In 2021, the average United States household consumed 11,700 kWh. Fuel consumption from all sources overall has been on a steady and sharp rise throughout the last 50 years, but if you zoom out to the late 1700s, you’ll gain a powerful perspective on the rapid growth of the world’s energy needs.

Above is a graph provided in a study by the United States EIA, estimating the history of the United States’ annual energy consumption through its history. The same type of information is available for other large countries and showcases that their energy usage occurs in relatively similar proportions.

What you’ll notice here is that  both natural gas and petroleum are the clearly dominant forces of energy in the United States.

Hydroelectric is a close third, with nuclear, coal, and wood holding up a small foundation of the entire energy usage. Truly, the rise of petroleum and natural gas unlocked the ability for the United States (like many other countries) to grow and evolve into the superpowers that they are today.

So how can this energy be easily replaced by alternative sources? Well, the answer is that it can be done, but it’s a stretch to say it could be done easily.

Analyzing Energy Density by Source

If you have a keen eye, you may have noticed in the chart referenced above that wood energy consumption has stayed about the same throughout all of the United States’ history.

While there are a lot of reasons that could explain this, the most obvious is that wood simply doesn’t yield energy in high amounts relative to the other fuel sources listed in the chart.
    

For this reason, wood serves as a good example to discuss the significance of energy density when it comes to assessing how alternative energy sources can meet the world’s energy demands.

Energy density, defined in simple terms, is the amount of energy that is able to be stored within a given source, system, or substance. Typically, energy density is measured as “energy per volume” or “per mass,” and naturally, the higher the energy density, the higher the amount of potential energy that lies within it.

Consider the following three sources of energy: coal, natural gas, and petroleum. One gallon of petroleum is equal to about 13.1 pounds of coal, which is also equal to about 160 cubic feet of natural gas.

Even though the amount of all three energy sources is equal, their energy density will be the final arbiter as to how much energy they can output.

This is usually measured in Megajoules per Kilogram. So in this scenario, the energy density of petroleum is 46MJ/kg, while natural gas has a density of 55MJ/kg, and coal has an energy density of 24MJ/kg.

The higher energy density of petroleum and natural gas gives them about twice as much potential energy as coal, even when measured in the same amount.

Considering More Powerful Alternatives

These figures matter greatly because they help us determine whether or not we’re pursuing efficient sources of energy as we seek out new renewables.

It’s prudent to ask whether or not the new fuel sources in development will offer a greater energy yield than what our existing energy streams can already provide.

One such renewable energy source worth considering is hydrogen, which has an energy density of 120MJ/kg — considerably more than natural gas and petroleum.

However, like all renewable energy, more research and development is needed in order to determine the best way to capture, refine, and store that energy for human consumption.

It is for this reason that our transition to renewable energy cannot be rushed along. New innovations are constantly happening in the world of energy, but we will naturally need time to thoroughly test and develop these innovations into viable forms of sustainable fuel to fuel humanity’s energy-dependent lifestyles.

While we work toward that transition, it’s important that we continue to supply energy through our available streams so that we keep homes heated, industries growing, and economies thriving.