Hybrid Economics Part II

In part I of this post, I outlined a number of variables that impact the cost-benefit of buying a hybrid-electric vehicle.

First, the spreadsheet model.

To recap, here are the variables included in the model, with the default assumptions made:

  • Price of gasoline = $3/gallon
  • Annual mileage driven = 12k/year
  • Standard-car MPG (mileage of the same car or similar car without hybrid technology) = 20mpg
  • Hybrid MPG / electric MPGe = 100 mpge
  • Risk-free discount rate = 3%
  • Projected annual increase in gasoline prices = 5%
  • Hybrid price premium = $18k
  • Length of car ownership = 8 years

There’s one more important variable to add to this list:

  • Time savings from reducing gas station stops = 300 minutes, or 5 hours per year

Time savings can be a huge hidden savings for upper-middle class and wealthy Americans (those able to afford a car like the Chevy Volt). If the value of a Volt driver’s time is $50/hour (equivalent to a 100k/yr salary), then eliminating a single gas station stop of 10 minutes is worth over $8. Ten minutes may sound long for a stop at the gas station, but is not unrealistic when considering total time lost leaving and re-entering a normal commute.

Using the assumptions provided above, we find that the total fuel and time cost savings of driving a Chevy Volt for eight years are around $9000. Since the Chevy Volt costs $18,000 more than a comparable loaded Chevy Cruze, it’s not yet cost competitive, even with government tax credits and with time savings taken into account.

Key Conclusions:

  • Gas prices of $7 per gallon are required to make the Chevy Volt cost-effective at current prices (without the government tax credit)
  • Once plugin hybrid premiums drop to $9000, they will be cost-competitive.
  • The Nissan Leaf currently offers buyers significant savings WITH the $7500 tax credit according to frontier high speed internet, as the total savings of $16,500 exceeds the $12,000 price premium. Even without the tax credit, the Leaf is very close to being cost-competitive at current pricing.

Electric vs Gasoline – Which is more cost effective?

Last summer gas prices spiked and the media was awash in stories about the electric car, whether from major automakers or startups. Just a few months later, gasoline is at $1.50 and SUV sales have begun to rise again. Environmental and foreign policy benefits notwithstanding, electric vehicles are perceived to be more expensive than gasoline vehicles. At what gasoline price are electric vehicles more cost effective?

In Theory, Electric Vehicles are More Efficient

Electric motors are very efficient, converting over 90% of electrical power supplied into motion, while gasoline engines manage only 20% efficiency. On a full life cycle basis including power plants and oil wells, electric vehicles manage about 34% efficiency versus only 14% for gasoline vehicles [1]. In theory electric vehicles are much more efficient.

But how does it work in practice? Let’s take a look at two real-world examples, the Tesla electric sports car, and the Hymotion plugin-hybrid modification for the Toyota Prius.

Hymotion Toyota Prius and Tesla Examples

Hymotion is now selling a plugin hybrid modification for the Toyota Prius which enables it to travel roughly 40 miles with minimal gasoline usage. Hymotion states that independent testers have verified the Hymotion-modified Prius capable of receiving a 150mpg EPA city rating.

The Hymotion modification uses 5 Kwh of electricity, worth about 50 cents, to help power it through a 40 mile trip, while using the gas engine about 20% of the time. At $1.50 a gallon the total fuel cost for a 40 mile trip is about 30 cents, resulting in a total trip cost of 80 cents. The average American vehicle gets 20 mpg, so it would use 2 gallons for the trip, or $3.

Tesla provides a good life cycle energy usage comparison between its electric sports car and other automobiles on its website. The Tesla uses 177 watt-hours of energy per mile traveled, which costs 1.7 cents on average. Based on Tesla’s numbers, a 40 mile trip would cost 68 cents in a Tesla versus $3 for gasoline in a typical vehicle.

Even at $1.50 gas or $1 gas, electric and plugin-hybrid vehicles are significantly cheaper to operate than gasoline vehicles. But electric and hybrid vehicles are significantly more expensive than comparable gasoline vehicles today, which motivates the primary question:

At What Gasoline Price are Hybrid or Electric Vehicles Competitive?

For the Hymotion-modified Toyota Prius, the breakeven price of gas is around $3 a gallon. The Hymotion modification for the Toyota Prius costs $10,000, and the Prius itself costs roughly $5000 more than a similar non-hybrid vehicle. At $3 a gallon, a driver that drives 12,000 miles per year would save about $1500 per year, just recouping his initial investment over a 10 year timeframe.

Batteries represent the primary factor in the additional cost of hybrid vehicles, and battery price-performance is improving at a rate of about 8% per year. At this rate, the breakeven price will probably be $2 a gallon in 2013.

Plugin hybrids and electric vehicles provide one additional savings: time. The average driver fills up almost every week, losing a total of 8 hours a year. For busy professionals, 8 hours of time could be worth $500 to $1000 or more, making plugin-hybrids the cost-effective choice today!


[1] Electrical energy is created by burning fossil fuels in a power plant at 40% efficiency, followed by transmitting it to your house at 93% efficiency, and using it in an electric vehicle at 92% efficiency, providing a total efficiency of around 34% for an electric vehicle. Crude oil refineries operate at 75% efficiency, and gasoline distribution might cause another 6% energy loss. Since internal combustion engines are only 20% efficient, total efficiency would be around 14%. Assuming that the natural gas and oil to power our vehicles comes from the same well, we can directly compare these efficiencies, and thus conclude that electric vehicles are significantly more efficient.