Plug-in Hybrid FAQ

Climate Progress has blogged on Plug-in Hybrid Elective Vehicles (PHEVs) many times because they are an important part of the climate solution and because electricity is the only alternative fuel that can lead to energy independence. But certain questions keep coming up in comments, so here’s a short FAQ.

What is a Plug-in Hybrid Electric Vehicle (PHEV)? A PHEV is like a regular hybrid electric vehicle (HEV) but with a larger battery pack and a plug so the batteries can be charged from standard household current. Thus the vehicle is dual-fuel: your driving can be powered by either electricity, gasoline, or both. For more, see CalCars’ All About Plug-In Hybrids and Wikipedia’s Plug-In Hybrids. A number after the PHEV acronym indicates the electric range of the vehicle, so a PHEV-20 can operate on electricity instead of gasoline for 20 miles. Why would I want to plug in my car? Fueling your car with electricity is about 5 times cheaper than fueling it with gasoline. That is like buying gasoline at less than $1 per gallon. It also reduces your greenhouse pollution and helps reduce crude oil imports. If fueling my car with electricity is so cheap, why bother with gasoline? Initially PHEVs will be able to run 10–60 miles solely on electricity. When you need to go further, the car can seamlessly and automatically switch to gasoline. Charging the batteries is optional (but much cheaper per mile). Why can’t PHEVs have a higher electric range?


They could, but they wouldn’t be as cost-effective. Most people drive less than 40 miles a day (see chart), and paying for range that is infrequently used adds to the cost without significant fuel savings. Pure Battery Electric Vehicles (BEVs) have ranges up to 250 miles, but large battery packs are expensive (though declining in price each year), so when the gas tank is present it makes sense to use it. For electricity the fuel is cheap but the tank (the battery pack) is expensive. For gasoline the fuel is expensive but the tank is cheap. PHEVs combine the best of these by using electricity for your everyday driving, and using gasoline for the less common long trips. What if I want to take a family vacation, and drive hundreds of miles? Plug-in hybrid electric vehicles are exactly like hybrids when taken on long trips — they are powered by gasoline from the tank. They use much less gasoline than conventional vehicles because of hybrid efficiency. The occasional family trip is one reason that PHEV-20s, for example, are projected to cut gasoline consumption only in half. Won’t PHEVs require us to build even more power plants?

Not at first. PHEVs will be programmed to charge at night, when electricity demand is low. (You’ll plug it in when you get home, and the car will know when to charge.) One of the U.S. Department of Energy’s labs, the Pacific Northwest National Laboratory, looked at how many plug-in vehicles today’s grid support without modification, and concluded that 73% of cars, pickup trucks, SUVs, and vans could be supported by the existing infrastructure. This is made clear by the picture above from the Electric Power Research Institute (EPRI), a utility-funded lab. Why do PHEVs reduce greenhouse pollution?

A study by EPRI, the California Air Resources Board, the National Renewable Energy Laboratory, Argonne National Laboratory, and others (5.3MB PDF) concluded that plug-in hybrids produced substantially lower greenhouse gas emissions than either conventional gasoline cars or unplugged hybrids. The reduction in emissions results from electric operation being much more efficient than gasoline operation. Don’t PHEVs and BEVs just shift pollution from the tailpipe to power plants? No. The proper comparison between vehicle types is the “wells-to-wheels” basis, where the pollution from extracting the raw materials, shipping, transformation (e.g. refining), and use are added. BEVs and PHEVs running on electricity have zero tailpipe emissions, but there are still mining and power plant emissions. Those emissions are however much lower than the corresponding crude oil extraction, refining, and tailpipe emissions. Pollution here includes greenhouse gases such as carbon-dioxide. The grid is getting cleaner each year, and will continue to do so as we replace fossil power plants with renewables, while a gasoline car gets dirtier as it ages. Fueling a car on gasoline made from coal (Coal-To-Liquids or CTL) emits twice as much greenhouse gas as gasoline from crude oil. Why is fueling a PHEV from coal electricity better than gasoline? Two reasons: (1) Electric motors are extremely efficient compared to internal combustion engines, and this efficiency more than compensates for the dirtiness of coal. (2) The U.S. grid is only 49% coal (natural gas is 20%, nuclear is 20%, hydro is 7%, and other renewables are 2.4%). Thus power to charge PHEVs is not all from coal, and some is from zero emission sources. When and where can I buy one? PHEVs are not yet available from major automakers, but will be in 2 years. There are kits and companies that will convert hybrids to PHEVs. Please see CalCars’ How Carmakers are Responding to the Plug-In Hybrid Opportunity for more information, and start telling car dealers “no-plug, no-deal”. Don’t PHEVs cost more to buy? How long does it take to break even? PHEVs require a larger battery pack compared to a hybrid, and the additional batteries do add cost. A mid-size sedan with 20 miles of electric range (a PHEV-20) would require 6.7 kWh of additional batteries, costing an extra $2000. If this amount were financed with a 5-year auto loan at 5.5%, the monthly payment would be $38. Using today’s gasoline prices ($4.08/gallon), electric operation might reduce the car’s monthly fuel expenses by $57, leaving a net savings of $19. As gasoline prices increase, the savings increase. With a loan or lease paying for the batteries, small savings begin in the first month, and increase at the end of the loan term. The resale value of the car is also increased. Why are PHEVs good for the country, not just my wallet?

