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Study Suggests Planning for Grid-Based Light-Duty Vehicles (PHEVs or EVs) Should Factor in Impacts on Regional Water Resources

A study by researchers at the University of Texas at Austin has concluded that converting light-duty transportation from full gasoline power to electric power by using either plug-in hybrid electric vehicles (PHEVs) or battery electric vehicles (EVs) is likely to increase demand for water resources—primarily due to increased water cooling of thermoelectric power plants to accommodate increased electricity generation. The study assumes continuation of the current electricity generation mix, for methodological ease, even while recognizing that “changes will happen.”

The potential increase in usage, assuming wide-spread adoption of PHEVs and EVs, represents a significant potential impact on regional water resources and should be considered when planning for a plugged-in automotive economy, according to the study by Carey King and Michael Webber, published online in the journal Environmental Science and Technology.

The authors of the study, which has already been sensationalized with headlines such as “Plug-in Cars Could Drain US Water Supply”, are careful to point out that they are not saying that the negative impacts on water resources make the shift to grid-based transportation undesirable, but rather that such impacts should be quantified ahead of time to avoid unnecessary conflicts. The study concludes with the suggestion of several steps and policies that can be promoted to enable sufficient water access for enhancing PHEV market success.

King and Webber calculated that in displacing gasoline miles with electric miles, approximately 3 times more water is consumed (0.32 versus 0.07–0.14 gallons/mile) and more than 17 times more water is withdrawn (10.6 versus 0.6 gallons/mile) primarily due to the increased cooling needs.

Water consumption describes water that is taken from a concentrated source and not directly returned—e.g., a closed-loop cooling system for thermoelectric steam power generation where the withdrawn water is run through a cooling tower and evaporated instead of being returned to the source. Water withdrawal describes water that is taken from a concentrated source, used in a process, given back from whence it came, and available again for the same or other purposes—e.g., an open-loop cooling system for thermoelectric steam power generation that withdraws cool water from a reservoir into its condensing unit and discharges that heated water back into the reservoir.

The typical US driver would drive 4,500, 7,100, and 8,600 electric miles per year in a PHEV20, PHEV40, and PHEV60, respectively. For example, it takes 114, 72, and 59 million PHEV20, PHEV40, and PHEV60, respectively, to drive 500 billion electric miles annually. [Total miles driven in 2003=2.66 trillion] Since there are 234 million gasoline LDVs on the road today, displacing one-sixth to one-fifth of gasoline miles with 114 million PHEV20s, or 49% of the vehicle fleet, sounds feasible, but with annual sales rates of cars and light trucks/SUVs amounting to 17 million vehicles per year, it would take 7 years if every vehicle sold were a PHEV20. Comparing the displacing of the same 500 billion gasoline miles with electric miles of PHEV60s requires replacement of 25% of cars, light trucks, and SUVs, for which the tradeoff would be annual water consumption of 160 Bgal/yr compared to 35–70 Bgal/yr using gasoline. Also, 5,300 Bgal/yr would be withdrawn instead of 300 Bgal/yr. These increases in water usage represent approximately 0.2–0.3% and 3%, respectively, of overall US water consumption (100,000 Mgal/d freshwater in 1995) and withdrawal (408,000 Mgal/d in 2000).

...Water rights and access are also largely a regional issue due to varying laws, rain patterns, river paths, and groundwater supply. Thus, in order to implement the electron automotive economy where a substantial number of miles are driven electrically, the water demands need to be assessed on a regional basis. This means that some relatively wet regions of the United States may be able to support more PHEVs at lower cost than other relatively dry regions. Also, dry regions can focus on cooling techniques that require little water or electricity generation technologies, such as wind and photovoltaic solar that do not consume and withdraw water. Most importantly, public policy decisions that promote PHEVs or electric vehicles need to consider the impact on water resources beforehand because the increased demand for water withdrawals is potentially quite substantial and could impact water availability or rights for irrigation, municipal, and other competing purposes.

The authors suggest four initial steps and policies:

  • Promote research and development of distributed generation and renewable energy sources that use little to no water and can possibly be located onsite where PHEVs are charged.

  • Develop regional water plans that consider increased demands for electricity for PHEVs in order to ensure adequate water access in light of competing water demands for municipal and irrigation uses.

  • Move to generate more electricity by methods that do not withdraw such large amounts of water.

