Gas canThe Do the Math blog series has built the case that physical growth cannot continue indefinitely; that fossil fuel availability will commence a decline this century—starting with petroleum; that alternative energy schemes constitute imperfect substitutes for fossil fuels; and has concluded that a very smart strategy for us to adopt is to slow down while we sort out the biggest transition humans have ever faced. The idea is to relieve pressure on the system, avoid the Energy Trap, and give ourselves the best possible chance for a successful transformation to a stable future. Since building this case, I have described substantial adaptations in our home energy use, but have not yet addressed the one that bears most directly on the immediate problem: transportation and liquid fuels. Let’s take a look at what can be done here.

What are Our Goals?

Yearly production of conventional liquid fuels may decline at rates of 2–5% once the decline starts. Artificial (geopolitical) factors may steepen the decline. But even at a modest 3% per year decline, we will be down to half the annually available fuel in a two-decade timeframe. Substantial energy transitions of the past have taken much longer to accomplish, so dreams of shiny replacements—like a fleet of electric vehicles for everyone—need to be tempered with some sense of historically demonstrated reality. Indeed, Chevrolet has scaled back their production of the Volt due to flagging demand. Is it because oil prices are low? Are gasoline prices too low to send the right signal? No! Oil prices have hovered at or above $100/bbl for over a year now. Gasoline prices are in the red. And Chevy ramps down production of arguably the most impressive plug-in hybrid vehicle on the market.

Chevy VoltChevy Volt

I understand this from a personal perspective. Our car is starting to groan with problems, costing $500 every six months or so to keep it running smoothly. I started entertaining the thought of moving on. Given my trepidation over oil stability, my love of efficiency, my personal experience building a solar PV/battery system, and my enjoyment of smart technology, I was attracted to an inherently efficient electric car that I could charge independently from my very own power station. Yet the occasional longer trip is well provisioned by an on-board gasoline engine. So plug-in hybrids seem like the right solution for me. I don’t want to get stranded with a dead battery in an electric-only car, which I perceive to be only a matter of time given the unpredictability of life: things come up. Few plug-ins are available, and the purist in me wants a car that can be 100% electric except for long trips. The Volt brilliantly matches my parameters. Then there’s the price. Realistically, I’d be looking at $40–$45k. Sure, there is a $7k government tax break (some fraction of which I might qualify to receive). Still, I can sustain the maintenance costs of our current car for some time and still be ahead financially. Also, the embodied energy of a new purchase erects another barrier.

The point is, I backed away from my drooling attraction to the Volt because I judged it to be an extravagant expenditure. Even my most clever arguments could not rationalize it. And even though I cringe to think of myself this way, objectively speaking my wife and I are in the upper quintile (20%) of household income in the U.S. That makes me upper class. Blech. I’ve never tried caviar, but doubt I would like it—and I don’t drink, so champagne is lost on me. I’ll sooner take a bean-rice-cheese burrito than a fancy dinner. But there we have it: I’m in the upper class. And even I shied away from the expense of a very attractive plug-in hybrid car. So I am not too surprised to hear that Chevrolet is ramping down its production. Yet I’m disappointed all the same. My take-away is that transition to a different transportation fleet is easier dreamed than done. It’s expensive. Economic difficulties imposed by high fuel costs result in recessionary pressures, leaving even fewer in a position to afford an extravagance like a shiny electric/hybrid car.

Again, I come to the conclusion that one thing we can do—totally under our own control—is to reduce our demand of liquid fuels faster than the naturally-imposed decline rate. And again, I look for factor-of-two level solutions, rather than piddly few-percent window-dressing. Let’s kick this problem in the teeth!

Comparing Scales

According to the U.S. Energy Information Agency (EIA), in 2001, 107 million households drove 191 million vehicles an average of 12,000 miles each (19,400 km), consuming a household average of 1057 gallons (an even 4,000 liters) per year.

By comparison, my household has two cars: a sedan getting something like 30 MPG (7.8 l/100-km), and a pick-up truck at about 20 MPG (11.8 l/100-km). Wait a minute! This Do the Math guy talks up energy efficiency, but drives a pick-up truck with terrible gas mileage? The nerve!

