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DOE Study: Off-Peak Production from US Grid Could Support 184.8 Million Plug-In Hybrids

A new study for the US Department of Energy finds that off-peak electricity production and transmission capacity could power 84% of the country’s 220 million vehicles if they were plug-in hybrid electric vehicles (PHEVs).

Researchers at DOE’s Pacific Northwest National Laboratory also evaluated the impact of PHEVs on foreign oil imports, the environment, electric utilities and the consumer.

This is the first review of what the impacts would be of very high market penetrations of PHEVs. It’s important to have this baseline knowledge as consumers are looking for more efficient vehicles, automakers are evaluating the market for PHEVs and battery manufacturers are working to improve battery life and performance.

—Eric Lightner, DOE’s Office of Electric Delivery and Energy Reliability

Current batteries for PHEVs could store the energy for driving the national average commute—about 33 miles round trip a day—so the study presumes that drivers would charge up overnight when demand for electricity is much lower.

Researchers found that in the Midwest and East, there is sufficient off-peak generation, transmission and distribution capacity to provide for all of today’s vehicles if they ran on batteries.

However, in the West, and specifically the Pacific Northwest, there is limited extra electricity because of the large amount of hydroelectric generation that is already heavily utilized, and increasing electricity from hydroelectric plants is difficult.

We were very conservative in looking at the idle capacity of power generation assets. The estimates didn’t include hydro, renewables or nuclear plants. It also didn’t include plants designed to meet peak demand because they don’t operate continuously. We still found that across the country 84 percent of the additional electricity demand created by PHEVs could be met by idle generation capacity.

—Michael Kintner-Meyer, PNNL

The study also looked at the impact on the environment of an all-out move to PHEVs. The added electricity would come from a combination of coal-fired and natural gas-fired plants. Even with today’s power plants emitting greenhouse gases, the overall levels would be reduced because the entire process of moving a car one mile is more efficient using electricity than producing gasoline and burning it in a car’s engine.

Total sulfur dioxide emissions would increase in the near term due to sulfur content in coal. However, urban air quality would actually improve since the pollutants are emitted from power plants that are generally located outside cities. In the long run, according to the report, the steady demand for electricity is likely to result in investments in much cleaner power plants, even if coal remains the dominant fuel for our electricity production.

With cars charging overnight, the utilities would get a new market for their product. PHEVs would increase residential consumption of electricity by about 30 - 40 percent. The increased generation could lead to replacing aging coal-fired plants sooner with newer, more environmentally friendly versions.

—Michael Kintner-Meyer

The potential for lowering greenhouse gases further is quite substantial because it is far less expensive to capture emissions at the smokestack than the tailpipe. Vehicles are one of the most intractable problems facing policymakers seeking to reduce greenhouse gas emissions.

—Rob Pratt, PNNL

Finally, the study looked at the economic impact on consumers. Since PHEVs are expected to cost about $6,000 to $10,000 more than existing vehicles mostly due to the cost of batteries, researchers evaluated how long it might take owners to break even on fuel costs.

Depending on the price of gas and the cost of electricity, estimates range from five to eight years—about the current lifespan of a battery. Pratt notes that utilities could offer a lower price per kilowatt hour on off-peak power, making PHEVs even more attractive to consumers.

Adding smart grid communications technology to ensure the vehicles only charge during off-peak periods and to provide immediate, remote disconnect of chargers in event of problems in the power grid would make them attractive to utilities.

The final copy of the study will be available via the Web in several weeks, according to PNNL.



This GCC article illustrates how an understanding of the subject contributes to superior reporting. The Wall Street Journal covered this story in 6 column-inches or so and not once mentioned the use of *off-peak* electricity. When I read that piece, I could not understand the results, given that producers like TXU claim impending production shortfalls. When all charging is done off-peak, problems meeting peak demand are irrelevant.


How about we use the off peak capacity to store energy such as producing hydrogen, charging salt water vat 'batteries', spinning up flywheel capacitors, etc? The hydrogen could be consumed later to suppliment generation at peak or sold off to other uses. There is a military base in the south I have heard of that uses tanks of salt water as large batteries for when there are power outages.

Just some ideas.....


_There is enough Li (12+ million tons global) for ~240 million PHEV. After which, you would have to go with other technology using other materials, i.e. carbon aerogel ultracapacitors.
_Converting all of these plants to combined cycle steam+gas turbine would boost efficiencies, at natural gas and coal fired plants. It would be easier to do at gas fired plants since many of them already run gas turbines.

Rafael Seidl

Jason -

your ideas may be relevant to electricity generated by unpredictable renewable sources, especially wind power. However, the article specifically excluded those as well as nuclear power from consideration. Besides, there are significant losses in each energy conversion step as well as in the transport of a given energy form to another location. This is especially true for the storage of electric power in just about any form. For economic efficiency and minimum ecological impact, you want to use the most direct possible conversion chain from the primary energy source to the where the rubber meets the road.

