Redfin is continuing its West Coast expansion, with plans to announce today that its online real estate brokerage service will be available to consumers in Los Angeles, Orange County and San Diego.

Southern California is the biggest market to date for the Seattle startup, increasing the number of properties for sale on its site more than 300 percent.

Like in Seattle and San Francisco, those who buy a home through Redfin will receive a refund of two-thirds of the buyer's commission.

Redfin, which has raised about $9 million from Madrona Venture Group, Vulcan Ventures and others, has caught flack in the past for trying to disrupt the current real estate model.

It plans to expand into Boston, Chicago and Washington, D.C. later this year.