Call it my Southern heritage: I’ve always driven a truck (has room for my telescope, for one thing). But to assuage my guilt, I have been tempted to make a bumper sticker that says: this truck uses less gas than the average Prius. “By what technology?” people might ask. “A flux-capacitor, perhaps?” No, it’s very simple. It mostly sits parked. I ride the bus to work, and choose the car for around-town trips that do not require the attributes of a truck. We filled the tank a few weeks ago (in March) for the first time since November. In the three consecutive calendar years from 2008–2010, we filled the tank eight times (124 gal; 469 l) while driving 2300 mi (3700 km). That’s fewer than three tanks per year! Then we took it to Seattle with lots of stuff—and cats—for a three-month stay. Now it’s back to mostly sitting—when not being used by me or friends to haul stuff around.

For the car, we average 285 gallons per year (covering the span 2008.0–2012.3). My wife’s Pasadena-based job allows her to work at home, and very rarely travel to see her employers. Since 2008, we have put 1193 gallons into the car and 490 gallons into the truck, averaging 400 gallons per year: 38% of the national household average. This includes round trips from San Diego to Boston in the car, and to Seattle for the truck. If we remove these atypical jaunts (but keep the travel during our stay in these places), we’re down to 30% as much gasoline as the average American household. Even so, since each gallon of gasoline contains 36.6 kWh of energy, our gas habit for personal vehicles consumes 32 kWh/day, which far exceeds our natural gas consumption of 5 kWh/day and our utility electricity usage of 2 kWh/day (requiring about 6 kWh/day of thermal generation at the power plant). The numbers will be far more gasoline-lopsided for daily car-commuters who otherwise trim energy use at home.

The lesson is that reducing one’s use of gasoline is not only addressing the immediate threat of liquid fuels shortage, but it also tends to be one of the more significant sectors of household energy use, and is therefore ripe for reduction.

Obviously a couple in San Diego can get by with less gasoline usage than suburban or rural families can. And a New York City household can do just fine with no car at all. But even among our cohort in San Diego, our driving habits/dependencies require substantially less gasoline than standard practices. And this is the comfort zone for me: a factor of two reduction provides enough breathing room for me to feel that widespread uptake at this level can deliver the game-changer we need to evade the chaos and pain that a supply shortfall will bring. Coupled with an aggressive strategy to build a truly energy-resilient future, such voluntary reduction may be just the ticket for us.


Okay, let’s say you buy into the notion that we should personally strive to reduce fuel consumption by something approaching a factor of two. But you sense that it’s easier said than done. True. If it were easy, you would have been there already. After all, paying high prices at the pump is not something you do for fun. Here are some suggestions that we try to implement, and that may work for others as well.

Consolidate Errands: Adopt the mindset that it is highly undesirable to make a trip from home for a single purpose. If you just need milk, either do without until another excursion presents itself, or look ahead to future needs that you can also satisfy on the same trip, avoiding a separate trip later. If your excursion occupancy average (number of stops per outing) goes from 1.5 to 3, then you may have achieved a factor of two in fuel savings for errands. Naturally, most people already practice such efficiencies when possible. The difference can be in how disciplined you are about denying yourself “wasteful” trips. Sometimes I hop on the bike if I forgot the butter like an idiot, and can’t justify another gas outing (but want that butter!).

MTS busPublic Transportation: I never considered the bus to be an “acceptable” form of transportation until I lived in Seattle for three years and found that the bus service was actually quite good and convenient. I carried this attitude with me to San Diego, and moved into a house near a bus route to UCSD. The bus is my mobile office free of interruption, and I value that time each day. Many Do the Math words are generated on the bus, in fact. On my last trip to my hometown of Chattanooga, I rode the bus for the first time ever. I found it to be a tremendously convenient way to get downtown to meet a friend one day and my sister the next, without worrying about parking, etc. It felt like I had made a pioneering discovery—even though the bus has always been right there in plain sight. Buses work, and the service gets even better the greater the ridership.

Carpool: Another unoriginal suggestion, in plain sight. Even finding one person to share a ride immediately provides that magic factor of two savings. Coordination can be a slight inconvenience. But the benefit may far outweigh the cost. This is another place where an attitude shift can make all the difference. If you begin to view single-occupancy as an unacceptable standard practice, the burden of arranging shared rides may seem worthwhile. Social media is making it far easier to find and arrange rides. I wonder how many Egyptians protesting in Tahrir Square used the same social media that was so instrumental in organizing the protest to also arrange shared rides to Cairo or to the Square.

