Richard Schulze, the founder of Best Buy, offered to buy the electronics retailer on Monday in a deal that would value it as much as $8.8 billion.

A deal near that price would be biggest ever buyout of an American retailer, according to S.&P. Capital IQ data, topping the $8.4 billion buyout of Toys “R” Us in 2005.

Mr. Schulze, who resigned from the company’s board in June, said he would offer Best Buy shareholders $24 to $26 for each of their shares in the electronics company, according to a letter sent to the board that he made public.

The offer represents a premium of 36 percent on the low end of his offer and a premium of 47 percent on the high end from the company’s closing share price on Friday. In early morning trading on Monday, Best Buy shares were up 18.8 percent, to $20.96.

“There is no question that now is the moment of truth for Best Buy and that immediate and substantial changes are needed for the company to return to its market-leading ways,” Mr. Schulze said in a statement. “I am deeply concerned that further delay and indecision will cause additional loss of both value and talented leaders who are now uncertain of the company’s future.”

With a 20.1 percent stake in the company, the Best Buy founder is the company’s largest shareholder.

In his letter, Mr. Schulze said he had held discussions with several private equity firms interested in participating in the deal, as well as with former Best Buy senior executives, including Brad Anderson and Allen Lenzmeier.

“Bold and extensive changes are needed for Best Buy to return to market leadership,” Mr. Schulz wrote. “The company’s best chance for renewed success will be to implement these changes under a different ownership structure.”

The Best Buy founder said he planned to pay for the acquisition by contributing $1 billion of his own money, securing investments from private equity firms as well as debt financing.

In his letter, Mr. Schulz said that “Credit Suisse, who I have retained as my financial adviser, is highly confident that it can arrange the necessary debt financing.”

Best Buy has $2.2 billion in debt and $1.1 billion in cash on hand, according to Capital IQ data.

In addition to Credit Suisse, the law firm Shearman & Sterling is advising Mr. Schulze.