Google Nest Learning Thermostat (4th gen) + Nest Temperature Sensor (2nd gen) - Obsidian

First ImpressionsI live in an older apartment where wiring is… let’s just say vintage. No powered “C-wire” or whatever the pros call it, so I half-expected this Nest to laugh in my face. Instead, it installed easily and worked like a charm—no extra adapters, no electrician visit, just smooth sailing.PerformanceLearns fast. Within a few days, it figured out my routine and started adjusting temps automatically. Now it feels like the thermostat knows me better than my landlord.Eco mode. The adaptive energy-saving feature keeps the bills from looking like a ransom note, which is a big win.Temperature sensor. Handy little add-on that makes sure the whole place is comfortable, not just the hallway where the thermostat lives.IntegrationWorks seamlessly with Alexa and Google Home—I can bark orders at it from the couch without lifting a finger.The Google Home app makes remote adjustments stupid-easy. Forgot to turn down the heat before leaving? Fixed in two taps.DesignThe Polished Obsidian finish looks slick. It’s the one piece of tech in my apartment that actually makes the place feel modern instead of “grandma-chic.”ProsWorks perfectly even without a powered line (C-wire).Learns habits quickly and adjusts intelligently.Saves energy without me thinking about it.Easy integration with Alexa and Google Home.Sleek design that looks expensive.ConsIf you’re not tech-friendly, setup might take a minute (but once it’s in, it’s golden).Bottom LineThis thing is smart, stylish, and makes my old apartment feel brand new. It saves energy, keeps me comfortable, and didn’t require rewiring the building.

The Google Nest Learning Thermostat (4th Gen) is everything you’d want in a modern smart thermostat—intuitive, efficient, and elegant. Installation is straightforward, even for those with limited DIY experience, and once it’s up, it blends seamlessly into any décor with its sleek, minimal design.What sets this model apart is the learning capability. Within a week, it started automatically adjusting to my schedule—lowering temps at night, warming the house before I woke up, and even dialing back when it sensed I was away. The energy-saving features are excellent, with detailed reports that show exactly how much you’re conserving.The interface is simple yet powerful. You can control it from the wall unit, the app, or by voice with Google Assistant or Alexa. The responsiveness is fast, and the temperature adjustments feel precise, unlike some smart thermostats that lag.For anyone looking to cut energy costs, improve comfort, and enjoy the convenience of automation, the Nest Learning Thermostat is a top-tier choice. It doesn’t just manage your climate—it actually learns your lifestyle and adapts to it.

This is my second Nest thermostat and I’ve recommended them to everyone!! It has my power bill down to $125 a month for a 1300 sq ft house in Alabama. I love that I don’t have to remember to adjust it before leaving the house. It’s also really pretty.

When one of our 3rd Gen Nest Thermostats stopped working, I decided to replace it with a 4th Generation Nest unit. Oddly, the mounting hardware for the 4th Generation is completely different from the 3rd Generation, which is annoying. The wiring backplate is incompatible, as the 4th Generation has a different electrical connector to the thermostat. One nice thing about the new backplate is that there is a light built into the bubble level which signals voltage on the Rh or Rc wires from the HVAC unit, implying you won't need a dedicated C wire for power. Unfortunately, this is many times not the case for the 4th Generation, lit bubble level or not.When I properly mounted and connected the 4th Generation thermostat, the setup app on my phone reported that there was "no power" on the R wire, even though the bubble level was lit, and I could measure the voltage on a multimeter. There was no way to get around the error message in the app. A call to Google support was completely useless. The support person clearly didn't know why the setup app falsely reported "no power", or whether or not the 4th Generation thermostat required higher voltage on the R wires than the 3rd Generation thermostat for operation without a C wire.An internet search revealed numerous people posting on Reddit and other web sites of the same issue I was having. How could Google support not be aware of this? Depending on your view, the difference between the R wire voltage requirements for the 4th Generation from the 3rd Generation thermostats is either an undocumented design change, or a design flaw. Personally, I consider it a significant design flaw, especially that it is not documented in the setup instructions, and there is no warning of this anywhere in Google's documentation.After spending about two hours removing the 3rd Generation mount, installing the 4th Generation mount, waiting for the callback from Google, and figuring out the root cause myself, I unmounted the 4th Generation Nest, packaged it back up, and returned it. I ordered a new 3rd Generation Nest from Amazon, and it works flawlessly with the HVAC unit.One attraction of the 4th Generation Nest is that the "maintenance band", the temperature variance range at which the AC compressor cycles on and off, is manually programmable, while on the 3rd Generation Nest it is not. There have been complaints that the 3rd Generation Nest's maintenance band is only two degrees F wide, which in some climates and homes cycles the compressor too often, and is blamed for excess wear and premature failure on the compressor. (AC units and heat pumps both use compressors.) So if you have a C wire in your compressor-based system, I recommend trying to use a 4th Generation Nest. Another trick which works with both generations is to use a remote sensor in a different part of the room or another room where the ambient temperature doesn't vary as quickly, to reduce compressor cycling. I use this trick for our 3rd Generation Units, and it also works for 4th Generation thermostats. Note that using a remote sensor this way may require some experimentation to get the desired result, while the feature to manually adjust the maintenance band makes it quicker and simpler.I really like the Google Nest thermostats when they're working the way they're supposed to, but the lack of backward functional capability from the 3rd Generation model to 4th Generation model is inexcusable, since there's no warning about it. And Google support is ineffective in helping less technical buyers. The least Google could do is document the issue properly on their web site.

I was up in the air about spending the extra money upgrading to this gen but very happy I did. I have more control over the thermostat then previously. Just in the past couple weeks during the hottest part of summer this year I have saved more energy then the 2 previous summer months while not losing comfort. Now to be fair we live in the lower level of home (split level house) but that extra sensor it comes with really helps alot. Also this one really does learn better the the gen 3 and that has helped as well. Now it uses the Google Home app, not the Nest app.....took me a day to figure that out because I'm too impatient to read.