“The button” is one of the many ways that makers of plug-in hybrids use to outperform its rivals. What consumers typically look at when choosing a model are combined fuel economy, the electric range, acceleration and recharging time. If a plug-in hybrid has “the button,” the driver can choose to keep the vehicle in electric mode or block it from switching to battery power.
This feature is available as standard on the Opel/Vauxhall Ampera and Ford C-Max Energi, as well as plug-in hybrid versions of the redesigned Ford Fusion and Honda Accord. The Ampera will start selling later this month, while the Ford and Honda models will arrive in dealerships later this year. This year in Europe is the targeted sale date of a Volvo V60 powered by a diesel-electric plug-in hybrid.
This model has “the button." According to Mark Reuss, General Motors' North American president, he hopes that this feature will be offered on the Chevrolet Volt. Reuss explained that in the U.S., GM wasn’t allowed to offer "the button" on the Volt because of an EPA issue for determining fuel economy when the car was certified. No explanation was provided. All its models in Europe have "the button." If a plug-in hybrid doesn’t have “the button,” its computer determines when the powertrain would operate in pure electric mode, hybrid or depend on gasoline.
This hands-off system studies vehicle speed, the driver's driving style, as well as other factors to find the best mode for optimum fuel economy and acceleration. With "the button," the driver could choose to use all electric in the city while he uses gasoline on the highway. When the electric charge runs low at a certain point, the system instantly switches to the hybrid or gasoline mode.
This suggests that fuel economy may be improved by “the button” since the driver could keep the vehicle in gasoline mode during highway trips and go pure electric in the city. When asked about the question of whether overall miles per gallon numbers will increase, GM said that it will depend on the driver's skills at boosting mpg. GM has said that it won’t be promoting "the button" as a way to boost fuel economy.