WALTER — Solar Router for ESPHome

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(WALTER Always Loves Tiny Export Rates)

WALTER is a fork of hacf-fr/Solar-Router-for-ESPHome adding native support for the Shelly EM3 Pro / Pro 3EM three-phase meter, aimed at diverting photovoltaic surplus to a hot-water boiler.

WALTER does exactly what he says: it redirects the photovoltaic surplus to a boiler and keeps grid injection as low as possible.

Why the 3-phase sum?

On a three-phase contract the meter adds the three phases and bills only the net value. When one phase produces more (photovoltaic) than the other two consume, that's the right time to heat water.

Based on smart-meter readings, WALTER drives the boiler element as close as possible to that value. See docs/strategy.md for the full reasoning.

Hardware

Part	Model
MCU	ESP32 (esp32dev, esp-idf framework)
Regulator	RobotDyn AC dimmer 40 A "with current sensor" (heatsink NTC + CT, always-on fan)
Meter	Shelly EM3 Pro / Pro 3EM (HTTP RPC, polled locally — no HA needed)
Load	Pure resistive load up to 3000 W (water boiler)
Safety	boiler thermostat + local dimmer safety (heatsink thermal cutout, current-sensor health alarms)

• Wiring: docs/en/wiring_rbd40.md
• Safety procedure: docs/en/bench_test.md

Software

• Firmware: ESPHome. esp32-walter-solar-heater.yaml + the new package solar_router/power_meter_shelly_em3.yaml (3-phase meter poller).
• Home Assistant: helper templates & automations in homeassistant/ (tank-temp safety, peak/off-peak mode, dashboard).

ESPHome config (quick glance)

packages:
  solar_router:
    url: https://github.com/merryspankersltd/WALTER/
    ref: main
    refresh: 1d
    files:
      - path: solar_router/common.yaml
      - path: solar_router/power_meter_shelly_em3.yaml
        vars:
          power_meter_ip_address: "192.168.1.42"
      - path: solar_router/regulator_triac.yaml
        vars:
          regulator_gate_pin: GPIO17
          regulator_zero_crossing_pin: GPIO23
      - path: solar_router/engine_1dimmer.yaml
        vars:
          green_led_pin: GPIO18
          yellow_led_pin: GPIO19
      - path: solar_router/dimmer_safety.yaml
        vars:
          dimmer_temp_pin: GPIO34
          dimmer_current_pin: GPIO35
          red_led_pin: GPIO21

Credits & license

Built on hacf-fr/Solar-Router-for-ESPHome (GPL-3.0). See LICENSE. Read the upstream disclaimer before doing anything with 230 V.