Control your home A/C with your iPhone for $100

This weekend, I replaced my home thermostats with two wifi thermostats made by 3M and sold at Home Depot (Model #3M-50). Now I can control my home’s heating and cooling from anywhere inside our home or when I’m out of the house, simply by firing up an iPhone app!

Setup was _almost_ as easy as it could have been. The one thing 3M could have done better was make clear that unit requires _wired_ power because of the wifi. Incidentally, getting power to the 3M unit wasn’t hard– they have a video on their site that explains it really well. You simply take one of the unused wires in the bundle of A/C control cables that run from your A/C’s “computer” to your thermostat and you connect it to the power terminals on both ends.

Setting up the first unit, without breaks, probably took an hour and fifteen minutes. The second unit was done in under 30 minutes (because I knew exactly what I was doing).

In general, the unit works really well. Connectivity was one of my concerns because I’ve seen wifi devices that frequently lose connection– but so far it’s worked just fine whether I’m in the house on the wireless LAN or out of the house on another LAN or on my cell phone’s 3G connection. There’s an almost negligible lag time (less than 1s?) from making a setting change on your iPhone to having it show up on the corresponding thermostat.

Only complaint, so far: the physical thermostat device could be more user friendly. The main complaint here is that they stuck an important button (the “mode” button) on the right _side_ of the thermostat. So 1) it’s not self-evident how to toggle the mode (from HEAT to COOL to OFF), I think most people (like me) will have to spend a moment figuring out where it is and 2) once you know where the button is, you still have to check around the side to make sure you’re pressing the right one.

But overall, this product looks like it’ll be a winner at our house. I’m hoping to see a reduction in our gas and electrical bills because this will make it easier to turn down/off the A/C or heating when we go out of the house. We’ll see! I’ll post more as we continue to use this thing.

My old Honeywell thermostat

The 3M-50 wifi thermostat that I bought at Home Depot for $100 each

Here's the 3M-50 Wifi thermostat installed

Here's the 3M-50 wifi thermostat close-up

And finally, the reason I did all this, the iPhone app I can use to control my A/C and heating– here it’s showing the current configuration for my upstairs and downstairs iPhone apps

5 thoughts on “Control your home A/C with your iPhone for $100”

  1. Looks pretty cool. Do you have to go through their portal for web and phone access, or can you access this locally? Are the ‘stats actually running little webservers? Have you tried looking at them from a browser?


    1. I don’t think you can control the thermostats directly, though I know they have a set of web services and one could probably figure out how to interact with them directly, but I don’t think their web server has an interface for the web services. That interface is in the iPhone app and on their Internet site.

  2. It’s a small world Rakesh. I ran across this post while trying to get my 3M-50 thermostat to work and realized you are the Snapstream guy. You probably do not remember, but I interviewed with you guys back in 2002. Anyway, the 3M-50 didn’t work for me. I have a some creative wireless uses that make me stick with WEP. Unfortunately, WEP is supported but just doesn’t work–it will never join the network. So I figure I would remove the encryption just to make sure the remote control works. After removing the encryption from my router, I still can’t get the thermostat to register with the “cloud”.

    Oh well. If it did work, then I agree that it’s a great product. Take care,


  3. It’s a small world that’s only getting smaller and smaller. 🙂

    Yes, I remember interviewing you at SnapStream! Bummer you couldn’t get it to work, I use it everyday to tweak the A/C settings in my house. It was a bit flaky when I first installed it but an update to the iPhone app about 3-4 weeks ago have fixed whatever problem was there before.

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