Gasoline, electricity, and the energy to move transportation systems

By David Herron

Solar power systems can produce power anywhere, like your rooftop, and produce more power per acre than corn-based ethanol production.  It's possible, with solar power, for a home-owner to generate enough power on their roof to power their home and an electric car.

In our 100+ years experience as a society with gasoline driven cars, one behavior baked into society norms is going to the gas station. Regular as clockwork we have to stop every 300 miles or so, at a gas station, spending a few moments pumping carcinogenic fluids into our cars to keep them going. Fueling your car at home is a strange new thing, but it's a daily occurrence for electric car drivers.

But the big challenge to conventional norms is that an electric car owner can create their own fuel, at home, on their roof.

The gasoline car owner simply can't do the same, without investing in the land to grow a big corn crop from which to make ethanol. The electric car owner who owns their own home, and whose home is suitable for solar energy (south facing roof with an unobstructed view of the sky) can easily put up solar panels and generate enough electricity every day to power their home and their car.

See also: Understand home solar power system design with this detailed walk-through to understand how solar power is implemented.

Powering a car with Corn Ethanol

At the risk of an unnecessary detour, this ( article goes over how much corn and land is required to create ethanol to power a car. A typical ethanol car gets 8.5 kilomoters per liter, and it takes 3.13 kilograms of corn to produce a liter of ethanol. Average Americans drive 15,000 miles a year, or about 24,150 kilometers a year.

  • fuel required: 24,150 km / 8.5km/liter = 2841 liters of ethanol a year
  • corn required: 2841 liters * 3.13 kg/liter = 8892.88 kg of corn per year per car
  • land required: 8892.88 kg / 3,225 kg/acre = 2.75 acres of land growing corn per year per car

The corn doesn't magically make itself into ethanol. The fermentation process requires vats and grinding machines to process the corn, farm equipment to tend your field, and a lot of time to ensure the crop yield is up to snuff. These machines require money, and chemicals, and seed, and fuel, and labor.

What about scaling this up to the 135 million passenger cars cars in the US? ( ( in 2006 according to the Dept of Transportation) Powering them all on corn ethanol requires 371 million acres of corn production, plus the industrial infrastructure to process all that corn into fuel. And, isn't corn supposed to be a food crop? What are we doing diverting food into fuel? According to the US Census Bureau, in 2010 there were 920 million acres of farmland, so enough ethanol production to power all US passenger cars would take over 1/3rd the total current farmland.

That land requirement, 371 million acres, is almost the size of Texas, Alaska and California combined. (those three add up to 421 million acres) That's about 10 Iowa's or about 8 Nebraska's.

Are you getting the idea that corn ethanol is a bad solution to producing fuel for cars?

Powering a car from solar panels

Now let's do a similar estimation for electric cars, starting with how much of a solar array is required to power a home and one car.

According to the ( U.S. Energy Information Administration, the average "residential utility customer" in the U.S. consumes 10,837 kWh a year or 903 kilowatthours (kWh) per month. That's 30 kiloWatt-hours of electricity per day. Being an average some will consume more, others less.

According to an online calculator to estimate solar array size requirements, 100% coverage of 10,837 kWh/year requires an 8.42 kiloWatt solar array in an area (Columbia Missouri) with 4.75 hours of usable sunshine a day. In an area like Phoenix Arizona, with 6.58 hours of usable sunshine a day, the solar array required shrinks to 6.08 kiloWatts. The key is the amount of usable sunshine a day.

That's for the household, what about the car? For the average 15,000 miles per year of driving, and 300 Wh/mile, the average electric car should consume 4,500 kiloWatt-hours per year. Per electric car. A household with one electric car would then see its average electricity consumption rise to 15,337 kWh/year. Again, these are averages calculated on the back of a napkin, so don't put too much credence into the accuracy. Some will consume more, some less.

Going back to the solar array estimating calculator, the size required in Columbia MO is now 11 kiloWatts or so. That will cover one household with one electric car.

According to a slide deck by the ( Dept of Energy published in 2009, the average size of a home solar array is 3-5,000 kiloWatts.

A do-it-yourself 11 kiloWatt solar array from ( costs $18,200, and consists of 40 solar panels along with racks and wiring and inverters. The roof space required is 750 square feet.  Another similarly sized system from the same place, costing $19,000, has 35 panels, but still requires 750 square feet of roof space.

Therefore it's feasible for the average U.S. home to produce enough electricity, on their roof, to power the home and one electric car. This wasn't even a fair comparison, because for solar we considered more (house plus car) than we did with ethanol (only the car).

It's easy to conceive scaling this up to every home in the U.S. No land space has to be diverted from its existing use, since the land is already taken up by homes and businesses and parking lots.


The connection between wind power, solar power, and electric cars is strong. So strong that often-times promotional shots of an EV show solar panels or wind turbines in the background.

It's so compelling that many electric car owners go ahead and put solar panels on their roof.

As we've just seen it would be feasible to supply a large portion of our collective electricity needs with solar panels on rooftops and over parking lots around the country. As we saw elsewhere, electricity from wind or solar power systems is a zillion times cleaner than any fossil fuel power plant possible.

What's holding us back? We know in our hearts it's the right thing to do, let's do it already.

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