Electric fans are on the rise again, after soaring more than 80% in a matter of hours on Friday after the stock market plunged on a strong market sell-off.

The Nasdaq composite index gained more than 1,000 points, or 2.6%, to 17,081.54 on Friday morning, the biggest weekly gain since Jan. 3.

That’s the largest gain since Oct. 30, 2008, according to FactSet.

The stock market is still relatively thin, with the S&P 500 at 1,831.50 and the Dow at 4,542.94.

That would leave the Dow as the biggest index in history with a total market cap of $6.6 trillion, according the FactSet website.

The market rally was sparked by news of Tesla Motors Inc.’s (TSLA.

O) announcement that it is buying SolarCity Corp.SCCY.

O, which has raised more than $50 billion in funding since 2014, for $2.6 billion in cash.

The stock rose $1.85, or 0.9%, to close at $39.50.

Tesla shares rose about 1% to $48.65 on Friday.

SolarCity shares rose nearly 8% to close around $40.00.

Tesla, the first electric carmaker to go public in 2015, is in talks to buy SolarCity’s battery technology company.

SolarCity, which says it can make batteries cheaper, is one of the most valued companies in the world, and investors have long expected a deal.