Hybrid-electric vehicles have been alternately portrayed as the saviours of modern transportation or the last gasp of the dying oil-based economy. Either way, Toyota has capitalized on their popularity with its world-beating Prius hybrid, and is aiming to increase the success of the hybrid further still by selling one million hybrid-electric vehicles per year by the first few years of the next decade.

High on the list of tools Toyota plans to use to reach its lofty goal is the plug-in hybrid. As evidenced at the Frankfurt Motor Show this year, the plug-in hybrid model is the next step for the hybrid industry. Testing of plug-in hybrids is already scheduled to begin soon in the U.S., Europe and Japan, reports Automotive News. Toyota’s plug-in hybrids will sport lithium-ion batteries developed in conjunction with Panasonic EV Energy Co. to help maximize electric capacity.

Honda, on the other hand, is “not really convinced” that plug-in hyrids are the way of the future. Costs are higher and efficiency is not much different from current non-plug-in hybrids except over short distances, and even then only if the vehicle is run in electric-only mode. Toyota itself has expressed concern that plug-ins are too costly to justify production, but it has come to believe that smaller, lighter lithium-ion batteries will fix that problem.

In addition to hybridizing its existing line-up, Toyota will introduce new, hybrid-only models in hopes to meet its annual sales goal of one million hybrids.