A Guide to Home Charging of Plug-in Cars

GM's wall-mounted 240-volt charger, which can charge the Chevrolet Volt in about three hours, meets the latest auto industry standards.

The majority of plug-in vehicle owners are expected to primarily charge their vehicles at home because of its obvious convenience. Vehicles could be charged via a standard110 volt outlet, but safety concerns—for both the vehicles and the buildings—have prompted the passing of building codes that require equipment that monitors the charging process. Plugging into a standard outlet without additional equipment is not advisable, and may void the battery warranty.

Plug-in vehicles draw a lot of power—more than any other device in the home, with the possible exception of large air conditioners. If vehicles are plugged into the same circuit as another appliance, there is the potential to blow fuses or damage equipment. Therefore, plug-in vehicle companies will require that vehicles have their own a dedicated circuit, which is installed by an electrician.

Two varieties of chargers made by Aerovironment for the Nissan Leaf.

Some Assembly Required

To ensure that the batteries are provided with consistent power and are not damaged by fluctuations such as power surges, or from overcharging the batteries, special charging equipment is required. Since the world loves acronyms, this equipment goes by the name EVSE, or electric vehicle supply equipment. The EVSE setup includes a connector for plugging in the vehicle's onboard charging equipment, a charger, and a "wall box" to manage power that includes a display screen that provides information including the state (percentage) of charge.

This charging equipment will enable vehicles to be charged at multiple speeds, known as level I and II charging. (A Level III charging standard is also being developed, but the high power required is not permitted by some residential building codes, and would be cost-prohibitive for most homeowners.) Because of the timesavings, it is expected that most folks will purchase Level II charging equipment. Plug-in vehicle owners will probably be able to program charging equipment to delay charging until less-expensive off peak hours, or to specify only charging when the price of electricity falls below a set level.

Some utilities will offer smart meters that coordinates with charging equipment. The meters will be able to slow down or pause charging if the grid begins to get overwhelmed with power demand. This is considered an essential function for preventing blackouts or brownouts, which would make everyone in your neighborhood unhappy.

While these costs may seem hefty on top of the vehicles themselves, the federal government has established a 50 percent tax credit—up to $2,000—towards the cost of charging equipment. Solar-powered charging equipment is also now available for those who desire true emissions-free driving, and it is eligible for a separate 30 percent tax credit. A few states offer their own tax credits for plug-in vehicle charging equipment.

Getting Started

Auto manufacturers will work with their dealers to provide everything you ever needed to know about vehicle charging—and then some. They will recommend charging equipment companies, and will work with utilities to help direct you to electricians to install the equipment.

Currently charging equipment is produced by specialty companies that you probably haven't heard of, such as Coulomb Technologies, Aerovironment or Ecotality, but it is a safe bet that larger name brand companies and smaller niche players will enter the market.