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Nest Thermostat Won’t Charge: 7 Causes & Fixes (2023)

Nest Thermostat Not Charging

Picture this.

You, snug and cozy dozing off in your cold bedroom.

Hours pass… There’s sweat. All over. “Am I in the Sahara?”

Your worst nightmare has come true – your Nest thermostat has stopped charging.

Don’t give up on getting a good night’s sleep!


Read on to find out:

  • Why your Nest thermostat isn’t charging.
  • 7 easy ways to get your Nest thermostat charging.
  • How your home air system matters more than you think.
  • 2 options to boost your Nest thermostat’s charging power.
  • And so much more…

Why is my Nest thermostat not charging?

Your Nest thermostat is not charging because some parts are not working. They are damaged or not set correctly in their place. Its software can also be the culprit. Not enough power can cause issues as well. Also, the thermostat base may be disconnected. Or your home’s filter system needs cleaning.

Nest thermostat not charging – 7 causes & fixes

#1: The battery is broken

A battery is like butter (or peanut butter and jelly) to your Nest thermostat. Without it, it just won’t work!

But what if the battery has gone bad?

The Nest thermostat E and the Nest Learning thermostat have internal lithium-ion batteries. They collect power through a USB cable. All batteries get worn out over time. This is the case for all devices.

The internal battery allows the Nest to operate even in a blackout. It can last for one to two hours.

However, the Nest thermostat doesn’t have an internal battery.

How many birthdays has your battery celebrated?

If the answer is five, prepare to say goodbye. Especially if you used it as the main power source. When used only as a backup, it can have a longer lifespan.

But don’t throw it away just yet.

You’re gonna need that dusty old box.

Check the battery’s warranty. It’s 2 years for the Nest Learning and a year for the Nest E and the regular Nest thermostat. Also, Nest Pro provides an extended warranty. Only if you took their installation services.

Note: The warranty no longer works if you:

  • Mishandled the device.
  • Broke it due to repairing it yourself.
  • Changed any of the internal parts (except removable batteries).

Ticked off everything? Ask for help from a Nest Pro.

Maybe it’s time for a change.

Unlike the other ones, the Nest thermostat allows for backup batteries. These can be handy during a power outage. Or in this case, your device refusing to charge.

Take the thermostat out of its base. Remove the old batteries from its back. Put in two new 1.5V AAA alkaline batteries. Get high-quality ones from a reliable brand. Then, place the device back on the base. It should click when secured.

Read also: Nest Thermostat Low Battery: 7 Easy Ways To Fix It 

#2: The C-wire isn’t attached correctly

The bridge between the power and your device *might* have fallen.

And no, it’s not pins and needles. Nor wood and clay.

This bridge is called the C-wire. It keeps your thermostat running. Definitely helpful when your batteries drain quickly or need more power.

Note: A nest can be installed without one. Your device will tell you if it’s needed. C-wires just supplement the current power source.

It probably needs a closer look.

Turn off your thermostat. Unplug if it’s connected to a power source. Look if the C-wire is connected. If not, tightly put it back. Restart the device. The power should flow smoothly by then.

#3: The C-wire is broken.

“So, I did #2. And it still didn’t work! I’m so done!”

Wait! Maybe you want to look at your C-wire again. It might have seen better days. Or begging to take a break.

See any signs of wear and tear? These can be:

  • Fraying.
  • Discoloration.
  • Burned areas.

The technology gods want to send you a message: Replace it!

“But I’m no technician!”

Don’t fret! Contact a Nest Pro from your area. They can install a C-wire on your thermostat. Better be safe than take the risk.

“Well, I ain’t scared of getting my hands dirty!”

You can replace the C-wire by yourself. Turn off the power before doing so. Remove the old C-wire. If there’s none, the C-space should be available. Get a new C-wire. Tightly insert it into the C-space. Then, start your thermostat.

Note: The warranty no longer works if you replace the C-wire. Or any other internal parts of the device.

Still won’t charge? Now you should ask for help from a Nest Pro.

“Is there an alternative for a C-wire?”

You may want to buy a Nest Power Connector. It works similarly to a C-wire. You can safely install it yourself.

Here’s a video of how it’s done.

No wiring or drilling work is needed.

Before setting it up, make sure that:

  • Your circuit breaker is shut off.
  • Your Nest thermostat is compatible.

The Nest Power Connector works with 24VAC HVAC systems. Millivolt or high voltage systems won’t do. 

Keep your house’s main power off when installing.

You must update your Nest thermostat. It should be able to recognize the Power Connector. You can do this in Settings. The Nest E and the Nest thermostat 3rd Gen don’t require this step.

Find the control board in your HVAC. If there isn’t one, look for thermostat wires. Label the wiring. Connect the wires to their pairs. Close the HVAC cover. Turn on the power.

Reading recommendation: Nest Thermostat Cycling On and Off: 6 Reasons and Fixes

#4: Your grid doesn’t have sufficient voltage

So, your C-wire is in place. But the Nest is still mocking you.

Your device charges with the power from your main grid. This keeps your device functioning at all times.

Your grid’s power supply might not be enough.

Heck no, it doesn’t need a major overhaul. Nobody’s got the time (and money) for that. 

Flip your circuit breaker

Sometimes, technology just needs a kick. That’s why the on and off switch exists. Try turning off your circuit breaker and back on again.

