What do you think when the topic of electric cars comes up? Not in my lifetime?  Green dreaming?  Birkenstock babble?  A cover page topic for the next issue of Popular Mechanics (the same publication that brought us the nuclear powered airplane)?

For me, it’s where are we going to get the power to charge up 125 million cars? That’s the current average number of cars on the road in the U.S. I’m leaving trucks and buses out of the picture for now.

Seriously, what would happen if we woke up tomorrow and 100% of all our cars were 100% battery driven electric? Could the U.S. electrical grid handle this additional load? I decided to figure this out. Here’s what I came up with.

The numbers get big. With those 125,000,000 cars we collectively pump in 131,400,000,000 gallons per year of gasoline (that’s 131.4 billion…with a “b”). With an average fleet mileage of 24 mpg, we drive 3,153,600,000,000 miles each year (that’s 3.153 trillion with a “t”).

How Much Power Is Needed? After some energy unit conversions all that gasoline represents the equivalent of 4.8 billion megawatt-hours (“mwh”) of energy consumed annually. Unfortunately, only about 17% of that energy actually goes into moving the cars while the rest is lost to friction and the inherent inefficiencies of the internal combustion engine. By comparison, approximately 80% of electrical energy delivered by the grid gets productively used in an electric motor driven car. Accounting for these efficiency differentials, the U.S. would have to deliver 1,022,219,055 mwh of additional electrical energy each year to move those 125,000,000 cars the same distance as with gasoline.

A trillion megawatt-hours of electrical energy a year!  A big number again but how does it compare to how much we already consume annually?  Turns out we consume about 4.2 trillion mwh a year so with all those cars plugging in we’d consume an additional trillion mwh or roughly 25% more. Is that a lot? Can we do that?

We Have Enough Power. The U.S. has approximately 1 million megawatts of installed power generating capacity. If all those plants ran at full output 24 hours a day 365 days a year we’d say that the U.S. power plant feet ran at a 100% capacity factor. But it doesn’t. It runs at roughly a 44% annual capacity factor. There are many reasons for this but the simpler explanation is some plants are resource constrained (wind-30%, solar-15% etc.), some run maxed out at 90% or more (lowest cost nuclear) and the majority run somewhere in between (coal – 75%) depending on market demand and pricing.

To generate the 1 trillion additional mwh needed for our new 100% electric car fleet, the power plant fleet would have to increase production from a 44% capacity factor to 54%.

In my estimation, this is not a stretch and is well within the technical limitations of the existing electrical system. Some plants would simply have to run more of the time, especially plants that run on natural gas. This would eat substantially into our existing reserve margin, but unlike my scenario, all cars wouldn’t go electric overnight so there would be ample time to build any additional generating plants needed.

Are Electric Cars Worth It? If we have sufficient power to go with electric cars, why haven’t we yet?

To date, electric cars have either been too expensive or incapable of going very far (or fast) before needing another charge. In short, impractical and uneconomical.  That may be changing and changing fast. The race to come out with a truly affordable electric car is on and it’s hot and getting hotter. Eighteen months ago there were already 30 different electric car companies burning up investor dollars in search of this battery operated holy grail.

One example is the Norwegian company Think with its small 100% electric car reminiscent of the SmartCar. More recently backed by keen investors like Kleiner Perkins and Rockport Capital, in March, 2009 Think announced plans to open a U.S. factory. Even more interesting is the 112 mile range, 62 mph max speed and a targeted price tag of $15-17k. Not your best choice for a cross country road trip, it’s clearly aimed at the urban/suburban driver, hence the “Think City” model name.

The great thing about electric cars is that the variable operating cost per mile is substantially lower than with gasoline.  With gas at $2.50/gallon you can figure around $0.10/mile for a conventional car. With retail power at $0.10/kwh, the Think would run you around $0.03/mile – or 70% less!  And if (when!) gas gets back up to $5.00/gallon the variable “fuel” cost to drive an electric car would be 85% less than with gasoline.

The 10 year present value of the fuel cost differential between $5.00/gallon gas and $0.10/kwh electricity adds up to almost $30,000 assuming an 8% discount rate (yes, I’m ignoring other fixed/variable costs for now thank you very much). I think that’s enough to make a lot of people think seriously about the Think.  Sure, it has zero emissions (ignoring those from the power plant – which could be zero too with solar, wind etc.), but just like the Toyota Prius,  price and value will win the day – the kind of green that you find in your wallet – not the environment.