Full-Cost Accounting

It’s easy enough to say “hop on a bus and avoid putting gas in your tank.” But gas has to go in the bus’ tank. And each rider needs to claim a share of that expenditure. I don’t buy the argument that “the airplane is going there anyway, so the fuel is spent whether or not I occupy a seat.” This kind of marginal thinking is correct to a point, but also tends to be a barrier to change. It also kills democracy: “the candidate will be elected whether I vote or not, since the polling margin is 10 points in her favor.” Gee. If everyone came to that same conclusion, democracy would self-destruct. Passenger airplanes don’t travel between cities if no one is (or too few are) signed up to ride. Demand creates the service. It’s a cop-out to think that your choices carry no consequences. Remember that you are one of an aggregate, and aggregate demand creates massive impact.

In the case of my own bus commute, how much do I really save? Well, all of the buses serving my route are powered by natural gas. The voluminous storage tanks are a more natural fit for large vehicles than for passenger cars, so this is a nice way to reduce dependency on liquid fuels. I am getting (practically) infinite miles per liquid-fuel gallon on my daily commute! A minority of buses in San Diego’s fleet are the diesel versions are the New Flyer D40LF model, getting something like 3.2 miles per gallon. Statistics provided by San Diego’s Metropolitan Transit Services (MTS) indicate an actual performance of 2.8 in-service miles provided per gallon of diesel purchased for all MTS operations. We’ll say 3.0 MPG to make the math simpler. The bus seats about 40, and for much of my route during commuting hours, the bus has passengers standing in the aisles. At 40 people, an individual passenger is in effect getting about 120 MPG (2.0 l/100-km). But the bus is not always full, and for the route to exist, it must also provide service at non-peak times of day, and on weekends. According to MTS statistics, the route I utilize achieves an average occupancy of 11, so that the net passenger fuel economy would be about 30 MPG if my bus used diesel rather than natural gas. This is better than if I drove my truck (or the average American vehicle, sad to say), but it’s not astoundingly good.

Looking at the whole MTS fleet for fiscal-year 2011, 179 million passenger-miles were provided (3.7 miles is typical passenger ride length), and in doing so MTS purchased 7.3 million Therms of natural gas energy, 823,234 gallons of diesel, and 377,890 gallons of gasoline. It takes 1.25 Therms for a gasoline-gallon-equivalent, so 83% of the transportation energy came from natural gas. In terms of liquid fuels use, the fleet achieved 150 passenger-miles per gallon of liquid fuel, meaning each passenger can claim a 150 MPG performance for his/her share of the service. If the fleet ran entirely on liquid fuels, it would get 25 MPG per passenger. Still better than the U.S. fleet average personal car, but not by a large margin. Performance is no doubt better in less sprawling locations and in places where ridership is higher.

Of course, bus service passenger-miles per gallon is a complex subject with many logistical complications. One could achieve higher occupancy by flooding the route with buses during peak hours, running many fewer at other times. While this would be a fuel-efficient strategy, the capital cost (and embodied energy) of a standing fleet may make this impractical in other ways. Even so, packing the buses at peak times yields a fairly significant overall reduction of liquid fuel use. Even better if the buses use alternative fuels, as MTS does. The problem is further complicated by the fact that bus service is also a social service for people who can’t drive. Supporting off-peak ridership is a form of community service, even if less efficient than at peak times. Perhaps I should leave this topic for now and devote a future post to public transportation.

Other Avenues

There are other ways to reduce your share of liquid fuel consumption in society. Agriculture is a heavily fossil-fuel subsidized activity, for instance. Dietary changes can cut the associated fossil fuel use by at least a factor of two—another topic that deserves its own post. Discretionary travel by air can often be cut by a factor of two or more. Even travel for work can often be reduced once personal reduction becomes a priority. I have turned down a number of invitations to speak at conferences far away (especially overseas), partly on this basis. One might also consider solar-charged golf carts for local mobility; moving to a walkable community; more bicycling; rickshaws; whatever. There are options.

But be inventive. It is far less effective for me to provide a list of possible changes than it is for you to look at your situation and identify places where you could make a big difference.

Note: Thanks to Jim Byrne and Devin Braun at MTS for their crunchable statistics.