Tesla reported blowout earnings this week, but its biggest growth driver wasn’t cars or robots.Its energy business grew by over 50% year over year, earning Tesla over $7 billion in revenue so far in 2024.Elon Musk said on Tesla’s earnings call that the energy unit is “growing like wildfire.”

Tesla has a secret weapon, and it’s not Elon Musk’s robotaxi or the Optimus bot.

The company reported blowout earnings on the strength of its automotive sales on Wednesday — but its biggest growth area was Tesla’s burgeoning business selling batteries and solar panels, not electric cars.

Revenue for Tesla’s energy generation and storage business was nearly $2.4 billion in the third quarter of 2024, up 52% from the same period last year.

That’s a big jump compared to revenue from Tesla’s automotive sales, which rose by 2% over the same period.

The energy business’s revenue so far this year exceeds $7 billion, meaning that it now accounts for nearly 10% of Tesla’s total revenue.

The segment primarily includes Tesla’s sales of solar panels and its Megapack and Powerwall battery storage systems.

It typically garners less attention than flashy but less lucrative projects like Tesla’s robotaxi and Optimus humanoid robots. Still, it has fast become a vitally important source of income for the automaker.

The growth of Tesla’s energy business was noted by Musk in the company’s Q3 earnings call on Wednesday, with the Tesla CEO describing it as a “gigantic opportunity” for the automaker.

“The energy storage business is growing like wildfire, with strong demand for both Megapack and Powerwall,” Musk said.

The billionaire said that Tesla’s Megapack factory in Lathrop, California, had hit an important production milestone of 200 units per week. Tesla also told investors that the company had installed a record number of Powerwall systems for the second quarter in a row.

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Tesla is also building a Megapack factory in Shanghai, which is expected to begin mass production in the first quarter of 2025.

Megapack is a commercial battery system used by grid providers to store energy and help avoid power outages. This is especially important as more providers switch to renewable energy sources that can be more intermittent than fossil fuels.

Tesla says one Megapack can store over 3.9 MWh of energy, enough to power an average of 3,600 homes for one hour. The company sells them for around $5 million apiece.

The Powerwall, meanwhile, is a home battery that allows customers to store energy generated by solar panels and use it to power their homes. It costs around $16,000 before incentives, and Tesla offers it in a package with the company’s solar panels and “solar roof” product.