General Motors said it now expects to sell 16,000 Chevy Volt and Opel Ampera (a German model of the Chevy Volt) vehicles, a jump from its previous sales targets for the first full year of its plug-in electric hybrid.

That’s despite GM’s plan to ship more cars to dealerships as demonstration models to bring in new electric car buyers. General Motors has shipped around 1,700 Volts since the vehicle went on sale last year. There is more than enough demand for plug-in electric cars and electric hybrid vehicles like the Volt and the Nissan Leaf, but manufacturers have struggled to meet that demand due to production delays and strategic moves to make the cars more appealing to mainstream car buyers.

General Motors also said it will shut down the plant responsible for manufacturing the Volt and Ampera in Detroit for four weeks to retool it. That would allow the plant to focus on production of the 2012 model of the Volt and Ampera but could put even more strain on an already cramped supply line of plug-in electric hybrids.

The Volt has a traditional internal combustion engine and an engine powered by a battery jammed into the same vehicle. The car can run around 35 miles off battery power before the internal combustion engine kicks in, giving the car a total range north of 300 miles on a full charge and full tank of gas. It’s one of the cheaper electric cars on the market. The Volt retails for around $40,000, compared to the super high-class Tesla Roadster that retails for more than $100,000.

GM earlier said it expected to ship around 10,000 Volts this year and said it would sell 15,000 Volts and Amperas together. Those figures are slightly ahead of what GM would need in order to meet the ambitious targets set by the U.S government, which wants more than 1 million electric cars on the road by 2015. But that is assuming a majority of the sales occur in the United States — while GM’s new projection includes international sales of the Ampera. The U.S. government expects GM to sell around 500,000 Volts by 2015 and Nissan to sell 300,000 Leafs by 2015, according to the report.