If everything else works, and not your thermostat, then find another way to charge.

Use an external charging cable

The Nest Learning thermostat (1st Gen) needs a mini-USB cable. While a micro-USB cable for the Nest thermostat E. The Nest thermostat has no USB port.

You can detach the thermostat screen from the main grid. Attach the USB cable. Plug in a power source. Then, charge for 4-5 hours.

#5: The software doesn’t work properly

Reset Thermostat Software

You’ve reached this point. The wires, the grid, the batteries – they’re all fine! You’ve had your Nest thermostat for only three days.

Surely, it couldn’t be anything serious?

You use the Nest thermostat all day, every day. Just like us, our gadgets can get tired too (or we like to pretend they do). Maybe it just needs a good ‘ol nudge.

Take out the oldest (and most obvious) tricks in the book. Only when all else fails.

Restart your thermostat

First, turn off your thermostat. Wait for at least thirty seconds. Then, turn it back on. No information is lost in this step.

Reset your thermostat

If rebooting didn’t help, reset it. This puts your device back to its original settings.

Before doing this, take note of all your preferred settings. This makes it easier to set it up again. You can also go to Settings and select Equipment. Here, you can record your chosen heating types and temperature settings.

Press your thermostat ring. Go to Quick View Menu and select Settings. Turn the ring to Reset and press.

#6: The thermostat isn’t attached to the base

Because it’s all about that BASE, am I right? *cricket noise*

The base carries all the wires. It’s also directly connected to your HVAC system. This ensures constant charging and flow of power.

Does your Nest thermostat look like it’s about to fall off? That could be why it isn’t charging.

“My Nest was about to scream ‘Geronimo!’”

Secure the Nest thermometer in place to its base. Then, the power should flow through.

#7: Your air filters are clogged

Your Nest Thermometer is one busy chap. It keeps cool or warm air moving all over your home. This means your air vents are working hard too.

Each air vent has a filter. This sifts dust and molds from the air. But all these dirty particles can pile up. It also causes hot air to build up.

Your Nest Thermometer has to work twice as hard. This triggers an automatic shut-off. Now, how will you charge it, then?

Don’t wait for spring to come!

Clean your air vents. Replace the old filters with new ones.

You’ll save electricity AND hospital costs. While also extending the life of your thermostat.

Changing filters is a job you can do yourself. It won’t affect your device’s warranty.

But when in doubt, contact a professional. A NestPro can also do this for you.

Bonus: FAQs

So. your Nest thermostat is going oh-so-well.

You don’t want those snags to get you. Or go through them again.

Then, you’ll surely want to remember these.

How much power does a Nest thermostat need?

The internal batteries need higher than 3.6V when charging. For software updates, there should be 3.7V. For activating the display, 3.6V is enough.

The Nest thermostat follows the Voc, Vin, and lin values. This measures the power sent to your thermostat. The values depend on whether you use a C-wire.

If you don’t use a C-wire:

  • Voc: 29 to 42V.
  • Vin: 29 to 42V (when system isn’t running) / 6 to 7V (when system is running).
  • lin: 20 to 40 mA.

If you use a C-wire:

  • Voc: 29 to 42V.
  • Vin: 29 to 42V.
  • lin: 100 or 200 mA.

Keep these values constant. So your Nest thermostat will run smoothly.

You may also wonder: Will Nest thermostat work without power?

How do I know if my Nest thermostat is charging?

Your Nest thermostat is charging if there’s a blinking red light at the top. It also blinks when the battery is low. The light stays still when charging is complete.

How do I save my Nest thermostat’s battery life?

Going on a family holiday for weeks? A month-long business trip? Or a three-day visit at Grandma’s?

When you’re out, you can conserve the device’s energy.

There are two modes:

  • Off Mode.
  • Eco Temperatures.

Let’s say you’ll be shopping for a few hours. Set your Nest thermostat to Eco Temperatures. This can be done manually or automatically.

On your Nest or Home app, select Away. With this, your thermostat will detect that nobody’s home. And it automatically sets to Eco Temperatures.

Maybe you don’t mind turning down the heating… just for a while.

Open your Home app, select thermostat, then Settings. Choose Preset and tap Eco. This manually sets it to Eco Temperatures.

Off Mode is for longer times away from home. This doesn’t shut down the system completely. But it keeps your house in safe temperatures. It also stays online. You can control it wherever with the Nest or Home app.

You don’t want to return to a giant freezer or an overheated sauna.

To set Off Mode for the Nest thermostat, Hold the touch bar. Turn Off will show on the screen. Slide the touch bar to Turn Off. Then, press the touch bar.

To set Off Mode for the Nest Learning and the Nest thermostat E, tap the screen for the Quick View menu. Twist the ring to thermostat, then press. Twist to Off, then press.

Maximize these modes as much as you can. And get the trouble of repairs and replacements off your hands.

Can I get a replacement for free?

The warranty states that Google can give a replacement. But only when they find a confirmed flaw in manufacturing.

In 2020, they had to replace some Nest thermostats. These showed a ‘w5’ error in their display. The devices also didn’t connect to Wi-Fi.

What if it didn’t charge right after I bought it?

You can contact support and file a warranty claim. Then, you’ll return the product. Google will cover shipping costs and examine the issue.

If the warranty covers the issue, you’ll get a refund. Or better, a replacement.

But if not, you’ll have to pay for shipping.