Try an Energy Meter in Home Assistant—Before You Buy One

Wondering how an energy meter would fit into your Home Assistant setup? Try it before you buy. With IAMMETER's online simulator, you can set up MQTT discovery, explore simulated WEM2067 readings, and experiment with dashboards and automations—without buying or wiring a meter. When you're ready for the real hardware, the same MQTT setup steps apply.

This hands-on guide uses the WEM2067 online simulator and Home Assistant's built-in MQTT integration. Home Assistant discovers the simulated meter and creates its sensor entities automatically. You won't need an IAMMETER HACS integration or individual sensor definitions in YAML.

1. Get your MQTT broker ready

You'll need an MQTT broker, such as Mosquitto or EMQX. An existing broker is fine: the key is to connect both Home Assistant and the simulator to the same broker.

We'll use the following examples throughout. Replace them with your own connection details:

mqtt.example.com is a placeholder. Your broker must be reachable from both Home Assistant and the simulator server. A broker address that works only on your home LAN will not work with the public online simulator. The broker does not have to run on the same machine as Home Assistant.

2. Connect Home Assistant to MQTT

1. In Home Assistant, go to Settings → Devices & services → Add integration, then search for MQTT.
2. Enter your broker's hostname, port, username, and password. In our example, the host is mqtt.example.com and the port is 1883.
3. Submit the settings to connect. The host field takes a hostname or IP address only—leave out http://, mqtt://, and any URL path.
4. MQTT discovery is enabled by default, with homeassistant as the discovery prefix. If you've changed it, make sure it matches the prefix used by the meter.

Already connected to the right broker? You're ready for the next step. There's no need to add another MQTT integration or change your existing connection.

3. Configure the simulator and enable discovery

Open Settings in the simulator below and enter:

The public simulator currently accepts upload intervals from 10 to 3600 seconds. We'll use 10 seconds here.

Click Save. The simulator connects to your broker, publishes the Home Assistant discovery configuration, and sends simulated readings at the chosen interval. Notice that the simulator's Address field combines the host and port, unlike Home Assistant's separate fields.

Keep the simulator page active while testing. By default, background uploads stop after five minutes without page activity. Your settings remain saved, but readings stop being sent.

4. Find your meter in Home Assistant

Return to Settings → Devices & services → MQTT and look for the meter in the device list. The WEM2067 simulator used here has the serial number ZAT3LQD9.

This example creates one WEM2067 device with 12 sensor entities: voltage, current, power, power factor, imported energy, and exported energy for each of its two channels.

Open the device and check the readings for channels A and B. Wait at least one upload interval and confirm that the values and update timestamps continue to change. In the default inverter-and-grid scenario, channel A represents solar generation and channel B represents grid import/export. Negative power on channel B means electricity is being exported to the grid.

Once the readings are updating, you can use the entities in dashboards and automations. You can also try adding the energy sensors to the Energy dashboard; eligibility depends on the device class, state class, and unit reported for each entity in Home Assistant.

5. Check messages and troubleshoot

With HA MQTT Discovery enabled, this simulator publishes readings to:

wem/imeter_zat3lqd9/tele/monitor

To check whether messages are arriving, subscribe to this topic using the MQTT integration's topic listener. Discovery messages use the homeassistant/ prefix. With discovery disabled, the WEM2067 uses device/ZAT3LQD9/realtime instead, so make sure you're listening to the topic for the selected mode.

For more detail, see the simulator MQTT/MQTTS guide, IAMMETER MQTT discovery guide, and Home Assistant MQTT documentation.

Ready for a physical meter? The MQTT discovery setup follows the same steps. Connect Home Assistant and the meter to the same broker, enter the MQTT details in the meter's Settings, enable HA MQTT Discovery, and check the discovered device and entities in Home Assistant. The meter needs firmware that supports MQTT discovery. It also has its own serial number, so review the entity references in your dashboards and automations when you switch. Follow the physical meter MQTT discovery walkthrough for the complete setup.

MQTT is one of several options. Explore the IAMMETER Home Assistant integration guide to compare the available methods.

6. About the WEM2067

The WEM2067 is IAMMETER's dual-channel energy meter for home monitoring. Its two channels can measure a single-phase solar inverter and the grid at the same time, or monitor the two legs of a split-phase grid supply.

In the simulator's default scenario, phase A carries inverter generation data and phase B carries grid import/export data. This differs from the wiring diagram, where CTa measures the grid and CTb measures the inverter. See Section 2.2: Use Solar and Grid Data in Home Assistant for the mapping.