  • Use reclaimed, saline, or other water sources that are suitable for thermoelectric cooling, but unsuitable or unable to be treated economically for drinking.




@ Mr.Kramer
I just read the Sciencenow article and it appears more unbalanced than most of the others I've read commenting on this "report".

John Taylor

This “study” needs nominated for an award as dumbest study done this year.,

First, the extra water used by electricity production needs to be offset by the water usage to drive cars on oil or ethanol, both of which use lots of water, and even the worst electricity generating systems show a net gain.

Second, water consumption will be a problem in the near future simply because there is a fixed water flow, and an expanding population using it on a per capita basis. The limits of the resource are near than you think. Electric cars, or not, the problem needs dealt with.

On a good note, at least the study does make a case for more environmentally responsible electric generation, and better water resource management. Unfortunately, it neglects noticing the oil refineries turning water into oil tailings sludge.

Stan Wellaway

"Study Suggests Planning for Grid-Based Light-Duty Vehicles (PHEVs or EVs) Should Factor in Impacts on Regional Water Resources"

That's what this thread began with.

Surely planning for EVERY type of industry should factor in impacts on water resources. The question is why does this report single out one particular industry as being in any greater need of attention than every other?

"Study Suggests Planning for Every Industry Should Factor in Impacts on Regional Water Resources"

So who briefed them to target just the one industry?


It seems like a natural to cool power plants and distill sea water at the same time. You see the stacks at the inland plants, but seashore plants just pump the warm water back out to sea.


sjc: It won't be any easier to use seashore salt water for cooling. Environmentalists will prove that any heat added to the ocean will destroy something important; probably life on Earth.

Whether they are right I must leave to the judges. I can't know.

I generally favor nuclear but want serious analysis and review before licensing. But why must that take years or decades?


They already use sea water to cool nuclear power plants at San Onofre and Diablo Canyon on the Pacific Coast. The warm water had been going out to sea for decades.

The one reason that I can see not to is the incredibly low price of water for farming. An acre foot is about 300,000 gallons and that goes for around $100. 1/3000th of a cent per gallon is not incentive to distill any sea water for farming and farming takes 85% of the water in California.

"They already use sea water to cool nuclear power plants at San Onofre and Diablo Canyon on the Pacific Coast. The warm water had been going out to sea for decades"

That is exactly my point. Even after decades of sucessful experience it gets no easier to build anything nuclear. And generally harder. I used to live near San Onofre and there was a tremendous fight about using sea water for cooling. I expect the same delays on every occasion.

The last time I checked there were 23 or 29 plants - I forget which - waiting for licences. And not one was expected to operate by 2015.


So, instead of putting warm sea water out, just distill sea water to fresh water in a closed loop. You might need final cooling towers, but that is not a big thing. It comes down to economics and the cheapest way to do something maximizes surprise there.

Bob Bastard

Could the warm sea water be piped and used for HVAC in the cases where the plant is located reasonably close to an urban area?


State of nuclear reactor licenses as of Dec.2007 based on actual filings.

My guess. There may be 24 intentions but the number actually going to be built will be way smaller. The nuclear 2010 program only gives a tax break to the first 6 reactors to go online. This is what's mainly created this recent wave of interest/demand. I expect increased interest as the present fleet of reactors gets nearer to their operational lifetimes but there is no reason they could not renew their operational licenses like they did this time. We will have to see if the expense of upgrading will be worth it. Also utilitites are loath to be the first to spend a couple of billion dollars on new construction.


The difference between "closed" and "open" cooling systems isn't what some posters here think it is.  A "closed" system recirculates water, but that doesn't mean it has no evaporative losses (think cooling towers here).  Only a "dry" cooling system will eliminate evaporation.


I finally came to the conclusion that farm water is too cheap to compete with desalinization of water by thermal distillation. At 100 dollars per acre foot, the farmers are so used to cheap water that they would not even think of paying more, unless they had to.

Harvey D


I didn't mean to offend Texans. It is a joke around here that every thing from Texas must be exagerated.

We are 96% Hydro, 2% Nuclear and 2% Wind (going to 5%+ within 5 years). In our case, 100% PHEVs-BEVs and electrified HVAC would not create much more heat & pollution but probably much less than the existing refineries, 4+ million ICE vehicles and oil-gas-wood HVAC.

Pro oil-ICE people will use worse case to try to prove their point.

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