The Dirty Secrets about PHEV

1st generation Toyota Prius (1997/12 - 2000/5)
Image via Wikipedia

As I sip my first cup of coffee this morning trying to wake up I stumble upon a story by John Peterson on Seeking Alpha about the true cost of plug in electric hybrid vehicles.

It’s true that the hybrid cars we’ve come to know are changing the transportation landscape, but Peterson was saying that going the next step to a complete battery powered PHEV might not make sense.

Here’s the table that woke me up:

Electric Drives Miles/kWh of Battery Capacity Camry Leaf Roadster
10-year mileage 125,000 125,000 125,000
Gasoline miles 88,710 0 0
Efficiency miles 36,290
Electric utility miles 125,000 125,000
Battery Pack kWh 1.3 24 56
Electric miles per kWh 27,916 5,208 2,232
Fuel saved per kWh 931 174 74

Never mind the cost differences for a moment, the lesson in the story was that the Prius or, in this case, Camry gas-hybrid was substantially more efficient at saving fuel and making a positive environmental contribution than that shiny new Chevy Volt or Nissan Leaf.

So I Googled environmental impacts of PHEV and found plenty of research done by the national labs, Electric Power Research Institute, Pew Climate Study Center and others that backed up Peterson’s conclusions even though his story provided no references to ball back on.

It turns out there are a few dirty secrets to consider before you buy a PHEV:

Efficiency versus Substitution Trade-off. The Camry hybrid uses its battery powered hybrid capabilities to make its gasoline engine more efficient.  After more than ten years and millions of miles of experience with hybrid engines Toyota and others have “pimped them” to perform quite well.  Consumer Reports this month has a story about the long term performance of a ten year old Toyota Prius still going story with little loss of battery recharge capability. PHEV, on the other hand, are a substitution for the combustion engine and thus displace gasoline use with electricity use to power the car.

Emissions Reduction Realities for PHEV. The PHEV is only as clean as the underlying source of the electricity used to recharge the battery.  If you plug that car in overnight to recharge it for the next day’s commute you are probably using electricity produced from baseload sources either coal or nuclear power which run virtually all the time.  The PHEV isn’t bad on the environment if it gets its power from the nuke plant but if the power comes from coal fired generation it isn’t saving much in emissions reduction but it will drive up your cost of driving.

Yes, I know, the image behind the PHEVs is they will be powered by wind or solar energy, but the sun rarely shines at night when you and your car are safely tucked in bed.  Most renewable sources are intermittent and thus require back-up from baseload generation or from load-following power plants typically run on natural gas.

Reduce Oil Imports for Energy Security Rationale. You might belong to the club that rationalizes the PHEV purchase on the grounds that you want to reduce America’s dependence upon imported oil by using less gasoline.  If that is your true motive and economics matter, the better choice might be to pimp your vehicle to run on compressed natural gas.  Yes, it still produces GHG emissions but gas is cleaner than coal and the US has plenty of it.

So what

The more we know about the full economic and environmental story behind plug-in electric hybrid vehicles the less of a game changer they appear to be for the future. Peterson’s table shows that the PHEV is simply not yet a good choice either economically or for the environment because substituting a less efficient electric source for a more efficient hybrid gas-battery alternative is not economic nor the most environmentally responsible choice today if that is what is driving your purchasing decision.

The good news is that efficiency is our friend and it works much more cost effectively than many of the new technology substitutions coming to market.  This is true in transport just as it is true in energy use in other segments of the economy from our homes, offices and factories.

Even better news is that we can achieve substantial reductions in greenhouse gas emissions without the necessity of imposing carbon taxes, cap and trade legislation and other onerous burdens on our fragile economy by making more efficient use of gasoline through hybrid technology and better electronics.

The Pew Climate Center, the University of Michigan, and  others studying PHEV impacts are finding generally consistent results that to dramatically cut emissions from the transportation sector, we must both move to low carbon fuels (including electricity, which has zero GHG emissions from the tailpipe) and reduce the carbon intensity of the electrical grid.

That means a full frontal assault on the way Americans live our lives with more onerous or intrusive regulations, taxes and policies.  Maybe that is why more recent studies of the impacts of PHEV are telling us the grid has plenty of capacity to handle the expected market share growth of PHEV and that growth is increasingly expected to be a slow climb over a long time.



  1. … and nobody talks about the cost and environmental impact of manufacturing the batteries and electric motors …. or recycling them.

  2. Gary, Is there a place in here for the best of both. Ie Plug-in Hybrid Electric Vehicles. It appears that the comparison you’ve picked up is between Hybrid (ie non-plug in) and non-Hybrid electric vehicles driven solely off of the grid.

    I think the base analysis is spot on. Until there are low carbon (nuclear) and cheap (nuclear without Billions in Nimby drag) methods of producing bountiful electricity during the night and having it soaked up by gracious little Plug in Electrics, the Plug in Hybrid soaking up overnight non-peak loads from coal plants and spending what time it must on gasoline power seems the most efficient and flexible alternative.

    By the way, don’t underestimate flexibility. In analyzing driving patterns, you hear the electric proponents discussing average driving. All true, but the outliers are a problem. You commute 10 miles, then once a month drive 200 miles to a customer site or to ski or to go to the beach. Do you go rent a car? Use your second car? Oh, we can only sell plug in electrics to folks who have a second car? Oh, we wait until Shai’s battery exchange stations are up and running on the highways and byways of America? I think you’re looking at a limited market for true plug in electrics for awhile.

  3. Dan: The “sweet spot” for PHEVs is likely fleet vehicles where limited range makes it practicable near term although compressed natural gas may actually be more cost effective especially where range is an issue. That is the FedEx and UPS solution.

    I’m all in favor of soaking up cheap off peak resources at night and time shifting by using them during the day for PHEVs which probably works for most commuters. The 200 mile occasional trip means you swap cars with your spouse for the day or rent one.

    Long term I think the best of both worlds answer is use gas-electric hybrids to reduce gasoline consumption, reduce oil imports by displacement, and gain emissions reductions. If PHEVs must compete without subsidies with gas/electric hybrids they will get better range at lower costs or lose out.

    I think improving energy efficiency (gas/electric hybrid) is a better policy goal than electric substitution (PHEV) which drives up costs and does not reduce emissions.

  4. As Dan Drechsel pointed out you’re not talking about PHEV’s. You’re talking about EVs, with no gas engine. The PHEV would be just like the Camry example except that it always starts the day with a full battery pack. What is its efficiency? Is there a benefit in that if the PHEV is still home at 1 PM it can feed the power back into the grid (time-shift)? Assuming of course the millions or billions of dollars in supporting grid control investments…..

  5. One thing I never see in these calculations is how much (coal-fired) electricity it took to extract, refine, and deliver a gallon of gas for a combustion engine… if it’s substantial, then using that electricity directly in an EV/PHEV instead has benefits too. I don’t know if it’s possible to quantify…

    1. Eric: The argument over externalities is akin to calculating how many angels can dance on the head of a pin. If you insist on calculating the coal externalities then I could respond by asking to calculate the cost of environmental process externalities or some other arcane factor. This tit for tat is good intellectual exercise and perhaps it will reduce our probability of getting Alzheimer’s or some other dementia but it does not solve our basic problem. To grow our economy we need affordable, reliable energy supply. The job of energy suppliers is to meet demand not re-engineer it. When the market driven price of the next increment of energy supply is higher than we want to pay we will change our demand behaviors and the price will come down.

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