Sometimes we zoom down the road without knowing exactly where we are going. Then, it’s time to stop and ask for directions. When that happens on our drive to sustainable transportation strategies, we give a call to John DeCicco, senior fellow at Environmental Defense.

Moore’s Law is the empirical observation in 1965 that the number of transistors on an integrated circuit for minimum component cost, doubles every 24 months. It is attributed to Gordon E. Moore, co-founder of Intel. So, the speed and storage capacity of computers keeps going through the roof. Why can’t this happen for vehicle efficiency?


In recent years, the performance and capabilities of computer chips has increased exponentially. This growth is commonly referred to as Moore’s Law. Computer controls and batteries lie at the heart of hybrid cars. Can Moore’s Law applied to hybrids mean exponential gains in fuel efficiency?

John’s Reply

If only that were so! But until someone actually invents StarTrek-style matter transporters to transmit bodies and baggage in the form of bits and bytes—in other words, "beam us up" as data streams—Moore’s Law won’t be able to supersede the laws of motion.

Computer chips process information, which for practical purposes is massless. That’s why computer technologists can keep cramming more circuits onto chips, slashing the space and time scales for moving information and doubling processor power every two years.

Moving matter, however, is a different story. Bodies and baggage (and batteries) have real mass and take up real space. Even a very streamlined car with a perfectly efficient powertrain will require a certain minimum amount of energy to move it a given distance. Adding in all the creature comforts, performance desires and safety features we expect in our vehicles, and then factoring in the laws of physics, one soon bumps into serious practical limits for fuel efficiency. Although some advanced prime movers, such as fuel cells, do not have the same thermodynamic limits of combustion engines, they still face limitations in electrochemical energy conversion efficiency. Speaking of electrochemistry, batteries certainly have not seen Moore’s Law-like progress. Battery technology is progressing, but incrementally and often frustratingly slowly, whether the application is laptops, cell phones or cars.

Hybrid drive can indeed help any propulsion system maximize its efficiency by smoothing energy use over the variable loads of a driving cycle, avoiding fuel burn during times of minimal energy need, and recovering energy otherwise lost to braking. But hybrid technology does no more than enable engineers to achieve efficiencies that come closer to the basic limits rooted in the form and function of the vehicle. It offers no Moore’s Law magic that would let fuel efficiency grow by leaps and bounds.

That’s not to say that steady—linear, shall we say, rather than exponential—gains in fuel efficiency can’t be made. Many technology refinements offer higher fuel economy and the advent of hybrids extends that potential even further. It is not, however, a game-changer in any fundamental sense of the term. The same desires for larger, faster, more luxurious and powerful vehicles that consume other forms of automotive engineering progress can also devour much of the efficiency benefit from hybridization. In short, even technology as wonderful as hybrid drive can’t "beam us up" beyond our ability—or inability—to make fuel economy itself a priority in automotive choice and design.

Based in Ann Arbor, Michigan, John DeCicco is a Ph.D. mechanical engineer who specializes in automotive strategies for Environmental Defense, where he evaluates vehicle technologies and helps develop market-based policies for addressing the car-climate challenge. John was the original creator of ACEEE’s Green Book, which references for the its Gas Mileage Impact Calculator and lists of the "greenest" and "meanest" vehicles, and he has published widely-cited technical studies on automotive energy and climate issues.