Human Energy vs. Oil & Gas

source: Life After the Oil Crash


1. How Much Human Energy Is Contained in One Gallon of Gas?

From Dr. David Pimentel:

"That is, the 38,000 kcal in one gallon of gasoline can be transformed into 8.8 KWh, which is about 3 weeks of human work equivalent.(Human work output in agriculture = 0.1 HP, or 0.074 KW, times 120 hours.)"

He is accounting for the energy lost in the process of converting the gasoline into usable energy.

My calculations excluding the energy lost in the conversion process are as follows:

  • 1 Gallon of Gas = 125,000 BTUs
    Source: US Department of Energy

  • 3,400 BTUs = 1 KWH
    Source: US Department of Energy, Bonneville Power Mgt.

  • 1 Gallon of Gas = 37 KWH
    (125,000 BTUs in a gallon of gas divided by 3,400 BTUs in 1 KWH)

  • 1 Gallon of Gas = 500 hours of human work output
    (37 KWH in 1 gallon of gas divided by human work output in agriculture of .074 KW = 500 )

  • Of course, there is some wiggle room with this number. Construction work, for instance, might yield a slightly different number. The size and physical condition of the person performing the work would also make a difference.

2. How Much Human Energy Is Contained in One Barrel of Oil?

  • 1 Barrel of Oil = 5,800,000 BTUs
    Source: Louisiana Oil and Gas Association

  • 1 Gallon of Gas = 125,000 BTUs
    Source: US Department of Energy

  • 1 Barrel of Oil thus contains the energy contained in 46.4 gallons of gas
    (5,800,000 divided by 125,000 = 46.4 )

  • 1 Gallon of Gas = 500 hours of human work output
    Source: Calculations Done Above

  • 1 Barrel of Oil = 23,200 Hours of Human Work Output
    (Energy equivalent of 46.4 gallons of gas per barrel of oil x 500 hours of human work ouput per gallon of gas = 23,2000)

3. How Much Energy is Used to Construct a Car?

This number is a bit hard to pin down. The most frequently cited estimates I've come across are that the average car will consume during its construction 15-30% of the energy used during its lifetime.

  • In the US, the average car has a lifetime of 10 years and will consume on average, 750 gallons of gas per year.

  • 10 years x 750 gallons of gas = 7,500 gallons of gas consumed during a car's lifetime;

  • 1 gallon of gas = 125,000 BTUs;

  • 7,500 gallons consumed x 125,000 BTUs per gallon = 937,500,000 BTUs consumed during the car's lifetime;

  • 937,500,000 x 15%-30% = 140,000,000 - 280,000,000 BTUs consumed during the car's construction;

  • 140,000,000-280,000,000 BTUs consumed during construction divided by 5,800,000 BTU's in one barrel of oil = the energy contained in 24 - 48 barrels of oil to construct one car.