General Motors is planning this year to build as many as 36,000 Chevrolet Volts and other plug- in hybrids for worldwide delivery, 20 percent more than in 2012, two people familiar with the effort said.

GM is planning to build 1,500 to 3,000 of the fuel- efficient vehicles a month, said the people, who didn’t want to be identified because the target isn’t public. GM sold about 30,000 Volt and similar Opel Ampera cars globally in 2012, said Jim Cain, a company spokesman, who declined to give a target for this year.

Chief Executive Officer Dan Akerson has struggled to compete against more successful alternative-power vehicles such as Toyota’s Prius. The CEO originally touted the Volt’s gasoline-and-electric system as the technology of the future and forecast global Volt sales of 60,000 in 2012, before settling for half that amount.

The 36,000 target is “probably a doable number,” Jim Hall, principal of consultancy 2953 Analytics, said. “It will have a full calendar year in Europe” and GM will probably sell more this year now that the Volt is eligible for the car-pool lane in California, he said.

Battery-only and plug-in hybrids that meet strict California emissions rules qualify for a sticker that permits solo drivers to use the lanes with vehicles carrying multiple passengers.

The plug-in Volt can travel 38 miles (61 kilometers) on electric power before a gasoline engine engages to recharge the battery. Plug-in hybrids can also be recharged by plugging into an electrical outlet. U.S. sales of the Volt more than tripled last year to 23,461, about half of Akerson’s original target of 45,000.

After last year, which included temporary production shutdowns, the Detroit-based automaker wants to find a consistent selling rate for Volt, Cristi Landy, GM’s marketing director for small cars, said in an interview this month in Chicago.

“We had some on and off starts with the assembly plant,” she said. “California, which is our strongest market, was selling great then they would have no products. They’ve run out of products probably three or four times in the last 12 months, it’s been very frustrating.” GM produces the Volt at its Detroit-Hamtramck assembly plant.

Besides the Chevy Volt and Opel Ampera, GM plans to start production of the Cadillac ELR, a two-door plug-in hybrid that uses Volt-like technology.

CEO Akerson said during a Bloomberg Radio interview in April 2012 that he wanted to increase U.S. Volt sales to the 3,000 a month level. In June, he cut his original forecast of 60,000 worldwide and 45,000 U.S. Volt sales in 2012 to “somewhere between” 35,000 and 40,000, without specifying a breakdown by region.

Slow sales have exasperated GM executives as the Volt got entangled in U.S. presidential politics last year with Republicans criticizing it as a symbol of President Barack Obama’s auto-industry bailout.

The Volt, chosen as 2011’s North American Car of the Year, succeeded in satisfying its customers, with 92 percent of survey respondents telling Consumer Reports they would buy one again — the second straight year it ranked highest.

The Volt went on sale in 2010 with the aim of putting GM’s Chevrolet brand on the forefront of green technology globally and taking on Toyota’s mass-market Prius hybrid, which starts at $24,200. Toyota also sells a subcompact Prius c that sells for $19,080.

GM, Toyota City, Japan-based Toyota and Volkswagen AG are competing to be the top-selling automaker in the world. Toyota overtook GM last year as No. 1 while the U.S. automaker finished second, outselling VW by more than 130,000 deliveries. Wolfsburg, Germany-based VW says it wants to become the world’s biggest by 2018.

Starting at $39,145, the four-seat Volt is loaded with pricey batteries and more expensive than a similar-size gasoline compact, even with a $7,500 U.S. tax credit. The Toyota Corolla, for example, starts at $16,230.