Alice and the Red Queen running faster and faster to stay in the same place. ERoEI.

Alice, the Red Queen and Energy

Faster and Faster

In Lewis Carroll’s famous story Through the Looking Glass, Alice meets the Red Queen. Suddenly, they start running.

Alice and the Red Queen running faster and faster to stay in the same place. ERoEI

The most curious part of the thing was, that the trees and the other things round them never changed their places at all: however fast they went, they never seemed to pass anything. 'I wonder if all the things move along with us?' thought poor puzzled Alice. And the Queen seemed to guess her thoughts, for she cried, 'Faster! Don't try to talk!' . . . and still the Queen cried 'Faster! Faster!' and dragged her along. 'Are we nearly there?' Alice managed to pant out at last.


'Nearly there!' the Queen repeated. 'Why, we passed it ten minutes ago! . . . 'Faster! Faster!' And they went so fast that at last they seemed to skim through the air, hardly touching the ground with their feet, till suddenly, just as Alice was getting quite exhausted, they stopped, and she found herself sitting on the ground, breathless and giddy. . .


. . . Alice looked round her in great surprise. 'Why, I do believe we've been under this tree the whole time! Everything's just as it was!'


'Of course it is,' said the Queen, 'what would you have it?'


'Well, in OUR country,' said Alice, still panting a little, 'you'd generally get to somewhere else—if you ran very fast for a long time, as we've been doing.'


'A slow sort of country!' said the Queen. 'Now, HERE, you see, it takes all the running YOU can do, to keep in the same place. 

This image of Alice and the Red Queen running faster and faster just to stay in one place, is an excellent way of looking at any peak resource issue, particularly the basis for the concept of 'Peak Oil'.


In the early days of the oil industry, very little energy was needed to find and develop new sources of crude. All that they had to do  in those days was “stick a straw in the ground” and oil flowed. The picture below shows a gusher from an oil well in south-east Texas sometime around the year 1900. The oil reservoir was close to the surface and had sufficient internal pressure to drive the oil as shown.


Oil companies, for example, have to spend ever increasing amounts of money to find replacements for their depleted reserves of crude oil just to stay in one place — they never get ahead of the game.

Oil well blowout / gusher — high ERoEI

Fast forward a hundred years and we see that new sources of oil are difficult to find and extremely expensive to develop. An offshore platform in deep water, such as the one shown, can cost billions of dollars. The oil industry is running faster and faster to stay in the same place.

Offshore platform needs very large investment due to low ERoEI

Fast forward a hundred years and we see that new sources of oil are difficult to find and extremely expensive to develop. An offshore platform in deepwater, such as the one shown, can cost billions of dollars.

Energy Returned on Energy Invested

The phrase, “It takes money to make money" is commonly used in the financial world. The same concept applies to energy.


It takes energy to find and utilize energy.

Net Energy

In order to understand the economics of the oil business, it is necessary to distinguish between Gross Energy and Net Energy.

The crude oil that flows out of a well contains ‘gross energy’. It is the total amount of energy that the oil can provide when burned. However, before that oil can be supplied to a customer it has to be transported to a refinery and turned into usable products such as gasoline, aviation fuel and feedstock for petrochemical plants. All of these activities consume energy. The energy in the produces provided to the customers is ‘net energy’.

Net Energy  =  (Gross Energy  -  Energy Expended)


Another way of looking at the same concept is to consider the term ‘Energy Returned on Energy Invested’ or ERoEI. It can be defined as follows.


ERoEI  =  Gross Energy / Energy Expended


Let’s say that the crude oil that flows out of a well contains say 100 units of energy (Btus or kilojoules are commonly used units of measurement). Let’s further say that 10 units of energy are consumed in finding and developing the oil well in the first place, and then transporting and refining the crude. Then,

Gross Energy = 100 units, Energy Expended = 10 units and Net Energy = 90 units.

The Energy Returned on Energy Invested, ERoEI = 100/10 = 10

With regard to crude oil, we have exploited the easy-to-find and easy-to-develop resources first. We have picked the low-hanging fruit. Therefore, oil companies are forced to spend an ever-increasing amount of energy simply finding and extracting new sources of energy to replace what has been used.

It is thought that, in the early days of the oil industry ERoEI values were as high as 99, i.e., it took just 1 unit of energy to find and develop 100 units of gross energy. Over the years, as new sources of oil have become increasingly difficult to find and develop, ERoEI has fallen into the 10 - 20 range.

From a mathematical point of view, if ERoEI falls below 1 then there is no point in continuing the work because more energy is being spent on getting the oil than that oil eventually delivers to the market place. In practice, many observers suggest that, if the ERoEI value falls below 5 then there is little incentive to develop that source of oil.


One reason for this conservatism is that there are many factors that go into finding and developing new sources of oil that are not normally considered in the development of the ERoEI value. For example, government subsidies will skew any analysis. It is also difficult to define the boundary conditions and to determine which activities to include in the calculation. 

Representative ERoEI Values

The concept of gross and net energy can be applied to any energy source. Shown below are representative ERoEI values for different sources of energy. Actual values will vary considerably depending on the specific circumstances.

  • Hydro                                        100

  • Oil (conventional onshore)               20

  • Wind                                          18

  • Oil imports                                   12

  • Natural gas                                  10

  • Solar                                             5

  • Shale oil                                        5

  • Bitumen tar sands                            3

  • Ethanol from corn                    <1 to 5

The Energy Cliff

The following chart shows the relationship between Net Energy and ERoEI. It shows that when ERoEI reaches a value of about 5 the return on energy invested drops precipitately.  We fall off the energy cliff.

Energy cliff: net energy drops quickly when ERoEI falls below 10.

As ERoEI declines, so does Net Energy. When ERoEI remains above 10 plenty of Net Energy is available. However, at that point the amount of energy available for use starts to decline steeply. When ERoEI is less than 5 very little Net Energy is available. This phenomenon is sometimes referred to as the Energy Cliff.

If the oil industry reaches that point then the industry can no longer be profitable and it will need to shut down. This is why the phrase ‘Peak Oil’ does not mean that we run out of oil. It means that we run out of affordable oil.

his way of thinking challenges the standard economic statement that, “If prices go up then supply will increase correspondingly”. No amount of money will justify the development of new resources if the resource itself is required for the development process, and if that resource is in irreversible decline.