Utilities to manage and monitor a Tesla Powerwall

Our home is built on a hill, which severely curtails solar production during the winter months. The sun drops below the hilltop shortly after noon, production in summer is 8X higher than in December/January.

By default, a Tesla Powerwall will charge itself using surplus solar production after first powering the house. In our case this led to poor results, as solar production in winter never charged the Powerwall and therefore we paid for substantial Peak rate power every day. Financially it is better for us to charge the Powerwall during the day and let it power the house as much as it can during Peak hours.

The utilities in this project help in managing and monitoring a Tesla Powerwall for situations like this.

cmd/powerwall

A command line utility to set the charge percentage. We run it from cron on a Linux system. During winter months, at 6am we set the charge percentage to 100% to make the powerwall capture as much of the solar production as it can. At 3pm (partial peak) we set it to hold its current charge, and allow any remaining solar production to power the house. At 4pm we set the powerwall charge percentage to a lower value, allowing it to start powering the house during Peak hours.

The goal is to charge the Powerwall up to close to 100% each day. One might consider that letting the Powerwall vary between 20% and 60% provides the same financial benefit as 60% to 100%, however in case of power outage having 60% power available is preferable.

This utility communicates with Tesla's cloud service to control the Powerwall, so it requires the same username and password as used by the Tesla app on a phone.

cmd/powerwall_prometheus

A daemon to poll the the amount of solar, battery, and house demand every few seconds and export them on /metrics for Prometheus to monitor. Because it polls so frequently, it queries the local Backup Gateway directly and does not rely on Tesla's cloud service.

cmd/solcast_uploader (OBSOLETE)

A utility intended to run from cron at the end of the day, extracting production information from Prometheus to upload to solcast.com.au. A future goal is to use day-ahead forecasts from Solcast to determine how much to allow the Powerwall to discharge. solcast.com.au has discontinued the PV Tuning feature.

How to get started

All of these utilities are written in Go. I use Go 1.15, though earlier or later versions of the toolchain may work. To build all of the utilities: go build ./...

The binaries can be copied to /usr/local/bin: sudo cp cmd/powerwall/powerwall cmd/powerwall_prometheus/powerwall_prometheus /usr/local/bin

cmd/powerwall is intended to run from cron. There is an example_crontab.txt file in that directory showing how we use it.

cmd/powerwall_prometheus is run as a daemon. There is a systemctl script in that directory showing how we use it.

License

All code in this project is licensed under a 3-clause BSD license, as detailed in the LICENSE file in the top level directory.