A thermostat set at 72 that shows 75 is either reading wrong or not keeping up. Check a separate thermometer, the batteries, sun on the thermostat, the air filter, the ducts and the refrigerant, and call a pro if it persists.
If your thermostat is set at 72°F but the room reads 75°F, either the thermostat is reading wrong or your system is not keeping up. There are several possible reasons.
As I came across this issue myself, I’ve done a lot of research to find out the real cause of it.
While a lot of tutorials show useless steps that might waste your time, I prepared 6 ways to find out the real reason behind the difference.
Without any further ado, let’s get into it.
6 Ways To Find Out Why Your Home Doesn’t Reach The Temperature You Set
Inspect the thermostat
A thermostat that reads wrong can have a failing sensor, but it can also just be in the wrong spot, so check the other causes too.
The good thing is that it’s very easy to find out if this is the case.
You’ll have to use a separate thermometer to check if it’s showing the same readings.
If sensors are broken, you’ll have to buy a completely new thermostat.
If you do need a new one, a smart thermostat such as Google Nest is one option.
Check the battery
Thermostats are often powered by batteries, so it’s a smart idea to check the battery’s life.
Most modern thermostats will notify you when the battery is low, but some older models don’t have this feature.
Simply buy new batteries and put them into your thermostat. On a Honeywell, our Honeywell thermostat reset guide lists the batteries common models take.
If it shows different readings (accurate this time), then the issue was in the batteries themselves.
Inspect the power source
There are a lot of models that aren’t powered by batteries, and they use electrical systems inside of your home.
It’s time to check for tripped circuit breakers or any faulty fuses.
If you notice anything unusual, you should call an electrician to solve it for you. Once you’ve done it, your thermostat should start giving accurate readings.
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Change the placement
Try changing the position of your thermostat as readings can often be impacted by external factors.
For example, if it receives a lot of sunlight – it will show a higher temperature.
On the other hand, if it’s positioned in a cooler and darker area – it might show a lower temperature.
Always seek to position your thermostat somewhere in the middle, where it’s not too hot or too cold.
If you have a thermostat that’s powered by an electrical system, you should seek professional help in moving the thermostat.
However, if you plan to do it on your own – here’s an in-depth thermostat wiring guide that will help you.
Examine your HVAC
HVAC problems can also keep your home from reaching the temperature you set.
Sometimes you might have dirty air filters which push your AC to work hard to reach 72 degrees, and dirt and dust inside of those filters might be blocking the airflow.
Check your filter every month and change it at least every 3 months, according to ENERGY STAR. If you have a washable filter, clean it on the same schedule.
The first step is to simply clean the filters.
If you notice any change in temperature readings once you’ve done it, then you should buy new filters.
Another issue within the HVAC system could be ductwork.
Ductwork can usually have air leaks which lose a lot of air and it forces your unit to work harder while not being able to reach a certain temperature.
Additionally, a heat pump that is not working properly can cause the same problem.
When you notice that your bills increased suddenly, it might be time to inspect the ductwork inside of your unit.
Refrigerant leaks
Although this doesn’t happen often, it still happens from time to time and it’s worth taking into consideration.
An AC does not use up refrigerant, so low refrigerant means a leak, and the system will cool poorly.
Ice on the refrigerant lines or the outdoor unit can point to a refrigerant leak, but a dirty filter or blocked airflow can cause it too. Turn the system off, let the ice melt, check the filter, and call a technician if it comes back.
This is a serious issue, so seek professional help before doing it on your own.
How Do You Know If A Thermostat Is Working Properly?
The easiest way to check if your thermostat is working normally is to check if it reacts to any changes immediately.
Let’s say you’ve made some changes to the thermostat and if it doesn’t apply them immediately – it’s most likely faulty.
Also, a faulty thermostat can’t turn on your AC or furnace.
Another visible sign of a problem is if you turn off your AC and it still keeps working. That points to the thermostat or its wiring and needs to be checked.
This doesn’t happen simply because of the thermostat, but because of incorrect calibration, broken sensors, and bad wiring.
How Much Does It Cost To Replace A Thermostat?
It all depends on the issue and your location.
If you need a complete replacement and installation, Fixr’s 2026 estimate is $85 to $300, averaging about $200, depending on the type of thermostat.
Wiring work or a smart thermostat can push the cost toward the top of that range, so it’s important that you notice any issues from the get-go. If you need an HVAC professional to handle your installation, you can contact local contractors here.
If you decide to replace it, here is one smart thermostat to consider 👇
Best Smart Thermostat: Google Nest Learning Thermostat (4th Gen)
Google Nest Learning Thermostat (4th gen) with Nest Temperature Sensor
We earn a commission if you buy through this link, at no extra cost to you.The fourth-generation Nest Learning Thermostat shows the room temperature, learns your schedule and can be controlled from the Google Home app or by voice.
This bundle includes a Nest Temperature Sensor, which is the fix for a thermostat that reads a different temperature from the room you sit in: put the sensor in that room and the thermostat follows it.
A new thermostat with a working sensor removes a faulty reading as a cause, but it will not fix a dirty filter or a failing AC.
A smart thermostat costs more than a basic replacement, so buy one for its features, not to save on the replacement itself.
Content writer from Croatia. Dominic studies Information Science at the University of Sarajevo, which helps him research and organize his work.
