Sensi Wi-Fi Smart Programmable Thermostat 1F86U-42WF Review

General Information

If you’ve already checked out some Wi-Fi thermostat reviews, you will have noticed that they all say that you need a ‘C’ wire for them to work. Well, with the Sensi Wi-Fi Smart Programmable Thermostat 1F86U-42WF in many cases you do not actually need that ‘C’ wire. That in itself is a great selling point for many users, but the Sensi Wi-Fi Smart Programmable Thermostat 1F86U-42WF is a great deal more than that. It offers easy flexible programming suitable for whether there is someone home all day or a house where everyone is out during working hours. It will send you alerts if the temperature is too high or too low, or if the heating or cooling system fails. You can control your system from anywhere in the world, through a PC or via a smartphone or tablet using the free Android or iOS app.

If you have more than 1 thermostat, you can control them all via the same account.

The 1F86U-42WF has a temperature accuracy of +/- 1 degree, compared with other thermostats that offer a +/- 5 degree accuracy. This may not sound a great deal, but having you home 5 degrees warmer or cooler than you want it can have a huge effect on your energy costs.

If, for example, you are away on vacation and part of your heating or cooling system fails, the Sensi will send you alerts enabling you to take action immediately – much better than coming home to a nasty surprise.

Emerson, who make the Sensi, produce 2 versions of this thermostat, this one, the Pro-Install 1F86U-42WF and the DIY-Install UP500W. There is no difference physically between them, but the Pro-Install version costs about 10% less and has a 5 year warranty versus a 3 year warranty.


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  • Compatible with most North American heating and cooling systems, simply swap the old thermostat out for the Sensi
  • In many cases a ‘C’ wire is not needed
  • Works within a +/- 1 degree accuracy
  • All setup and operation can be carried through a smartphone or tablet with the free Android or iOS app
  • Retains programming in memory during power outages
  • Sends alerts when the temperature exceeds or falls below set limits or if the heating or cooling system fails.
  • Local weather information
  • Backlit control panel
  • Automatic updating
  • Low profile, the thermostat sits very flat to the wall, it is only ¾” deep.
  • 5 year limited warranty with professional installation – see here for details


  • Cannot be set up with a PC, it needs a smartphone or tablet. After setup, it can then be controlled with a PC
  • No PIN lockout to prevent unauthorized tampering with the settings. A plastic guard is available, but this is Ok for commercial applications but may be a little unsightly in a home.

Ease of Use        4.7/5

New -Emerson Sensi Wi-Fi Thermostat 1F86U-42WF for Smart Home

The Sensi does not have some of the complex learning functions that thermostats such as the Nest has, so in many ways this is much easier to both set up and use. All the settings can be carried out remotely from a tablet or smartphone and then, once done, you can almost forget about it. It even switches the time for daylight saving and back again, automatically. If a problem should occur with your system, the Sensi will automatically send you an alert.

Installation        4.7/5

In many cases, with conventional heating and cooling systems, there is no need to have a ‘C’ wire. If you do not have a ‘C’ wire already installed, this can make installation so much easier. Then it is simply a matter of removing the old thermostat, remembering to mark which wires come from which terminal, and wire in the new. The product comes complete with screws, wall plugs, and batteries.

Programming    4.5/5

The Sensi operates on a 7 day cycle, so once you have set one week, the system just repeats. All the set up can be done either through the push-buttons on the thermostat itself or, the easier option, through a smartphone or tablet. There is an option to have 4 heat and 2 cooling settings for each day. If you need to change your settings for whatever reasons, you can do so easily through your smartphone, tablet or PC.

Energy Saving   4.5/5

New -Emerson Sensi Wi-Fi Thermostat

Much of the savings in energy costs will depend on how you used your old thermostat against how you use you Sensi. A little time spent initially making sure that it is setup to suit your needs, rather than switch on and leave running, combined with the ability to maintain your set temperature accurately, will help reduce your overall energy costs. As this thermostat is Energy Aware Qualified, in many areas energy suppliers will offer discounts for having this fitted. Emerson claims that up to 30% energy savings can be achieved.


Bottom Line      4.6/5

The Sensi Wi-Fi Smart Programmable Thermostat 1F86U-42WF has many points to recommend it. If you do not already have a ‘C’ wire in your installation, and you have a standard heating and cooling system, the fact that in many cases you can just install the 1F86U-42WF without having to run additional wires or find a way to work around it, is a very big plus point.

The initial setup and programming are simple and straightforward as is the ease of use once it is up and running. The fact that it does not have all the learning abilities of other more expensive programmable thermostats will be a plus for many users.

Although it may lack the sleek designs of thermostats such as the Nest and the ecobee3, it does mean that it will fit comfortably into most home decors.

Overall the Sensi 1F86U-42WF is rated as one of the best programmable thermostats available, based on its value for money, long warranty, ease of installation and use. We hope you find our Sensi Wi-Fi Smart Programmable Thermostat 1F86U-42WF Review useful