Hawaiian Electric Co. launched an online calculator Monday that helps potential electric vehicle owners compare the cost to charge a vehicle at home with the cost of filling it up at the pump.

EV buyers can use the online calculator — hawaiianelectric.com/wattplanforEV— called WattPlan for Electric Vehicles on their desktop computer, laptop, tablet or smartphone to compare the make and model of plug-in electric vehicle with an internal combustion engine vehicle.

After selecting the two vehicles to compare and typing in their average daily commute, drivers can compare their monthly electrical bill if they were to charge an EV against their monthly electrical bill combined with current gasoline prices. Drivers can alter the settings to calculate the cost of charging at home or using public charging stations. The tool provides a map of where charging stations are in the state.

The calculator breaks down how the time a vehicle is charged can affect the overall energy cost. It also shows the incentives available to EV drivers and the environmental benefits of driving an EV compared with a gasoline car.

“We encourage prospective electric vehicle owners to consider their entire home energy bill — electricity plus gasoline — when making this decision,” said Alan Oshima, the utilities president and CEO, in a statement. “While adding an electric vehicle may slightly increase your monthly electric bill, that will likely be more than offset by buying little or no gasoline. That is my experience as a new electric vehicle owner.”