If you are assigned a company car for business purposes and you are not allowed to use it for personal use, then it is not taxable to you.
If you are allowed free use of a company owned vehicle for personal purposes, then the value of the personal usage must be included in your taxable income. Your employer must treat it as if it was a cash bonus of the same value, and withhold state and federal income taxes and employment taxes, and include the value of the car in your taxable income on your W-2.
If you take the car at home at night, and use it for commuting, that is considered personal use, unless there is a business reason that you must have the car at home. (For example, if you are a traveling salesman and you need to see clients first thing in the morning, and it would be too time-consuming to drive to work with your personal vehicle and then pick up the company car.) If commuting is the only personal use allowed for the car, the employer may assign a value of $1.50 per trip.
If you are allowed to use the vehicle for more than just commuting, the IRS offers the employer three different ways of calculating the value that must be included in your taxable wages. I’m not going to go into detail on those methods for now.
The bottom line is that you need to ask your employer how they are going to calculate the value of the personal use and what personal use they are going to assign to you as wages. Then, the income tax you will pay is exactly the same as the tax you would pay if the employer gave you a cash raise or cash bonus in the same amount as the value of the car.
The fact that the car is electric has no affect on the value that is assigned to you as wages.
