The Toyota Prius Plug-in Hybrid is a variant of the fourth-generation Toyota Prius hybrid that is capable of operating in all-electric mode. Unlike the regular Prius hybrid, the Prius Plug-in Hybrid has a larger lithium-ion battery pack that can be recharged using an external electricity source. As a result, in all-electric mode, the Toyota Prius Plug-in Hybrid can travel up to 22 miles without the use of the gas engine. As with the regular Toyota Prius hybrid, the Prius Plug-in Hybrid can travel further distances using a combination of gasoline and electric power.