If you have a Tesla Powerwall and your utility offers time-of-use (TOU) rates, you're sitting on a goldmine of potential savings. But most Powerwall owners leave money on the table because they don't optimize for TOU properly.
This guide explains exactly how TOU optimization works, the strategies that save the most money, and why automation makes all the difference.
What Are Time-of-Use Rates?
Time-of-use rates charge different prices for electricity depending on when you use it. Most utilities have:
- Peak hours (typically 4-9 PM) - Highest prices, often 2-4x the off-peak rate
- Off-peak hours (typically overnight) - Lowest prices
- Mid-peak hours (mornings and early afternoons) - Moderate prices
Some utilities like ComEd (Illinois) and Octopus Energy (UK) offer even more dynamic pricing - hourly rates that change based on real-time wholesale electricity prices.
Why TOU Exists
Utilities charge more during peak hours because that's when demand is highest and electricity is most expensive to generate. They want to incentivize shifting consumption to off-peak times. Your Powerwall lets you do exactly that.
How Powerwall TOU Optimization Works
The basic strategy is simple: charge your battery when electricity is cheap, use it when electricity is expensive.
Without Solar Panels
If you don't have solar, your Powerwall can charge from the grid during cheap off-peak hours (usually overnight) and discharge during expensive peak hours. You're essentially buying low and "selling" high.
With Solar Panels
Solar adds another dimension. During the day, your panels generate free electricity. The question becomes: should you use that solar to charge your battery, power your home, or export to the grid? The answer depends on your current rate, export credits, and forecasted solar production.
The Two Powerwall Modes Explained
| Mode | Best For | Behavior |
|---|---|---|
| Self-Powered | High-rate periods | Maximizes solar self-consumption. Battery only charges from solar. Avoids grid imports. |
| Time-Based Control | Cheap-rate periods | Allows grid charging during off-peak. Uses your rate schedule to decide when to charge/discharge. |
The optimal strategy switches between these modes throughout the day based on your current electricity rate.
Manual vs. Automated Optimization
Manual Approach
You could optimize manually by:
- Checking your utility's rate schedule daily
- Switching Powerwall modes at rate change times
- Adjusting for weather (cloudy days = different strategy)
- Accounting for your usage patterns
This takes 5-10 minutes per day and requires constant attention. Miss a peak period, and you've lost money.
Automated Approach
Automation tools like BatteryProfit handle all of this 24/7:
- Sync your utility's rates automatically (including real-time pricing)
- Switch Powerwall modes at the optimal times
- Factor in weather and solar forecasts
- Predict your energy usage with machine learning
- Never miss a peak or off-peak window
The Math on Automation
If manual optimization saves you $50/month but takes 10 minutes/day, that's 5 hours/month of your time. Automation costs ~$1.67/month and runs 24/7 without any effort. The ROI is obvious.
Advanced Strategies
Reserve Management
Your backup reserve setting determines how much battery capacity is kept for outages. During TOU optimization, you might want to lower this during safe conditions (good weather, reliable grid) and raise it before storms.
Solar Forecasting
Knowing tomorrow's solar production helps you decide whether to charge from grid tonight. If it's going to be sunny, you might skip grid charging and let solar fill your battery for free.
Load Forecasting
Machine learning can predict your home's energy consumption based on historical patterns, weather, and day of week. This helps size your overnight charging correctly.
Automate Your TOU Optimization
BatteryProfit handles all of this automatically. Solar forecasting, load prediction, rate syncing, mode switching - 24/7.
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