope.com/t/thermostat-temp-difference-between-heating-cooling/320082/2 "2005-09-04T19:52:03Z")

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Mechanical thermostats are very inaccurate. I don’t know why their is a difference  
between the heat accuracy and the AC accuracy… but  
I would suggest just switching to digital thermostats. Cost is not a lot.  
About $40.00 per thermostat for a basic non-programmable one!