Home Assistant Integration for IoTaWatt, Open WiFi Electricity Monitor

This project provides IoTaWatt support through a custom integration for Home Assistant. It creates entities for each input and output present in IoTaWatt.

IoTaWatt is an open-source, Wi-Fi connected electricity monitor that sits in or next to your switchboard (breaker panel). It measures up to 14 circuits using clip-on current transformers (CTs) and a voltage reference, and records power, energy, voltage, current, power factor and frequency locally on the device, with no cloud service required.

In IoTaWatt you configure:

• Inputs: the physical channels, one per CT or voltage reference, for example "Hot water", "Air conditioner" or "Mains phase A".
• Outputs: calculated values built from inputs, for example "Total consumption = Mains A + Mains B", "House minus solar" or "Everything not individually measured".

It reads data from the IoTaWatt over your local network and creates Home Assistant sensors for every input and output, so you can:

• use them in the Energy dashboard (each power input also gets a daily energy sensor in Wh),
• show live power use on dashboards,
• trigger automations, for example "notify me when the dryer finishes" or "turn the pool pump off when the house draws more than X kW",
• keep long-term statistics and history.

Power (W) and daily energy (Wh) sensors are enabled by default. Voltage, current, frequency, power factor, apparent power (VA) and reactive power (VAR, VARh) sensors are created but disabled; enable the ones you need in Settings → Devices & services → Entities.

An IoTaWatt integration has been part of Home Assistant core since 2021.9, but it doesn't give outputs a unique ID.

A unique ID is what lets Home Assistant remember an entity between restarts. Without one, an entity can't be managed from the UI: you can't rename it, change its entity ID or icon, assign it to an area, or tidy it up, and it's harder to keep it stable in the Energy dashboard and long-term statistics. Since outputs are usually the most useful IoTaWatt values (totals, net consumption, "rest of house"), this matters.

The core team removed the output unique IDs because they're built from the output's name, which they didn't consider unique or stable enough. As a result, output sensors in the core version can't be customised and end up scattered rather than grouped and managed alongside the inputs.

The original custom integration kept this feature, but it became dormant and gradually diverged from the updated core version. This repository backports the core version and keeps the unique IDs for outputs, and also includes a few bug fixes of its own (see the releases).

Note: because an output's unique ID is based on its name, renaming an output in the IoTaWatt creates a new entity in Home Assistant. The old entity becomes unavailable and can be deleted from Settings → Entities.

Manufacturing of the IoTaWatt has stopped, so new units are no longer available from the original maker. The project is open source: the firmware source code is available at github.com/boblemaire/IoTaWatt, so existing devices keep working and hobbyists can continue to build, maintain and develop it. This integration remains available for everyone with an IoTaWatt.

The integration isn't in the default HACS list, but it can be installed as a custom repository via HACS or copied manually.

HACS

1. In HACS, open the menu (⋮) → Custom repositories.
2. Add https://github.com/darek-margas/iotawatt_ha with category Integration.
3. Install IoTaWatt and restart Home Assistant.

Manual

1. Copy custom_components/iotawatt into your Home Assistant config/custom_components/ folder.
2. Restart Home Assistant.

Because it uses the same domain (iotawatt), this custom integration replaces the built-in one. Home Assistant will log a warning that a custom integration overrides a core one; that's expected.

Go to Settings → Devices & services → Add integration → IoTaWatt and enter the IoTaWatt's host name or IP address. If authentication is enabled on the device, you'll be asked for the username and password.

• If the IoTaWatt's address changes, use Reconfigure on the integration entry instead of removing and re-adding it.
• If the IoTaWatt's password changes, Home Assistant shows a notification asking you to re-enter the credentials.

Requires Home Assistant 2025.6 or newer.

Open the integration entry → Configure to turn on optional sensors. Both are off by default. These options need the ha-iotawattpy 0.3.0 library, which comes with Home Assistant 2026.10. On older Home Assistant versions the integration uses the library version already installed, and the options aren't available.

• Lifetime energy sensors: adds an energy sensor for every power input and output that counts from the start of the IoTaWatt's datalog and never resets (unlike the standard daily energy sensors, which restart at midnight). These are ideal for the Energy dashboard. They are shown in kWh.
• Reactive energy (VARh) as running total: makes VARh outputs report reactive energy accumulated since the start of the datalog, instead of the reactive energy of the last 30 seconds, so they can be used in long-term statistics. The unit changes from VARh to varh.

By default the integration polls the IoTaWatt every 30 seconds. The IoTaWatt logs data every 5 seconds, and the integration won't fetch more often than once every 5 seconds.

If you want faster updates, disable automatic polling (integration entry → ⋮ → System options → turn off Enable polling for changes) and call the homeassistant.update_entity action on a schedule, for example every 5 seconds, targeting a single IoTaWatt entity. One entity is enough because all sensors are refreshed together.