The aim of this plug-in is to make the HomeKit environment aware of when a household equipped with power generation (typically a solar system), is exporting power. This will allow the construction of automations which can take advantage of the excess power (e.g. running heating or cooling systems, hot water systems, and clothes dryers).

This plug-in utilises the HomeBridge system, and is designed to interface with a Iammeter power meter. IAMMeter provide single and three phase power meters which are bi-directional (i.e. capable of measuring both forward / Grid and reverse/ export power). These devices are suited to monitoring power consumption and export for sites equipped with grid connected solar systems.

This project will initially focus on only the single phase meter.

This project provides an output via a virtual light bulb which is configured to come on at a set export level (onThreashold) and turn off when the output drops to a set level (offThreshold). To avoid rapid on/off cycling of devices, the on thread hold should exceed the off thread hold by the usage of any automated devices. A large polling interval is also recommended (default 120 seconds) to further avoid cycling.

This project has now achieved MVP for the single phase meter and is released for user evaluation. Feedback will be warmly welcomed.

To install this plug-in via the HomeBridge GUI, simply search for "IAMMeter" within the plug-in search and then install the package "homebridge-iammeter-accessory" from the list.

For Manual install, enter the below command into the system terminal

npm install homebridge-iammeter-accessory

edit your Homebridge's config.json to include the following in the accessories section:

"accessories": [
        {
            "accessory": "Meter",
            "name": "Meter",
            "ip": "192.168.1.177",
            "username": "admin",
            "password": "admin",
            "pollInterval": 120,
            "onThreashold": -1000,
            "offThreashold": 0
        }
]

I am currently toying with several ideas in this space. Similar implementations have used various parameters such as volume and brightness to act as a proxy for power which is currently unsupported in HomeKit. From a functional point of view, I expect the likely use case to be something like "when export power exceeds x, then turn on device Y". Thus I have implemented a simple virtual indicator (lamp) with a pre-defined "on" value as the most useful way to implement the functionality.

In many areas of the world exported solar energy is readily consumed by the grid and offers financial incentives to the exporter. However, some area's, such as my home state of South Australia, have now reached very high levels of solar generation and are producing excess available power. In these area's it is now more beneficial for both the owner and environment to utilise this excess power to avoid the use of fossil fuel based energy sources when the sun is not shining. This is the impetus for building this plug-in. An "export aware" smart home could intelligently utilise this power to:

• Pre-heat or cool the house
• Charge an electric vehicle
• Operate a clothes dryer
• Run an electric hot water heater
• Charge batteries and battery operated devices

Hopefully this plug-in will be useful to members of the Homebridge Community and will increase in uptake as the penetration of embedded solar generation increases.

This plug-in was developed from the following base example:

https://github.com/homebridge/homebridge-examples