Experts weigh in, but I think to stay competitive with the Nissan LEAF a modest price drop should accompany some value-added tweaks. An alternative, says dealer Leo Karl III, is a new entry-level model.

April was another good month for the Nissan LEAF, which moved 1,936 units nationwide to post its second best month of sales since hitting the market in late 2010.

Speaking at Fortune's Brainstorm Green conference, G.M. chief executive Dan Akerson spoke about the company's sustainability efforts and greener vehicles. He said the next-generation Chevy Volt, due in 2015 or 2016, would cost less to build and finally be profitable.

Nissan LEAF sales soared to a record high in March 2013, beating the previous high-water mark by a substantial margin. Meanwhile, Chevy Volt sales remained relatively stable.

According to AAA, the Chevrolet Volt is among the best commuter vehicles in the United States. Experts from the membership-based travel organization evaluate hundreds of vehicles each year based on comfort, performance and fuel efficiency.