How a Home Battery Works with Solar
A Tesla Powerwall 3 stores energy from your solar panels and the grid, then uses it to power your home when electricity is most expensive or during outages. It charges from solar during the day and from cheap off-peak grid energy overnight, discharging automatically during peak hours. Storm Watch pre-charges before severe weather.
Key facts
- ✓ Powerwall 3 stores 13.5 kWh of usable energy per unit.
- ✓ Built-in solar inverter supports up to 20 kW of panels.
- ✓ Storm Watch auto-charges before severe weather for back-up power.
- ✓ Octopus Intelligent Flux arbitrage works with or without solar.
- ✓ The Tesla app monitors energy flow and battery charge in real time.
- ✓ Installation is carried out through MCS-certified partners.
Last updated: 28 October 2026
The Energy Flow
Solar Generation
Panels generate electricity. Powerwall manages the flow.
Battery Storage
Excess solar stored for evening and cloudy periods.
Tariff Arbitrage
Charge off-peak, discharge peak on Octopus Flux.
Storm Watch
Auto-charges before storms, back-up during outages.
What Gets Installed
Solar Panels
Generate electricity from daylight. Optional but maximises benefit.
Powerwall 3 Unit
13.5 kWh battery with built-in inverter. Wall-mounted, IP67 rated.
Consumer Unit
Integrates with your existing electrical panel automatically.
Tesla App
Monitor energy flow, charge, and Storm Watch alerts in real time.
Octopus Intelligent Flux
A time-of-use tariff with cheaper off-peak and higher peak rates. The Powerwall charges when electricity is cheap and discharges when it is expensive, automatically trading the price difference.
This means you can reduce your electricity bill even without solar panels. Combined with solar, the benefits stack: solar energy during the day, cheap grid energy stored overnight for peak use.
Back-Up Power and Storm Watch
One of the most valuable features of the Tesla Powerwall 3 for Scottish homes is automatic back-up power during grid outages. Scotland experiences regular power cuts, particularly during winter storms and in rural areas. When the grid goes down, the Powerwall automatically switches to back-up mode, keeping your essential circuits running without interruption.
Tesla's Storm Watch feature is unique to Powerwall. When severe weather is forecast, the Powerwall automatically charges to full capacity from the grid or solar, ensuring maximum stored energy before the storm hits. Once the storm passes, it returns to normal operation. This happens without any user intervention.
The back-up system can be configured to power your whole home or just essential circuits like lighting, refrigeration, heating controls, and internet. Your installer will discuss the best configuration during the survey, based on your household needs and the capacity of your electrical system.
Monitoring and Control with the Tesla App
The Tesla app gives you real-time visibility into how your Powerwall and solar system are performing. You can see energy flow between solar, battery, grid, and home at any moment. The app shows how much energy your solar panels are generating, how much is stored in the battery, and how much your home is consuming.
You can choose between different operating modes. Self-Powered mode prioritises using stored solar energy before drawing from the grid. Time-Based Control mode optimises charging and discharging around time-of-use tariffs like Octopus Intelligent Flux. Back-up Reserve mode keeps a specified amount of energy in reserve for power cuts.
The app also sends notifications when Storm Watch activates, when installation is complete, and when software updates are available. Over-the-air software updates from Tesla keep your Powerwall running the latest firmware with new features and improvements, without needing a site visit.
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Reviewed by the Scottish Energy Efficiency team