Energy Support

Time-Based Control User Guide

Time-Based Control maximizes savings by optimizing how your Powerwall provides power to your home. With Time-Based Control, your Powerwall will charge from and discharge to the grid at certain times to take advantage of changes to utility rates that occur throughout the day and season.

How Your System Will Work

When Time-Based Control mode is enabled, Powerwall uses a technique called energy arbitrage. Energy arbitrage allows Powerwall to store energy when energy prices are low and to sell that low-cost energy back to the grid when energy prices are higher. Powerwall optimizes your charging and discharging behavior for this arbitrage with an energy forecast tailored to your home.

Note: Grid charging and discharging are not available with all utilities. Refer to your Powerwall ‘Settings’ menu to show specific options available to your site.

What is Energy Forecasting and How Does It Work

Powerwall continuously runs an energy forecast, which means Powerwall learns and monitors the patterns of your seasonal energy use and solar production. When there is not enough sun available for your solar production and the forecast shows that you are likely to use energy at a high-cost time (peak period), your Powerwall prioritizes charging during a low-cost time (off-peak period) and discharging during a high-cost time (peak period). This may lead to instances where your Powerwall is idle, as it waits for an optimal opportunity to discharge, resulting in the use of solar or the grid to power your home. This method enables you to keep your energy costs down and to support the grid when energy imports are needed.

Solar Forecasting

Powerwall also uses a solar energy forecast produced using satellite weather data. This forecast is used to predict your solar energy production as the weather changes and also helps Powerwall make better decisions about when to charge and discharge while Time-Based Control mode is enabled. For example, if a forecast predicts significant cloudy weather tomorrow, your Powerwall may be programmed to charge earlier from the grid during a low-cost time period instead of normally charging from excess solar.

Note: Because this smart forecasting needs time to learn about your energy usage, Time-Based Control may not behave as you would expect for the first seven days following installation.

How Time-Based Control Looks in the Tesla App

When in Time-Based Control mode, you can refer to the visuals on the home screen of the Tesla app to better understand how your solar and Powerwall are operating throughout the day. The home screen of the Tesla app for Powerwall and solar displays a live view of power at your home, including solar, Powerwall, grid-use and home power consumption.

The following sequence of screenshots demonstrates a day for a typical Powerwall owner when using Time-Based Control mode. This example shows a home in the summer, where there is excess solar production to be stored in Powerwall for later exports to the grid during peak demand periods.

Note: The exact times and power numbers may differ for your home, but the same concepts still apply. 

 
8 AM Sunrise
The day starts in an off-peak period, when energy prices are low. Tesla Solar Inverter is now providing power to this home while Powerwall is charging from excess solar and storing energy for later use.
Time-Based Control at 8am
Time-Based Control at 8am
 
12 PM Noon
Powerwall has now fully charged, so excess solar is exporting to the grid.
Time-Based Control at 12pm
Time-Based Control at 12pm
 
3 PM Shoulder (Partial Peak)

This home's energy costs have partially increased during the shoulder period. 

The homeowner has scheduled their air conditioning to start cooling their home before peak. Powerwall is programmed through energy forecasts to discharge energy to avoid higher grid costs. Powerwall isn’t exporting any excess energy to the grid yet. 

If your home doesn’t have enough energy to cover all your home energy consumption, you may see Powerwall allow your home to use energy from the grid during the shoulder period.

Time-Based Control at 3pm
Time-Based Control at 3pm
 
5 PM  Peak

It's now peak period, where energy costs are the highest, so Powerwall is programmed to discharge to support this home's energy consumption. Any excess energy is exported to the grid to maximize economic value.

Time-Based Control at 5pm
Time-Based Control at 5pm
 
9 PM  Shoulder

Powerwall has now fully discharged down to the configured backup reserve after peak. It’s now programmed to allow some energy imported from the grid during this partial peak period, because this home’s consumption after the peak period is typically low. 

If your home typically consumes a lot of energy after the peak period, and your shoulder period has high rates, Powerwall may be programmed to reserve energy to use towards powering your home during this period, too. 

Time-Based Control at 9pm
Time-Based Control at 9pm
 
Midnight  Off-Peak

This home’s off-peak period starts at midnight. There’s a Tesla vehicle now charging based on set charging schedules to maximize the use of low-cost energy. Even if Powerwall had stored energy available, Powerwall would not be programmed to discharge, even to help charge the Tesla vehicle, during the off-peak period. 

While Powerwall is not currently charging from the grid, if there is low excess solar production forecast for tomorrow, then Powerwall programming may initiate charging from the grid during this off-peak period to prepare for the next peak period.