Saving the sun for the night
The sun delivers more than enough energy… but only by day, and just when hardly anyone is home. Tesla Energy’s idea is simple: panels that capture it, a battery that stores it and a house that uses it whenever it needs to, even at midnight.
One house, one whole day
Illustrative simulation: 7 kW of panels and a house that uses about 28 kWh a day, close to the average US home (about 30, according to the EIA). ↗ Each Powerwall stores 13.5 kWh (Tesla’s figure). ↗ Real values depend on location, season and habits.
The sun and the house don’t agree
Panels produce the most at midday. The house, on the other hand, uses the most early in the morning and, above all, at night: lights, cooking, heating or air conditioning.
With no battery, the midday surplus goes to the grid and at night you have to buy it back. With a battery, the house keeps its own sunshine. Try “No battery” above and watch how much more comes from the grid.
Why the grid doesn’t go away
On a cloudy day the panels produce much less and the battery never fills up. That is why these homes stay connected to the grid: it is the backup for bad days. And if the grid goes down, the battery can keep the house running on its own.
Megapacks: the battery for a whole grid
A sunny city has the same problem as the house, only giant: at midday there is energy to spare, and in the evening, when people get home, demand shoots up just as the sun goes down. That peak is usually covered by power plants that switch on only for a while.
A Megapack is a battery the size of a shipping container. Add Megapacks and watch them flatten the evening peak.
An illustrative town of about 10,000 homes. Each Megapack 2 XL stores about 3.9 MWh and delivers up to ~1.9 MW, according to Tesla. ↗
On April 30: Powerwall and Powerpack are unveiled. ↗
Usable capacity of Powerwall 2 and Powerwall 3. ↗
Almost 300 Powerwalls in one container. ↗
How long South Australia’s big battery took (2017): 100 MW and 129 MWh, expanded in 2020 to 150 MW and 194 MWh. ↗
The new generation, unveiled in September 2025. Four make up a 20 MWh Megablock. ↗
A power grid that runs on sun and wind
In its “Master Plan, Part 3” (2023), Tesla estimated that a world on sustainable energy would need about 240 TWh of batteries. ↗ Here is where each piece stands:
- Homes with panels and PowerwallOperational
- Megapacks that stabilize power gridsOperational
- Virtual power plants: thousands of coordinated PowerwallsOperational
- Megapack 3 and Megablock, made in HoustonIn development
- A sustainable global grid with 240 TWh of batteriesConcept
Approximate status as of October 2026; things may have moved on. In July 2025, in California, more than 100,000 home batteries, many of them Powerwalls, together delivered about 535 MW to the grid for two hours. ↗ As of mid-2026, the Megapack 3 factory near Houston was still under construction. ↗