Budget WiFi smart water heater only for 9$ with Sonoff TH16

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A few months ago, I decided to make my water heater smart and be able to control it remotely via WiFi. The idea was to optimize power consumption specifically from the boiler. There are already many smart or wifi lighting switches on the market, as well as universal switches that are suitable for all appliances. After short research I opted for the Sonoff TH16 Wifi Key.

sonoff th16

My main search criteria were the WiFi switch itself to withstand high amperage, as the water heater would load it quite a bit. Of course, the low price was also important. At the time of purchase, the largest amperage offered by Sonoff's products was 16 amps, hence the name of the model - TH16. There are also models with lower amperage such as TH10 and some higher, but these were for more serious home automation - with dozens of outputs, large sizes, and complex power connections. It's a good idea to check the power of your boiler before purchasing a WiFi switch. When overloaded, the unit may melt, ignite and cause a fire.

смарт бойлер sonoff

When I bought Sonoff TH16 on 21.11.2018 the price of this switch was about 9$. The other reason I decided to choose this wifi switch is that it has the ability to attach additional humidity and temperature sensors. In the case of connecting it to the water heater, these two options were not relevant, but it is good to have them just in case. With these two features of Sonoff TH16 home automation capabilities are endless. Therefore, with this WiFi key, you can make smart any electrical appliance you can think of and control it through your phone.

An important thing to know when buying a Sonoff WiFi switch is that your electrical network or specifically your boiler has neutral wire (the so-called "negative"). Everyone should have this output on the water heater but still, check it in advance. Without a neutral wire, the switch cannot function, as it requires constant access to electricity to be connected to your WiFi network. Bellow is the wiring diagram:

sonoff схема за свързване

First of all, I would like to say that connecting is very easy, even for me who is not an electrical engineer. The wiring diagram is very clear and precise. However, if you do not have the confidence, it is better to consult a specialist. Be careful! When connecting the switch, always unplug your main power outlet!

Below you will see my final result. As the niche itself provided for my water heater key is too small, I had to improvise. Another problem was the short wires, which did not allow me to bring the WiFi switch at the right angle. So I had to leave the Sonoff switch almost horizontally and to disguise it a little I bought a box for another large electric switch, which fit exactly into the boiler niche. This is the end result:


Supports tracking device status
Supports remote turn on/off connected appliance
Supports presetting temperature and humidity to turn on/off
Supports 8 enabled countdown/single/repeat timing tasks
Support checking real-time temperature and humidity
Support setting smart scene to trigger on/off other smart devices
Works with Amazon Echo, Echo Dot, Amazon Tap
Works with Google Home, Google Home Mini, Google Nest
Works with IFTTT


Input voltage: 90~ 250V AC
Input current: Max 10A /15A
Max. Power: 2200W(10A) /3500W(15A)
Humidity: 5%-90%RH, Non-condensing
Operating Temperature: 0ºC-40ºC(32°F-104°F)
Wireless Standard: 802.11 b/g/n
Security Mechanism: WPA-PSK/WPA2-PSK
Enclosure Material: Fire-retardant ABS V0
Dimension: 114*51*32 (mm)
Supported temperature, humidity sensors: Si7021, AM2301, DS18B20, DHT11
Gang: 1
Certification: CE, RoHS, FCC (Download), Declaration of EU RoHS Conformity


The design of the WiFi switch is not looking very good and it is no accident. Especially this device is not intended for external mounting, ie. the idea is to have it mounted in an electrical panel or hidden in some kind of electrical box. That is why its appearance is not very suitable for installation as a water heater switch, which is visible to everyone in your home. However, there are options for making the installation of the switch visually welcoming.

WiFi бойлер sonoff


Sonoff is a brand of the Chinese company ITEAD, which have been on the market for many years and specialize precisely in the field of home automation appliances. I would say that the build materials of Sonoff TH16 are of good quality. There are plenty of videos on YouTube that load, even in some cases, overload the switch and it kept working within acceptable limits. However, for the price of the device, we cannot ask for the highest quality materials.


I have already mentioned that Sonoff TH16's capabilities for automating various devices are almost endless. You can connect this WiFi smart switch to any device (which has a power of fewer than 16 amps). Considering the ability to connect temperature and humidity sensors, the ideas of home automation are getting even more.

The App - Sonoff has their own phone app which you can download for Android and iOS. Unfortunately, the application doesn't support Bulgarian, but it's super intuitive and I don't think anyone would have a problem using it. Connecting to your home's WiFi network is also very easy. There are picture instructions in the box that will help you quickly turn on and start using Sonoff.

With the application, you can switch the boiler on and off, set specific days and times (for example, nightly rate) during which it can be switched on and off, create a schedule and calendar. In general, the possibilities are endless. This way you can optimize the amount of electricity consumed by your water heater.

смарт бойлер


Easy to connect and activate

Stable, effective and multi-functional mobile phone app

Manufactured from well-known company specialized in the home automation industry

Option for connecting temperature and humidity sensors


Not the best design - not suitable for external mount

Not suitable for appliances with high amp usage

Requires neutral wire


For me, the Sonoff WiFi switch is a great choice. It combines quality at a very good price and the ability to connect it to your boiler to optimize your costs by saving on your electricity bill. For me personally, electricity consumption dropped by 30-40%. Of course, everything is very subjective and individual, but in my opinion, after a few weeks of testing and optimization, absolutely everyone will be able to significantly reduce electricity consumption from the boiler.

The application for controlling the WiFi switch is very stable, unlike other devices of some brands. In almost a year and a half of use, I have never had problems connecting to a boiler from anywhere in the world. The connection to Sonoff's servers is apparently quite stable and their downtime is minimized.

And with the application itself, you can do whatever you want with the on/off settings of the water heater - switch on at certain times and days of the week or month, recurring events, such as switching on every Thursday or any other day of the week. Basically everything you can think of. This gives you great flexibility for optimization.

wifi ключ ревю

Overall, I personally do not see any flaws in the Sonoff TH16 switch, except for its design. But as I said here the price is more important. In the end for 9$ you can make any water heater or another electric appliance smart and control it remotely from anywhere in the world.



Editor review

1 review

Budget WiFi smart water heater only for 9$ with Sonoff TH16
Overall rating | Общ рейтинг 
Great budget option for making you water heater or any other home appliance, a smart device and control it over the WiFi. It will give you a lot of flexibility to customize and lower you electricity consumption.
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Amazing little WiFi switch
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So many features packed in this WiFi switch. You can literally automate everything in your home. Design could be a little bit better.
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