In other words, all those PHEVs would be charged at night using electricity generated from fossil fuels, primarily coal and natural gas. The electricity is stored only once. Coal has the advantage of being cheap per BTU but it generates a lot more CO2 per unit of electricity production than hydrocarbons, especially natural gas, do. The advantage therefore lies in the political and economic shift away from crude oil, which is heavily sourced from outside the US, to domestic coal.

If the scrubbed and cooled flue gases from a coal-fire power stations are used to produce starch or oil using intensive algaculture, the biofuels produced from this feedstock can help support the hydrocarbon demand from the ICEs. It's an expensive solution, but perhaps less so than the true sequestration of flue gases that many argue would otherwise be necessary to mitigate climate change.

Note that Australia, South Africa, China and others also have massive reserves of coal. Western Europe has more or less depleted what it had, while Japan never had much to begin with - they are more likely to switch from oil to natural gas from Russia, Algeria etc. than to coal. In addition, there are vast methane hydrate deposits under the continental shelves but the technology to extract it safely and economically does not exist yet.

Mridul Kashatria

How about changeable batteries for Cars and other vehicles. Similar to our mobile phones, imagine a car in which the battery can be changed whenever required.

Then cars could be sold to the customer without the battery (very less car cost), and the electric companies charge their amount for the batteries.

Power plants will supply charged batteries to all the petrol pumps and the user can just move in the pump station and replace batteries when required.

No need for the user to maintain or replace batteries. Vehicle costs could be brought down.

Handling batteries will be the task of Power plants, they'll upgrade their batteries with newer technology.

In short, take the battery burden off users and put it on somebody who can manage the system well.

What do ya say?

--Just a Whacky Idea!


It would be nice to have 50% of all cars be plug-in electric and 50% of all electricity generated from wind & solar energy.

What would OPEC do then with their $5/barrel oil?

Kenny Beaucht

Anyone expecting 50% electricity from wind and solar
should get in touch with the reality of electrical
power generation in this country. Wind is the last technology I would spend money on to reduce demad/increase green supply. Geoexchange subsidies I estimate to be not only 8 times more effective than wind in terms of sheer beneficial energy results, but also continues to enrich the homeowner and society by reducing the total cost of energy. Wind does exactly the opposite. Wind also has the very nasty habit of being nonexistent when demand peaks. This means that any wind capacity added to a utility's grid cannot be used to establish its peak demand capacity. In other words, when it's hot and electrical demand peaks, wind cannot be found, and the utility can add all the wind it desires, but still must maintain, staff, and have ready all those controllable, fossil fueled plants. You can never replace any of them because of added wind power. That
makes any calculations of the price of wind tricky.
When calculated realistically, wind power is very expensive for any systems that see year over year growth and don't already possess lots of excess capacity, such as is the case for virtually every single utility in the country. In terms of how much effect there has been from 2 years of the most massive construction of wind turbines, the anser is that it is imperceptible. Total
electrical capacity in the U.S. is close to 1,080,000 megawatts. Wind turbines possess plate capacities of 10,000 megawatts, but, unlike other power plants, which
easily produce 95% and up of their rated capacity, wind
real output generally runs around 25 to 30% of capacity,
making total U.S. wind power output aroud 2500 megawayy, or less than one quarter of one percent of the U.S.
total. Last year wind power increased by 2500 megawatts plate capacity, or around 800 megawatts actual capacity.
The increased electricity demand from 2005 to 2006
was approximately 1 and 1/2 percent, or 16,000 megawatts
of new capacity. Therefore the total wind added during that time was less than 5% of just the increase in demand. I think it unlikely that there will ever
be a fossil fuel power plant shuttered because of the
addition of windpower. Even the mainstream media is
beginning to recognize the gigantic problems with wind power and the fraud of attempting to stampede this country into buying a bill of goods, just because there are those politicians who frantic to "do something" to get votes from a mostly hysterical public. Until wind technology acquires the ability to produce its power when and where its needed, wind is a flop as a viable
energy source.


Rafael, what about the capacity of V2G? I've read that a reasonable fleet of PHEVs or BEVs could store a rather large amount of power, perhaps enough to even enable us to use wind and solar to a much higher degree than the usual 20% max of total estimate.

tom deplume

In the US taxes on gasoline and diesel fuel provide the revenue for road construction and repair. If most vehicles are plug-ins how will the lost revenue be replaced. Placing electric meters in the cars which could be read digitally through the grid may be one way to do it. My WAG is that a tax of as much as 10 cents/kwh may be needed. One of the factors being tauted to offset the higher cost of plug-ins is the relative low cost of electricity and the avoidance road fuel taxes.


