Plug-In Hybrids – Overview

How would you like to run your car for less than $1 per gallon, with much lower emissions? Impossible?

Not according to Dr. Andy Frank, Professor of Engineering at the University of California at Davis and Felix Kramer of The California Cars Initiative (CalCars). Frank and Kramer are encouraging the development of the “gas-optional” or “plug-in” hybrid (PHEV), which yields dramatic gains in fuel economy.

Ironically, just when the American public is finally starting to understand that you don’t have to plug hybrid cars in, here comes the plug-in hybrid. With the plug-in hybrid, you still will not be required to plug the car in—but you’ll have the option. As a result, drivers will get all the benefits of an electric car, without the biggest drawback: limited range. You’ll be able to go all-electric for the vast majority of your driving that takes place close to home. When the electric charge runs out, a downsized gas engine kicks in and your car drives like a regular hybrid.

Staying in Stealth Mode

Many hybrid car drivers enjoy keeping the car in all-electric “stealth” mode, when the car is in slow stop-and-go traffic. Plug-ins would extend the stealth mode for the lion’s share of our local driving.

The potential advantages are enormous. Consider:

  • A hybrid gets about twice the fuel economy as a conventional car of the same size and capacity
  • A plug-in hybrid will get about twice the fuel economy of a hybrid
  • A plug-in hybrid, running on biofuel (e.g., 85 percent ethanol) could almost entirely eliminate its use of petroleum

What are the naysayers saying about plug-in hybrids? And how do Frank and Kramer respond?

The extra batteries will weigh too much.
Response: The extra weight of the batteries will be offset somewhat by the reduced weight of the gas engine. At high speeds in particular, fuel efficiency is affected primarily by aerodynamics—the added weight of the equivalent of one or two additional passengers reduces MPG minimally.

The extra batteries will cost too much.
Response: If sold in high volumes by carmakers, more powerful and cheaper nickel metal hydride or lithium ion batteries could be sold at prices only a few thousand dollars above that of today’s hybrids. Recharging will take place mostly at night during cheaper off-peak hours. Counting purchases, fuel and service, total lifetime cost of ownership will be lower than a gas car.

Producing power from the grid (to charge the cars) will produce additional emissions.
Response: What the industry calls “well-to-wheel” emissions (including greenhouse gases) for grid-powered vehicles is far lower than gasoline, even for the American power grid (which is 50 percent coal). Cars charging off-peak will use power from plants that can’t turn off at night. Many parts of the country get most of their power from cleaner sources such as natural gas and hydropower. It’s far easier to improve centralized power stations than millions of aging cars. Finally, plug-in hybrids recharged from rooftop photovoltaic systems would have virtually zero emission.

Future Benefit of Vehicle-to-Grid Connection

Someday, the larger battery packs used in plug-in hybrids could juggle power back and forth from the car to your household current. If adopted on a widespread basis, a fleet of plug-in (a.k.a. “gridable” hybrids) could offer what are called “regulatory services” (keeping voltages steady, etc.) to a modernized electric power grid. It is estimated that what’s called “V2G” could benefit individual car owners by as much as $2,000 to $3,000 per year for the use of their energy storage capacity—offsetting their purchase and operating costs.

What Plug-in Hybrid Vehicles Exist?

Professor Frank’s Hybrid Center has built a half-dozen PHEVs, including a number of heavy SUVs. CalCars converted a Prius in late 2004. And now a number of companies are offering plug-in conversion services or kits.

Who’s Touting Plug-in Hybrids?

CalCars is working to promote awareness of the technology and demonstrate a market for plug-in hybrids in hopes Toyota and other manufacturers will build them. In Washington, Set America Free and Securing America’s Future Energy, the Apollo Alliance and others are among the groups promoting them for their energy security, environmental and economic development benefits. And a broad effort, spearheaded by Austin Energy, is getting under way to gain commitments from utilities and state and local governments to buy PHEVs for their fleets.

Will Auto Makers Produce Plug-in Hybrids?

Despite a number of announcements from leading car companies, and some exciting concept vehicles shown at auto shows, plug-in hybrids are not yet available. We will track the most viable PHEV plans and post to the plug-in hybrid section of HybridCars.com.


  • art3427

    I am VERY enthusiastic about plug hybrids. My wife has a 2001 Jeep Grand Cherokee. We are considering replacing it with some sort of hybrid combo in the near future.

    One issue has not been addressed in hybrid fuel discussion. Petro based fuel prices reflect a significant tax source for both state and federal coffers. As we switch to a non-petro culture these revenues will also decrease. How will the “powers that be” make up this revenue short fall? Could we end up with electric bills that rival present petro based fuel prices?