General Motors has installed 401 electric vehicle charging stations at its US production and business facilities.

More than 20 percent of the stations use electricity generated from solar canopies to help charge employee vehicles.

The company says the majority of the stations are located at GM’s large engineering and corporate facilities in Michigan, where employee EV ownership is growing. All charge stations are available free of charge to GM employees and visitors.

In addition to the workplace charging, GM has another 400 charge spots dedicated exclusively to vehicle development and testing. Chevrolet and Cadillac dealers have installed approximately 5,900 charge stations at their locations for owner use — 17 of these dealerships use solar charging canopies.

GM’s charging count follows the Department of Energy’s announcement that 75 businesses have committed to participate in its Workplace Charging Challenge to install charging stations for their employees.

The Workplace Charging Challenge, of which GM is a founding member, seeks to persuade America’s employers to commit to provide electric vehicle charging access to employees.

Earlier this month GM said its fleet of fuel cell vehicles has passed 3 million miles of hydrogen-powered, real-world driving, avoiding 157,894 gallons of gasoline consumption.