pwforecast 1.0.1

A Python module to charge/discharge Powerwall based on solar forecast and peak/off peak tariffs.

PwForecast

A Python module to charge/discharge Powerwall based on solar forecast and peak/off-peak tariffs.

Utilises the excellent TeslaPy by Tim Dorssers.

PwForecast is primarily designed for those with dual rate tariffs. If there is interest in expanding this to provide more flexible control for those with more complex tariffs, please let me know.

Getting Started

PwForecast requires a Solcast API key and Site ID. You can sign up for a free Hobbyist account which allows up to two sites and 50 API calls per day.

TeslaPy has great documentation on getting started. It even works with two-factor authentication enabled.

Rather than wrap TeslaPy, PwForecast requires an instance of a Tesla class passed to it. This allows you to configure the object based on your credentials before passing to PwForecast.

When using PwForecast, Self Powered mode is recommended. Time Based Control could be used if you need to charge faster than 1.7kW per Powerwall, but results may be unpredictable.

Overview

PwForecast has two main methods, set_peak_mode and set_off_peak_mode. Both can be configured using a PwForecast instance.

Here is an example showing how to configure teslapy and PwForecast:

import teslapy
from pwforecast import PwForecast

tesla_email = '[e-mail]'
solcast_api_key = '1234-1234'
solcast_site_ids = {'Site_A': '1234-1234',
                    'Site_B': '1234-1234'}

with teslapy.Tesla(email=tesla_email) as tesla:

    pw_forecast = PwForecast(teslapy_session=tesla,
                             solcast_api_key=solcast_api_key,
                             solcast_site_ids=solcast_site_ids)

Setting Peak Mode

Use this method when your peak rate starts. You can configure what backup reserve the Powerwall can discharge down to by setting the min_reserve_peak_rate value.

pw_forecast.min_reserve_peak_rate = 10  # Default 20
pw_forecast.set_peak_mode()

PwForecast will try to ensure power flow behaves as expected. Please see Retry Logic for more info.

A summary report will then be printed:

-----------------------------------
Powerwall state of charge: 19.7%
Powerwall backup reserve: 100%
Powerwall capacity: 26.59kWh
Powerwall state of health: 95.0%
-----------------------------------

Setting Off-Peak Mode

Use this method when your off-peak rate starts. This requires a little more configuration.

• Configure what backup reserve the Powerwall can discharge down to by setting the 'min_reserve_off_peak_rate' attribute.
• Configure the maximum backup reserve allowed by setting the 'max_reserve' attribute.
• Configure the amount of energy you require during the peak-rate.

pw_forecast.min_reserve_off_peak_rate = 25  # Default 30
pw_forecast.max_reserve = 95  # Default 100
pw_forecast.required_energy_peak_rate = 20000  # Default 30000
pw_forecast.set_off_peak_mode()

PwForecast will try to ensure power flow behaves as expected. Please see Retry Logic for more info.

A summary report will then be printed:

-----------------------------------
Solar forecast tomorrow: 10.2kWh
Powerwall state of charge: 19.7%
Powerwall backup reserve: 100%
Powerwall capacity: 26.59kWh
Powerwall state of health: 95.0%
-----------------------------------

Retry Logic

When setting backup reserve, it is common to take two or three attempts before power flow changes to the expected figures. As the Tesla API is unofficial, it is difficult to determine why. Waiting longer does not seem to fix this issue, although waiting upwards of 45 minutes does sometimes result in power flow eventually changing correctly. Re-applying the setting does appear to fix this issue. Perhaps the unofficial Tesla API is missing a commit command. Please do let me know if you have any ideas.

Calling set_peak_mode and set_off_peak_mode will set the backup reserve, wait 20 seconds, and then check site power flow to confirm the setting has been applied. If an incorrect power flow is detected, the method will retry up to the reserve_retry limit. If the retry_limit is reached, an exception will be raised. PwForecast will then attempt to apply the setting up to the global_retry limit, eventually raising an exception.

Both reserve_retry and global_retry can be configured on the PwForecast instance. The reserve_retry has been split from the global_retry to try and avoid exhausting Solcast API calls.

Advanced Configuration

PwForecast has a few advanced configuration options. Please check the class docstring for more info.