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Difference between the EMS Gateway and the KM200/MBLAN2

Bosch has internet gateways for selected EMS boilers and heatpumps. It’s a range of models like the KM50, KM100, KM200 and MBLAN 2. Depending on the brand there are small variations. Nefit just calls it ‘Internet module’. There is an external model for existing boilers and an internal module for heat pumps. With this gateway and an app on your phone you can see (partly) what your boiler is doing.

The BBQKees EMS Gateways also give insight into boiler parameters.

I often get questions about the difference between the EMS Gateway and the Bosch KM200 Internet gateway. In this article I’ll explain it in more detail.

How does the KM200 work

The KM200 (and the other Bosch internet gateways) connect to the CAN or EMS bus of the boiler or heatpump and your home network. The data it captures from the bus is then sent to the cloud.
You need to install an app on your phone to see the data. The app does this by connecting to the cloud and retrieving your boiler data from the cloud. So all your boiler data is stored in the cloud.
It provides a link between your boiler and an app via the cloud.

How does the EMS Gateway work

The EMS Gateways also connect to the EMS bus of your boiler or heatpump and your home network. The data it captures is then sent to your home automation like Home Assistant or Domoticz.
It depends on how you configured your home automation on how you can access the data. Likely via a web interface on your pc but probably also via an app.
The EMS Gateway provides a link between your boiler and your home automation solely via your home network. So you do not need an external cloud service. All boiler data is stored locally in your home automation system.

Amount of available datapoints

Existing owners of a KM200 are often surprised by the amount of datapoints/entities the EMS Gateway provides over the KM200. With the EMS Gateway you usually get 60 entities of just the boiler alone. With some boilers and heat pumps this may add up to much more (100+). For thermostats and mixer modules it depends on the specific model but there are always some interesting values coming out.

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E32 back soon

Currently the E32 is sold out. We are still waiting on a shipment of boards before we can assemble new products.

The E32 will probably be back in stock before the end of October.

You can fill in your email address on the product page to be notified the moment stock is added.

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Settings not saved in firmware 3.4.2 and 3.4.3

Firmware 3.4.2 and 3.4.3 have a small bug. If they are flashed on a new Gateway or other ESP32, settings are not stored. This means when you set up the device, after reboot it loses all settings.
If you update from a previous version via the web interface this problem does not occur.
Gateways with this issue shipped in the past few weeks can be updated via the web interface to version 3.5.0 and then it will work.

If you get an error 500/server error when you load the 3.5.0 firmware via the web interface, you need to use the USB connection inside the Gateway to flash firmware 3.5.0.

The steps to update are as follows:

First download the latest 3.5.0 firmware from

The file is a bin file called EMS-ESP-3_5_0b7-ESP32.bin .

Next connect to the ems-esp wifi network of your new Gateway and go to settings->upload.
Choose the file you just downloaded.

The Gateway will now update and after a minute you should refresh the page.
(Perhaps you need to reconnect to the ems-esp wifi network again.)

Then on the Settings page it will show the firmware version. It should now show 3.5.0.

If loading 3.5.0 fails with error 500/server error please use the USB flashing method with the new EMS-ESP flash tool to flash the Gateway. You have to open the device to access the USB connector.

For the E32 it advised to connect the 12V DC power supply while flashing via USB if available.

Firmware 3.5.0 is still a beta, but it is packed with new features. You can now set the language to Dutch, English, German or Swedish.

One remark: if you set a language, all MQTT entities are renamed as well so you have to reload everything into Home Assistant etc again.

Instead of 3.5.0 you can also load 3.4.1 via the web and then upload to 3.4.3 the same way to stay on stable.