Plug-in hybrid

A plug-in hybrid car is similar to a conventional hybrid vehicle—both use a gasoline engine as well as an electric motor. A plug-in hybrid differs primarily in that it can be plugged in to charge the batteries, while a conventional hybrid relies solely on energy generated from braking, coasting or from the gasoline engine.
However, a plug-in hybrid uses larger battery packs that can be recharged by connecting to common household electricity. Plug-in hybrids can be driven for long distances—from a few miles to as much as 40 miles—without using any gasoline. Plug-in hybrid cars are also known as plug-in hybrid electric vehicles or PHEVs. Plug-in hybrid cars that use a gas engine exclusively for recharging batteries—rather than directly powering the wheels—are also called Extended-Range Electric Vehicles or E-REVs.
Fueling a car with electricity is about 5 times cheaper than fueling it with gasoline. That is equivalent to buying gasoline at less than $1 per gallon. It also reduces greenhouse pollution and helps reduce crude oil imports. Also plug-in hybrids produced substantially lower greenhouse gas emissions than either conventional gasoline cars or unplugged hybrids. The reduction in emissions results from electric operation being much more efficient than gasoline operation. 
Criticisms.
Criticisms of the hybrid include the additional cost, weight, and size of a larger battery pack. But The extra weight of the batteries will be offset somewhat by the reduced weight of the gas engine. 
It is obvious for most people that internal combustion engine cars cannot represent the future anymore because of the oil reserves that are estimated to be finished in forty or fifty years. Obviously, Plug-in vehicles cannot be considered a short term option because we lack the needed infrastructure and capable batteries for increasing the autonomy that is currently limited. The general opinion was that, at least for the next seven or eight years, Plug-ins are not going to become the standard in hybrid vehicles and that regular HEVs will have the biggest proportion on the market.