Salas O’Brien Chairman and Chief Executive Darin Anderson knows how to inspire the 4,100 employees at his engineering firm.
“They are working on the coolest projects on the planet,” he told the Business Journal.
Anderson’s comment appears to be the case. The Irvine-based engineering firm works on 18,000 projects annually, everything from audio and control processing for the Infrasound system in Las Vegas’ famous MSG Sphere to structural engineering on California’s first all-electric life science campus, the Avia Labs facility in Millbrae, to upgrading surgery suites and the emergency department at UCI Health’s main hospital in Orange.
Salas O’Brien’s expertise includes pharmaceutical, food and beverage and defense facilities, as well as labs for higher education clients and state systems.
“There’s a lot of renovations to make their systems work faster, better, more efficiently, so that they can bring lower costs to clients or deliver better for the clients,” Anderson said.
This year, the Irvine-based firm is ranked No. 3 on the Business Journal’s annual list of the fastest-growing private companies in the large firm category. It reported 12-month revenue of $834 million for the period ended June 30, 2025 – up 71% from two years ago.
“What’s happening is that the need for our systems continue to grow year after year,” Anderson said.
He expects the firm will cross the billion-dollar mark in revenue next year.
Energy Crisis
Salas O’Brien was founded by Carl Salas and Dan O’Brien at the height of the 1970s energy crisis as one of the first firms providing energy auditing in the nation.
Anderson started his business career as an auditor at Price Waterhouse in 1991 and then worked at a couple of engineering and electrical companies before joining Salas O’Brien in 2006.
In the past 15 years, the company’s grown 12,000%, and was named to Inc. 5000’s fastest growing company in the U.S. 13 years in a row, an honor that’s been reached by only 20 companies in the U.S., Anderson said.
“People come to us every day because their previous service providers failed to communicate, didn’t coordinate, and let them down,” the company says on its website.
“That’s why we’ve resolved to be different. We communicate with the whole project team.”
In 2024, Blackstone, the world’s largest alternative asset manager (NYSE: BX), invested in 20% of Salas O’Brien.
“It is the platinum seal of approval to say you’ve been vetted by the, we’ll say, the world’s most stringent investing organization,” Anderson said.
“They invest in world-leading organizations, which many have now become our clients, because they have made the introductions for us, and those clients have seen the value of what we can do to help them grow the business.”
The Rollup Strategy
Salas O’Brien has completed over 20 mergers and acquisitions deals since the beginning of 2023, with two that recently closed at the end of August.
So far this year, Salas O’Brien has completed eight mergers and has four more that will close by the end of the year. Two of the upcoming companies are based in the Northeast and each employs about 200, Anderson said.
These acquisitions help expand Salas O’Brien’s capabilities and typically offer the firm access to new clients.
For example, when the 80-year-old, Nashville-based I.C. Thomasson Associates joined Salas O’Brien over a year ago, it helped the company win a job with a new teaching hospital in the Midwest.
“We simply don’t lose clients, and we’re there with clients that are growing naturally because of the demand for their services,” Anderson said.
Employees also stick around.
Anderson said he’s proud that the firm has retained 95% of mid-and senior leaders during the past 15 years.
Critical Real Estate
Salas O’Brien recently added American Campus Communities (ACC), which builds university residences and QTS, a data center developer, to its roster.
“We work with institutional type of customers where their real estate is critical to their ongoing success as an organization,” Anderson said. “These clients, from government clients to Kaiser Permanente, rely on us to design their systems so they work most effectively.”
Salas O’Brien is currently designing systems for eight to nine different billion-dollar hospitals. The firm also works with SpaceX, NASA and Microsoft.
Despite some weakening in the past year, Salas O’Brien has not slowed down thanks to what Anderson calls a balanced portfolio.
“Whether supporting hyperscale data centers, helping hospitals electrify their systems, or integrating technology and cybersecurity into facility operations, our teams are showing up where clients need us most,” Anderson said.
By working across multiple industries, from designing multibillion-dollar hospitals to Google data centers, Salas O’Brien is not dependent on a singular client or sector.
“Our largest client today is T-Mobile, and it represents less than 1% of our total revenue,” he explained. “So even though we work with them on a national basis and do a lot of work for them, if something were to happen to them, it’s not going to crush our firm.”
About 70% and more of the firm’s work is dedicated to modernizing and upgrading existing facilities according to sustainability or efficiency goals, so that it doesn’t have to rely on new construction projects.
Organic Growth, Mergers and Acquisitions
While Anderson acknowledged that the Irvine office experienced some softening in the local market —the firm reported that Orange County billings fell 10% compared to a year ago—the overall company appears to be outpacing the rest of the industry.
“The industry is growing in our space by probably 2% to 4% a year, but we are winning more than our market share, so we’re growing about 9% organically,” Anderson said.
This means the firm has been selling more services and projects to existing clients and is also finding new ones.
“Data centers have taken off,” Anderson said. “Healthcare has been very strong and steady.
We’re getting new technology to take care of our people and communities, and patients better, and so they want to integrate the new equipment and new methodologies.
“Then you look at space exploration, you look at defense facilities, all of these – there’s trillions and trillions of dollars of the existing infrastructure that we work in that needs to be replaced, to be upgraded.”