I don't have any background with the cost of operating a power utility, but nevertheless I'll take a simple stab at estimating the cost reduction if power plants were utilized during off peak hours.

Assume their current cost of operation is split between labor (payroll/management/general) and capital (facilities/equipment/etc.). If the labor portion is 1/3 of their operating costs and the capital is 2/3 thirds, then you can estimate the cost savings if we had better utilization of the equipment/facilities.

operating cost = Labor + capital
labor = 1/3 operating cost
capital = 2/3 operating cost

With better utilization of the equipment (i.e., using the equipment during the off peak hours) then your total labor cost would increase from 16 hours/day to 24 hours/day (50% increase), but you capital investment would be roughly the same (maintenance goes up, but let's ignore that for now).

new operating costs = 1.5 labor + captial
= 1.5 (1/3 operating cost) + 2/3 operating cost
= 7/6 operating cost

So the cost for operating around the clock goes up 16% over the current cost of operating a utility.

Now, let's look at the cost per kw-h of electrical power. The power price is determined as operating cost divided by the total power output.

cost (cents/kw-h) = operating cost/output

In the scenario where we operate around the clock, we can figure out how much we should expect to pay based on our current costs. Let's assume output increases by 50% (i.e., the power plant operates 24 hours/day instead of 16 hours/day) - (new power output= 1.5*output).

New cost= new operating cost/new power output
= 7/6 operating cost / 1.5 output
= 7/6/1.5 * operating cost/output
= 7/9 cost

So, with all of these assumptions, you'd pay seven ninths what you're currently paying per kw-h for electrical power. You can see why the utilities are really interested in PHEVs. They've already made the investment, the infrastructure is in place, and they can split the savings with the consumer and still invest where needed to better handle peak production issues.


Institute toll roads for highways, bridges, etc.


Tom: You can more than offset the tax revenue losses by bringing your troops home from Iraq. You also need to do something about your horrific balance of trade.

Marcus: While I think V2G is an elegant idea, I wouldn't be in a hurry to let them use up precious cycles in my battery.

Why does something in the back of my mind tells me that this report is just a little optimistic. Seems too good to be true.


Neil, if trust was the only issue then I don't see a problem. After all, the utility would be paying you for that electricity and once a few brave people demonstrate that its reliable then the more timid may follow!


Marcus: Have you seen any studies that discuss the economics of V2G? I'm wondering if the amount they can pay me to store energy in my limited deep discharge battery will cover the premature cost of replacement. I'd do it if it was cost neutral to me and didn't cause me any problems.


Nevermind the ramifications, if we pull out of Iraq, they will likely either go to Afghanistan, to bases around the Middle East, or home bases. It would also mean a massive movement of equipment. Worn down gear, vehicles, and other systems would have to be refurbished/rebuilt. Current shortages in war materiel must be rectified. Units short on men and gear must be brought up to strength. Combat and reconstruction ops in Afghanistan will become more intensive. All of this will be expensive.
_Tens/hundreds of billions of Dollars/Euros, and hundreds of thousands of soldiers are needed. The Afghan govt, Army, and police need to be beefed/developed/cleaned up, to the point of being able to lead the effort. It could be another 5 years before the US/NATO will be able to pull out of the country in significant numbers. Another 10-15 years of international assistance (economic, governmental, military, etc.) will be necessary. Eventually, there might be a need for a pernament presence in the form of enlarged foreign military/govt. attaches, for training and mentoring (NCO/CO/General/governance/economic/etc).

_Afghanistan was never going to be cheap. With a generation of war and destruction, years of drought, and drug problems, the costs will be a shock to many.


Cont. from above:
High speed electronic/optical/etc. tolls-up to 100mph and equip with signs and cameras-may be a way to do this. Congestion pricing and toll/HOV lanes could another aspect of the system. The system would pay for itself, through tolls and speeding tickets, and road maintenance (possibly state/highway police too).


One reason fuel economy is lower than Govt. numbers is because of speeding. If you go 75 instead of 55, you incur a increase in total aerodynamic drag of ~85%. Traveling 85 instead of 60 will double your total aero drag.


Neil, I have to admit I haven't read deeply on this issue however I am fairly certain that the utility savings means that they would reimburse you above break-even, including battery deterioration although I suppose it will always depend on the battery. Here is a good list of peer-reviewed papers on the subject.



Electric motors also tend to more efficiently at lower RPM, thus lower speeds...or use transmissions w/gearing ratios that allow for peak efficiencies.


Neal, this article summary has a table of theoretical profits to the vehicle owner which includes loss due to battery degradation. For a city type BEV acting as a spinning reserve the owner may gain $311 per year. For a full Tesla type vehicle the annual profit may be around $720.


