Arthur Rosenfeld, an experimental physicist who set aside his decades-long study of subatomic particles to help design energy-efficiency standards and technologies, reducing greenhouse-gas emissions and saving everyday Americans billions of dollars each year, died Jan. 27 at his home in Berkeley, California. He was 90.

The cause was complications from pneumonia, said a daughter, Anne Hansen.

Rosenfeld was “fueled by a passion to wring the most out of every kilowatt,” the Los Angeles Times reported in 2010. As a researcher at the University of California at Berkeley, he helped his adopted home state establish some of the country’s first, and most stringent, energy-efficiency standards.

For three decades, however, his research was limited to the study and discovery of subatomic particles, for which he used a special device known as a hydrogen bubble chamber.

It was only during the oil crisis of the mid-1970s that Rosenfeld turned to the field of energy efficiency, viewing it as a way for the United States to avoid future oil-embargo threats from the Organization of the Petroleum Exporting Countries.

While preparing to go home one Friday night in November 1973, dreading the seemingly inevitable half-hour wait at the gas pump, he turned off his office lights — a habit he developed as a child during the Depression — and began calculating the energy savings that his office would achieve if everyone else did the same.

Hunting for light switches on his 20-office floor, searching behind filing cabinets and book cases, he decided his laboratory “should do something about conservation,” as he later put it.

Rosenfeld began leading research efforts to calculate the savings of relatively simple acts such as turning off the lights — 100 gallons of natural gas saved per weekend at his office alone, he calculated — and getting rid of inefficient refrigerators and home appliances.

At a meeting with California Gov. Jerry Brown a few years later, Rosenfeld explained that if the state prohibited the most inefficient refrigerators, it could avoid building a controversial power plant known as Sundesert. Energy conservation, as Rosenfeld saw it, was easier, cheaper and altogether smarter than building new power plants.

Brown agreed, and in 1977, drawing from Rosenfeld’s research, he enacted what are considered to be the country’s first efficiency requirements for appliances. The standards, set initially only for refrigerators and freezers, were followed one year later by an energy-efficient building code that aimed to reduce residential energy usage by 80 percent.

Federal regulations established similar standards for home appliances in 1987.

At the same time, Rosenfeld and a team of researchers at Berkeley’s Center for Building Science developed several quietly revolutionary technologies: electronic ballasts that helped popularize the compact fluorescent lamp, an energy-efficient lightbulb; a coating for window glass that allows homes to trap heat in the winter and keep it out in the summer; computer programs that analyze buildings’ energy usage; and, most recently, a reflective roof design that aids with cooling.

In an autobiographical 1999 paper, Rosenfeld estimated that products developed at the center resulted in consumer saving of $30 billion each year. “In terms of pollution control,” he wrote, “this is the equivalent to displacing approximately 100 million cars.”

The efficiency standards that resulted from his research had a similarly striking effect. In what efficiency advocates and some scientists hail as “the Rosenfeld effect,” per capita energy usage in California has hardly grown since the mid-1970s — despite a seemingly endless proliferation of household gadgets, appliances and electricity-hogging televisions.

In the United States as a whole, per capita energy usage has more than doubled.

Rosenfeld faced early criticism from utility companies such as Pacific Gas & Electric, which suggested to Rosenfeld’s laboratory boss that the onetime nuclear physicist was unqualified to study energy-efficiency and ought to be fired. He was also sometimes blasted by appliance manufacturers and consumers, who were wary of products’ becoming more expensive.

“The first time we put standards on a product, we tend to get objections that this will be the ruin of civilization as we know it,” he told the Times in 2010. “But then people get used to it.”

In a statement, Brown hailed Rosenfeld for his work in shaping California’s modern-day energy habits. “Art Rosenfeld helped make California the world leader in energy efficiency,” said Brown, who is serving a second stint as governor. “His pathbreaking ideas transformed our energy sector from one of massive waste to increasingly elegant efficiency.”

Arthur Hinton Rosenfeld Jr. was born in Birmingham, Alabama, on June 22, 1926. He grew up in New Orleans until his father, an agronomist and sugar-cane expert, moved the family to Egypt when the future physicist was 6.

While abroad, he was introduced to a more conservative style of energy consumption. “Europeans only used half as much energy per dollar” of gross domestic product, he told the Times, “and it was clear that their lifestyle was as good as ours.”

In 1944, at age 18, Dr. Rosenfeld earned a bachelor’s degree in industrial physics from Virginia Tech. He taught radar operators in Chicago for two years during World War II before beginning graduate studies in physics at the University of Chicago, where he studied under Enrico Fermi — who developed the world’s first nuclear reactor — and earned a doctorate in 1954.

Rosenfeld joined UC Berkeley that year, working at what is now the Lawrence Berkeley National Laboratory and collaborating with fellow physicist Luis Alvarez. When Alvarez won the Nobel Prize for physics in 1968, he invited Rosenfeld to the ceremony in Stockholm.

In addition to his research, Rosenfeld had several stints in government. During the presidency of Bill Clinton, he was a senior adviser on energy efficiency at the Energy Department, working on climate change and efficiency issues. He served on the California Energy Commission, the state energy policy and planning organization, from 2000 to 2010 and then was named a member of the federal Secretary of Energy Advisory Board.

His wife of 53 years, the former Roselyn Bernheim, died in 2009. Survivors include two daughters, both doctors — Margaret Rosenfeld of Seattle and Anne Hansen of Belmont, Massachusetts — and six grandchildren.

Rosenfeld received the Energy Department’s Enrico Fermi Award in 2006 and the National Medal of Technology and Innovation from President Barack Obama in 2013.

He was also honored by 54 of his colleagues, who in 2010 co-authored a paper that proposed a new unit of measurement equivalent to the amount of energy produced by a 500 megawatt coal-fired power plant each year. It would, the paper promised, be a convenient way to perform back-of-the-envelope calculations about the elimination of proposed power plants.

The scientists proposed that it be called the Rosenfeld.