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How to Turn Off Power to a Thermostat? – Only 4 Steps

Written by Edwin Jones / Fact checked by Andrew Wright

how to turn off power to a thermostat

Whether you’ve been meaning to do HVAC repairs or want to replace your property’s thermostat, you should know how to turn off power to a thermostat. This article lays out all the ways you can do this, particularly highlighting the ideal one.

Most modern residential thermostats have a single circuit breaker that serves all HVAC-related appliances, including the thermostat. I’ll start with that in my step-by-step guide as follows then proceed to other possible setups and scenarios.

Step-By-Step to Turn Off Power to a Thermostat


Let’s assume that you’re trying to turn off the AC thermostat because of maintenance. You can always just shut down the main breaker if you prefer an easy, straightforward way to cut power.

However, that means losing access to all your appliances. What if the job takes a longer time than usual? It’s not really practical, right?

This is why it’s best to adopt a more focused, narrowed-down approach as much as possible if you want to shut off power to a thermostat. In most cases, this means shutting down only the breaker serving the HVAC system.

Step 1: Locate the main panel or subpanel where your HVAC circuit breaker is found.

Usually, the HVAC circuit/s is in the main panel. If you’re not yet aware of its location, look for a rectangular box similar to the picture I shared above. You likely only need to open its cover without unscrewing anything.

Once you open it, you’ll see the rows of breakers arranged vertically or horizontally across the panel. Use a flashlight if there’s limited lighting because it’s important to pinpoint the exact breaker you need to turn off the heater thermostat or other type you’ve been meaning to service or replace.

Step 2: Confirm the number of circuit breakers serving your HVAC system.

If it’s just one and labeled to indicate that, yes, it’s the one connected to the HVAC circuit, then you can proceed to the next step. If there are multiple breakers involved in maintaining your HVAC’s whole circuit, then you’ll need to look for each one.

Numerous homeowners have asked me, ” Why, once they turn off the HVAC breaker, is the thermostat still on?” It turns out, they missed one or two other breakers still connected to it, like the ones serving the AC and furnace, for example.

Take note of every HVAC-related breaker, in short.

Step 3: Turn Off the Breakers.

Have you taken note of all the breakers serving the HVAC system? Good! Now, you only need to turn the breaker off.

All breakers’ switches are in the ‘ON’ position. It’s as simple as turning that switch to the opposite ‘OFF’ position to kill the power being supplied to the thermostat.

Incidentally, if you happen to discover that the thermostat has no power, you need to check if the breaker’s actually in the ‘OFF’ position. You never know when an electrician may make the mistake of turning it back on, after all.

Step 4: What if there are no labels on the breakers?

I understand that some properties were serviced by nonchalant electricians who don’t go the extra mile and label each breaker they install. If you find yourself cursed with such ill luck, then you have no other option but to apply a brute force method (i.e. turn each breaker off one by one.)

You need to figure out which breaker turns off the thermostat and any other circuit that may be connected to it.

Assuming there’s nothing marked, you have to turn off each breaker on your panel and see which appliance shuts off, until the thermostat itself shuts off – and most likely your furnace, AC, or heating system along with it.

Other Ways to Shut Off Power Based on Thermostat Type and Setup


The steps on how to turn off power to change the thermostat I highlighted above are what’s standard in most homes. But what if you’re using a wireless, WiFi thermostat or it’s one that’s connected to its own transformer?

1. How to Turn Off a Thermostat or HVAC Transformer?

This is just as common in most households. What’s good is that it’s not hard to cut the power in these setups.

You’ll only need to turn off the thermostat power switch to shut it down. If it’s connected to an AC or furnace transformer, that means you need to switch either one of those appliances to turn off the thermostat’s power.

Of course, this also means knowing which transformer to shut off, assuming there’s more than one.

2. How to Turn Off a Wireless or Smart Thermostat?

Do you mean you just want to disable the thermostat’s heating and cooling feature? If you want, for example, to turn off a thermostat Honeywell, you can often do so through the different Modes that the thermostat has available.

Usually, there’s a Cool, Heat, and Auto mode. The Off option is normally included there. This rings true for more advanced thermostats like the ones manufactured by Nest. Here’s a demo of how you can turn off their thermostat if it so happens that it’s the one found in your home:

Take note that some smart thermostats have batteries that may kick off once you shut down the power to the said appliances. This is why it’s best to know how to turn them off if you mean doing more major maintenance jobs and electrical work.


Hopefully, with the methods on how to turn off power to a thermostat I’ve laid out above, you won’t have to deal with head-scratching issues that usually come when you need to repair or replace these appliances. I also get that leaving your thermostat on all day only contributes to higher power bills.

Found this guide helpful? Do consider sharing it with other people who need help with their thermostats!

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