Converting ten million conventional vehicles to hybrids reduces U.S. consumption of gasoline by 1.5% a year. Convert those hybrids to PHEV-20s and we reduce our gasoline consumption an additional 1.5%. Doing both, going from conventional vehicles directly to PHEVs reduces consumption by 3.0% a year. Sell 10 million PHEVs each year, and the savings accumulate (3% the first year, 6% the next, and so on), reducing our imports (66% of our gasoline is from imported crude). The reduction in gasoline consumption not only saves PHEV drivers money, it also reduces the U.S. trade deficit, and makes us less dependent on foreign producers. Many national security experts see plug-in hybrids as crucial to U.S. security, including former Secretary of State George Shultz, former CIA Director R. James Woolsey, former National Security Advisor Robert McFarlane, and many Representatives and Senators. See Oil and Security by George Shultz and R. James Woolsey and the Set America Free Coalition for more information. Are the batteries ready? Yes. According to EPRI, “battery durability testing sponsored jointly by EPRI and Southern California Edison demonstrate that current lithium-ion batteries are likely to retain sufficient capacity for more than 3000 dynamic deep-discharge cycles — about 10–12 years of typical driving.” The excuse “the batteries aren’t ready” has been used frequently because it is convenient, and few people bother to check. Any manufacturer sells what it has, and automakers are no different. When there are failures of planning in the board room, it is convenient for a manufacturer not to admit their mistake, but to blame the lack of a product on something beyond their control. That is PR. The current absence of plug-in vehicles from America’s showrooms has been conveniently blamed on the batteries. In reality, existing, proven NiMH batteries, such as found in hybrids and BEVs could easily power PHEVs. However, automakers would like to switch from NiMH to Li-Ion batteries for PHEVs because they are lighter, smaller, and potentially cheaper. Common Li-Ion batteries (Lithium-Cobalt), such as found in cell phones and laptops have lifetime and safety issues, which allowed the automakers to claim lack of readiness. However, other Li-Ion chemistries have existed for some time, so this claim was not accurate. For example, Lithium-Iron-Phosphate batteries are inherently safe and will last the lifetime of a vehicle. Also, the issues with Lithium-Cobalt batteries can be solved with the addition of other elements such as nickel and manganese. For example, Sanyo uses a mixture of Ni, Mn, and Co for the positive electrode, thereby producing a safer battery that exhibits power retention ratio of 80% or higher after 10,000 cycles (10–15 years in a hybrid vehicle). What about charging PHEVs from renewable energy sources, such as wind or solar? Wind and solar are excellent sources of electricity for PHEVs because PHEVs could be designed to take power when it is available, and not be bothered by intermittency. Cars are typically in use 5% of the day, and parked 95% of the time. Charging from a normal wall outlet might take 30% of the day. That difference represents flexibility to charge when wind or solar power are available. It is also not necessary to get a full charge, there is always gasoline as a backup. Where can I find more information? A few of the many previous Climate Progress posts are listed below. The CalCars FAQ covers a few more questions not covered here. The previously cited Pacific Northwest National Lab report is filled with technical details. Two EPRI Journal articles cover PHEVs: Plug-In Hybrids on the Horizon: Building a Business Case (1.7MB PDF) and The Plug-in Hybrid Vehicle: Beyond Gasoline (4MB PDF). A joint assessment, Environmental Assessment of Plug-In Hybrid Electric Vehicles, by EPRI and the National Resources Defense Council (NRDC) is very detailed. Related posts:

External references:

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