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Shelly Pro 3EM (Gen2)

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State: untested Generation: 2 Chip: ESP32 Flash: 16 MB

🧰 Before you start · ⚙️ Config · ⚡ Flash it · 👀 What to expect · ↩️ Way back

A classic ESP32 like the Plus Plug S: partition table at the ESP-IDF default 0x8000, bootloader at 0x1000, 80 MHz flash frequency. Unlike the other profiles it has 16 MB flash and a large emdata partition.

Fact Value
Profile Pro3EM
Flash 16 MB (bootloader header and partition table)
Official package 2.1.0 (stable channel since 2026-10-14; Bootloader, partition table and filesystem are the same as in 2.0.1)
Partition table 0x8000 (ESP-IDF default)
Bootloader address 0x1000
App slot size 0x200000

Before you start

Check first:

  • the device runs Shelly's own firmware, not ESPHome yet
  • you know its IP address (--ip), or this PC is on the device's own access point (default 192.168.33.1)
  • the device can reach this PC: same network, port 8000 (--port) not blocked
  • your ESPHome config uses the partition table below and is compiled
  • a UART adapter is at hand as your way back (Recovery over UART)

Also:

  • You have a full flash backup (the Pro 3EM may keep meter calibration data in flash, see Notes).

ESPHome config

Important

build refuses a config without Shelly's partition table. Copy partitions/Pro3EM-stock.csv from this repository next to your YAML and keep CONFIG_PARTITION_TABLE_OFFSET: "0x8000".

esp32:
  variant: ESP32
  board: esp32dev
  flash_size: 16MB                       # the bootloader header says 16 MB: with 4MB `build --esphome-factory` refuses
  partitions: Pro3EM-stock.csv           # copy from partitions/ in this repository
  framework:
    type: esp-idf
    sdkconfig_options:
      CONFIG_PARTITION_TABLE_OFFSET: "0x8000"
      CONFIG_ESPTOOLPY_FLASHFREQ_80M: "y"   # without it `build` refuses: the bootloader header says 80 MHz
    advanced:
      enable_ota_rollback: false

ota:
  - platform: esphome
    allow_partition_access: true

Flash it

  1. Install the requirements (once):
pip install -r requirements.txt
  1. Fetch the official package:
python ota.py fetch Pro3EM --insecure
  1. Build: put your app into it; the ZIP goes to out/:
python ota.py build Pro3EM app.ota.bin --esphome-factory app.factory.bin --esphome-yaml app.yaml
  1. Check the device first. Nothing is sent:
python ota.py send Pro3EM out/Pro3EM-app-<date>.zip --ip <device IP> --dry-run
  1. Flash it (the log goes to a file with --log-file):
python ota.py send Pro3EM out/Pro3EM-app-<date>.zip --ip <device IP> --log-file

app.ota.bin and app.factory.bin are the two files ESPHome compiles. --dry-run only checks the device and, for this package, reads the update target slot. Command reference: Commands.

What to expect

send shows these lines at the default log level, in this order:

# Log line Meaning
1 Update target slot: 0 ... The slot check of send. Anything else: run python ota.py restore Pro3EM first
2 Device: The bootloader will be replaced ... (raw log: Boot: cur ... min ... update? 1) The installer will write ESPHome's bootloader. WARNING: ESPHome's bootloader was NOT written (update? 0) means it will not: build again with a higher --boot-min-version (why)
3 The progress (Update: ... %, one line that updates in place) up to 100 %, then Done: update installed, the device confirmed it The device restarts into ESPHome

Notes for this device

Pins. Not known. The ESPHome device database has no page for the Pro 3EM (checked 2026-10-12). Its page for the original Shelly 3EM (Gen1) warns that the energy meter's calibration data must be saved before flashing ESPHome. Whether the Pro 3EM keeps such data in flash has not been checked here: take a full flash backup first.

emdata. The stock partition table has an extra data partition emdata (0x510000, 0xaec000 bytes, about 11 MB) after the second app slot. It is in Pro3EM-stock.csv so ESPHome builds against the real layout; the update package does not touch it.

Bootloader min_version. The official package carries Shelly OS loader 1.0.2. The profile sets boot_min_version: 1.0.9, the default of the newer profiles, because a unit that Shelly has already updated can report 1.0.3 and would then skip a package with 1.0.3. The loader of a real Pro 3EM has not been seen yet.

Pro Sensor Addon. Shelly's update API lists the Pro 3EM with the Pro Sensor Addon as a package of its own, Pro3EMProAddon, and the Pro3EM package names it in its compatible field. This profile covers only Pro3EM. send reads that field as one pattern, so a unit that reports the app Pro3EMProAddon would stop at the model check unless you add --force.

The slot. The Plus Plug S, the other Gen2 device, first received the app in slot 1 and needed restore once; send checks the target slot for you (why).

Please report the file written by --log-file, especially the lines Update target slot, Boot: cur ... update? and Will write to slot.

Way back

python ota.py restore Pro3EM sends the official firmware back while Shelly firmware still runs.

Warning

  • Wipes Wi-Fi and settings. ESPHome opens its own access point or joins the Wi-Fi from your config; if nothing comes up, power-cycle the device (help).
  • No way back over the network once ESPHome's bootloader runs: restore gets no answer, only UART brings Shelly OS back (Recovery over UART). Take a flash backup first.
  • Flashed it? Tell us, also when it worked: open a device report.

Bootloader and slots · Troubleshooting · Recovery over UART