02/10/2015 11:48 am ET Updated Apr 12, 2015

Hybrid Owners: Stay Out of the Carpool Lane

Mitch Diamond via Getty Images

If you have a hybrid, plug-in hybrid or electric vehicle (EV), you should not be driving in the carpool or HOV lanes. Even if your home state allows you to legally drive in the carpool lane with the driver as the car's only occupant, you shouldn't do it. Here's why:

At higher speeds, like those experienced in a free-flowing carpool lane, hybrids, plug-in hybrids and EVs are less efficient. These modern fuel-sippers and electric vehicles are most efficient at low to moderate speeds, or even in bumper-to-bumper traffic. If your goal in buying a hybrid or EV is to use less gasoline, save money or lessen our country's dependence on foreign oil, you're missing the boat if you opt into the faster-moving HOV lane.

The Experts Say...

According to Ford's Director of Electrified Powertrain Engineering, Kevin Layden:

Hybrids can prove more efficient in stop-and-go driving, where they can take better advantage of regenerative braking and electric-only operation, as the kinetic energy typically lost in braking is captured and used to accelerate the vehicle. ... At steady highway speeds, much of a vehicle's energy is lost to wind resistance and rotating friction, which can't be recovered by hybrid systems.

This is even true of electric cars, such as the Nissan Leaf. Cars like the Leaf, Toyota Prius and Ford Fusion Energi have those regenerative brakes Layden mentioned. But there's more to it than that.

Brian Brockman with Nissan USA says:

If you look at the [Environmental Protection Agency] cycles, Leaf is more efficient in city driving than highway. That is mainly due to aerodynamic drag at higher speeds. So 40-mile-per-hour cruising is going to be more efficient than 70 miles per hour.

Sam Butto, Senior Product Communications Specialist with Toyota says:

When driving in city conditions at lower speeds, the [hybrid] system can utilize electric operation more often than highway driving to enhance fuel economy.

Translation: Driving slower or in stop-and-go conditions uses less energy than driving a higher speed.

Plug It In

For two months I've been driving a Ford Fusion Energi. Energi is just a brand name and Ford-speak for "plug-in hybrid." A plug-in hybrid uses a combination of battery power and gasoline to move the car along. Hybrids like these can be plugged into a standard wall outlet or a higher-capacity quick charger.

Plugging in a hybrid allows it to operate solely on electricity for a period of time, giving you the benefit of driving an EV with the added bonus of a backup gas engine for longer trips. EV range varies from car to car; for example, the Fusion Energi has a stated EV range of about 21 miles, although I've seen it as high as 26 miles.

For drivers of fully electric cars like the Kia Soul EV, Ford Focus Electric and Nissan Leaf, driving in slow-moving traffic means the time between charging will be less frequent. It's true: Cars like these will never use gasoline, but less time between charge-ups is just another way of using less. Remember, electricity has to come from somewhere too. In some cases it means building a dam or a nuclear reactor or burning coal.

Firsthand Knowledge

Last week my normal commute to work was affected by a minor accident on a busy freeway. Traffic crawled along as the wreckage was cleared, and the drivers exchanged insurance information. The flow of traffic, however, never really recovered; it stayed slow for most of the morning. Upon arriving at work, I found that the Fusion Energi had 11 miles of electric range remaining, when I normally only have about three or four miles. By driving at lower speeds in stop-and-go traffic, I had more than double the range or energy I'd have had left after my normal, higher-speed commute.

If you're truly trying to live as green as possible, embrace the slower speeds and decline the fast-moving carpool lane. By opting to jump in the fast-moving HOV lane, you're undermining your efforts to help the planet.

Of course, it's possible that you may place less value on reducing your consumption and pollution than you do on other activities, like spending time with your family or earning more money. I might not agree, but you're free to make your own choices. Just make sure you don't point fingers at others who are making the exact same kinds of choices as you by opting to live far from work, buying a full-size pickup or not driving a hybrid.