Jim Bauman

When I read the results of this DOE study on PHEV
and grid demand, I was reminded of some calculations
I made last week on the question of electrical
demands posed by an all electric fleet of personal
transportation highway vehicles.

Here were my assumptions and results:
1) I know for a fact that the U.S. consumed 120
billion gallons of gasoline last year, mostly
for highway vehicles. I reduced this figure by
10 billion to account for boats, lawns mowers,
motorcycles, etc.
2) I happen to know that, in highway driving, one
gallon of gasoline is equivalent to approximately
6.2 kilowatt hours of electricity, in terms of
its ability to propel the car agiven distance.
3) The above calcs yield a value of 7.9% of U.S.
electrical generating capacity (1 million
megawatts) would be required to power all
gasoline vehicles if they were electric and
only drove on the highway. Since not all driving
is highway mileage, and since electric cars'
mileage is not reduced during city driving, the
actual percentage of capacity required is
obviously less than 7.9%.
I'm estimating that it would be around 5%.

The problems I have with the DOE study is that it
doesn't specify the assumptions that were used or in any
manner explain its calculations. Consequently, I have no
way of evaluating the reasonableness of its conclusions.
Even assuming all PHEV have a range of 33 miles, just
knowing that average daily mileage is 33 and that there
are 220 million vehicles does not allow the calculation
of the total electric miles driven by the fleet. One
has to know the distribution of vehicles by their daily
mileages in order to make the calculation.
Another strange quirk is that the study apparently is
assuming that 100% of the nation's cars could be PHEVs.
But that's totally impossible, since nowhere near 100%
of drivers have a place to plug in their vehicle at night. People who live in condos, apartments, or townhouses, and those without a garage or carport would not pay for PHEVs. So when the study claims that 84% of PHEVs could be recharged using excess capacity, I would characterize that as misleading or, at the least, confusing.
Another issue is that I consider it highly unlikely
that the nation would go completely (or, as completely as possible) with PHEVs before a practical electric car
appears on the market. An electric car fleet changes
everything, since it constitutes a greater demand on the
grid (since everyone could own one of these cars, and all of the car's mileage would be electric) and a demand that would be distributed more evenly thruout the day (since a practical electric car means a car that can be recharged quickly, thus rechargeable at public stations). However,demand would still be concentrated at night, especially if nightime electric rates prevail.

Jim Bauman
Arlington, VA


You end up with a better load profile for more efficient combined cycle plants. The investors can pay back larger plants sooner with 24/7 revenue. This would mean more combined cycle and fewer peaker plants in densely populated areas. The future of our power grid may need some investment however...

Bill Young

I am not much of a conspiracy theorist, but there is an interesting article on electrifyingtimes.com that hypothesizes that Panasonic is prohibited by patent liscense lawsuits from making larger NMHydride batteries suitable for PHEV and BEV vehicles and that they are constrained for another 9 years.

The article suggests that is why Panasonic refuses to make replacement batteries for the electric RAV-4s in California. It further suggests that Panasonic is under a confidentiality agreement on the liscense.

Many folks think that Li+ batteries are not ready for prime time and that NMhydride is the best current technology. This constraint in the NMhydride batteries could be a show stopper or at least a serious bump in the road for projects like this if it is true.


Bill I have heard this many times and I suspect its true. After all, Chevron now owns the patent. However I think Li+ batteries are now even better than NMhydride so I don't really see that there should be that much further delay. However things could have moved along a lot faster otherwise. I am no patent lawyer but I thought there were some rules for making use of patents or loosing them. I guess somehow that doesn't apply in this case.

Dave Calloway

Another reason utilities like the idea of PHEVs is that they can be used to SUPPLEMENT capacity during peak demand. PHEVs are primarily charged at night during off-peak hours, but a large number will remain on the grid during the day. During peak demand, power can be drawn FROM the PHEV batteries to supplement the grid, preventing brown-outs, and reducing the need to bring expensive peaking power on-line. This capability can be added in conjunction with the current controls some utilities use to turn off air conditioners and water heaters during peak load. The difference is that rather than simply cutting off power, the PHEV batteries can actually supply power during these peak load times and then be re-charged during the off-peak times. A sufficient number of PHEVs in their service area can eliminate the need to expend capital to construct peaking generators that would only be used a few times a year, saving the utilities a great deal of money.

Google did a study recently and found that they might actually save money by buying PHEVs for their employees and using the PHEV batteries to limit their own need for peak power. It turns out that Google's big electric bill is driven in large part by their peak demand, not their average demand. By shaving power use during the peak periods, they would save nearly enough money to buy the PHEVs, while at the same time making a strong evironmental statement and providing a nice benefit to their employees.

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