Shelly Pro 3EM: Saldierende Energiemessung (Net Metering) mit Home Assistant Auto-Discovery

shelly_pro3em_net_metering.js

/**
 * Shelly Pro 3EM - Net Metering (Saldierung) & Home Assistant Auto-Discovery
 * 
 * This script calculates the total active power across all 3 phases (A+B+C).
 * It simulates a "net metering" utility meter:
 * - If Total Power > 0: Increases "Import" counter
 * - If Total Power < 0: Increases "Export" counter
 * 
 * FEATURES:
 * - Precise integration (runs every 0.5s)
 * - Persists counters to KVS (flash memory) to survive reboots
 * - MQTT Auto-Discovery: Automatically creates sensors in Home Assistant
 * 
 * SETUP:
 * 1. Enable MQTT in Shelly Settings
 * 2. Add this script in the "Scripts" section
 * 3. Enable "Start on boot"
 */

let CONFIG = {
    updateInterval: 500,      // Calculation cycle in ms
    saveInterval: 300,        // Save to KVS every 300 cycles (~2.5 min)
    mqttPrefix: "homeassistant", // Standard HA discovery prefix
};

let SHELLY_ID = undefined;
let energyReturnedWs = 0.0;
let energyConsumedWs = 0.0;
let energyReturnedKWh = 0.0;
let energyConsumedKWh = 0.0;
let saveCounter = 0;
let lastPublishedConsumed = "";

// 1. Get Device ID and start
Shelly.call("Mqtt.GetConfig", "", function (res, err_code, err_msg, ud) {
    SHELLY_ID = res["topic_prefix"];
    if (!SHELLY_ID) {
        print("ERROR: MQTT not configured or no topic_prefix found!");
    } else {
        print("Shelly ID found: " + SHELLY_ID);
        LoadCounters();
        // Announce device to Home Assistant after a short delay
        Timer.set(2000, false, AnnounceHA);
    }
});

// 2. Home Assistant Auto-Discovery
function AnnounceHA() {
    let haTopic = CONFIG.mqttPrefix + "/sensor/shellypro3em-" + SHELLY_ID;
    let deviceData = {
        "ids": [SHELLY_ID],
        "name": "Shelly Pro 3EM",
        "mf": "Shelly",
        "mdl": "Pro 3EM",
        "sw": "Script-Saldierung"
    };

    // Sensor 1: Import (Grid Consumption)
    let payloadImport = JSON.stringify({
        "name": "Saldierend Import",
        "uniq_id": SHELLY_ID + "_sald_import",
        "stat_t": SHELLY_ID + "/energy_counter/consumed",
        "unit_of_meas": "kWh",
        "dev_cla": "energy",
        "stat_cla": "total_increasing",
        "dev": deviceData
    });
    MQTT.publish(haTopic + "-import/config", payloadImport, 0, true);

    // Sensor 2: Export (Return to Grid)
    let payloadExport = JSON.stringify({
        "name": "Saldierend Export",
        "uniq_id": SHELLY_ID + "_sald_export",
        "stat_t": SHELLY_ID + "/energy_counter/returned",
        "unit_of_meas": "kWh",
        "dev_cla": "energy",
        "stat_cla": "total_increasing",
        "dev": deviceData
    });
    MQTT.publish(haTopic + "-export/config", payloadExport, 0, true);
    
    print("Home Assistant Auto-Discovery sent.");
}

// 3. Load/Save Persistence (KVS)
function LoadCounters() {
    Shelly.call("KVS.Get", { "key": "EnergyConsumedKWh" }, function (res) {
        if (res && res.value) energyConsumedKWh = Number(res.value);
    });
    Shelly.call("KVS.Get", { "key": "EnergyReturnedKWh" }, function (res) {
        if (res && res.value) energyReturnedKWh = Number(res.value);
    });
}

function SaveCounters() {
    Shelly.call("KVS.Set", { "key": "EnergyConsumedKWh", "value": energyConsumedKWh });
    Shelly.call("KVS.Set", { "key": "EnergyReturnedKWh", "value": energyReturnedKWh });
    print("Counters saved to KVS.");
}

// 4. Main Calculation Loop
Timer.set(CONFIG.updateInterval, true, function () {
    if (!SHELLY_ID) return;

    let em = Shelly.getComponentStatus("em", 0);
    if (typeof em.total_act_power !== 'undefined') {
        let power = em.total_act_power;
        let energyStep = power * (CONFIG.updateInterval / 1000.0); // Energy in Watt-Seconds

        // Logic: Net Metering
        if (power >= 0) {
            energyConsumedWs += energyStep;
        } else {
            energyReturnedWs -= energyStep; // power is negative, make positive for counter
        }

        // Convert Ws to kWh (1 kWh = 3,600,000 Ws)
        // We use a small buffer (3600 Ws = 1 Wh) to reduce float errors
        if (energyConsumedWs >= 3600) {
            let chunk = Math.floor(energyConsumedWs / 3600);
            energyConsumedKWh += chunk / 1000.0;
            energyConsumedWs -= chunk * 3600;
        }
        if (energyReturnedWs >= 3600) {
            let chunk = Math.floor(energyReturnedWs / 3600);
            energyReturnedKWh += chunk / 1000.0;
            energyReturnedWs -= chunk * 3600;
        }
        
        // Publish to MQTT if value changed
        let valC = energyConsumedKWh.toFixed(3);
        let valR = energyReturnedKWh.toFixed(3);
        
        if (valC !== lastPublishedConsumed) {
            MQTT.publish(SHELLY_ID + "/energy_counter/consumed", valC, 0, false);
            MQTT.publish(SHELLY_ID + "/energy_counter/returned", valR, 0, false);
            lastPublishedConsumed = valC;
        }

        // Periodic Save
        saveCounter++;
        if (saveCounter >= CONFIG.saveInterval) {
            saveCounter = 0;
            SaveCounters();
        }
    }
});