Energy Tech Talk

Let's Talk Energy with... J.M.K.C. Donev and E. R. Lloyd

Canadians are being bombarded with information from various energy stakeholders attempting to get Canadians to change the way we make decisions about energy. There are a number of words that are used as if they are interchangeable, which makes it hard for Canadians to make good energy choices. We need to agree on clear definitions of important words in this debate before we can engage in meaningful conversations.

This post distinguishes between two words that are often used interchangeably in the energy debate: “renewable” and “sustainable.” Not only do these words not mean the same thing, but the difference is essential to talking about energy in our society. Not everything renewable is sustainable, and in turn not everything which is sustainable is necessarily renewable. Using money as a metaphor can help understand this key distinction.

Renewable energy

Renewable resources replenish with time, like the sunlight striking the Earth’s surface, water in a reservoir, or the wind blowing. Renewable energy uses one of these resources. Renewable resources do not have a fixed quantity - more can always be generated. However, if the rate of use exceeds the rate of renewal - that is, we use more than is being recreated - our use may become unsustainable. For specific examples, please see our next post “When renewable energy isn’t sustainable.”

Resources are considered non-renewable if they take a very long time to be created (e.g. fossil fuels) or if their creation is not likely to happen again (e.g. uranium, thorium).

Sustainable energy

Sustainable energy is energy production that can last for the foreseeable future with very limited harm—often the next few decades, after which point the technological landscape will have changed enough that practices will need reevaluation anyway. Sustainable energy practices rely on which resources we use and how we use them so that they can continue to supply our needs.

Even renewable resource use may become unsustainable. If a resource is used up faster than it can regenerate it will deplete despite its renewability. If a limited, non-renewable resource is used without caution, these too may become depleted in a short time.

It’s important to note that sustainable energy practices, by the definition of sustainability, must not cause accumulated damage to the environment which may cause significant problems over time.

Money Metaphor

A good way of understanding the difference between "sustainable" and "renewable" is to put it in context of monetary income (the conservation of energy has been nicely explained in terms of money elsewhere1. If energy were money, a renewable source of income is one that would recur, like a paycheck, while a non-renewable source would be non-repeating, like receiving an inheritance.

A sustainable source of money funds a desired standard of living for an extended period of time, while a non-sustainable source of income would fail to fund that standard of living.





Yearly salary of $100,000

A stipend of $100 per month


Winning $1,000,000,000 in the lottery

A one-time scholarship for $2500

Sustainability isn’t black and white

A source of income (renewable or not) becomes less sustainable when supporting more people or a higher standard of living; energy sources become less sustainable with increased energy use due to world growth in population and, in fact, standard of living.

Canadians want to make energy choices that work for us now and in the future. These choices have to be sustainable, whether or not they are renewable and will have to continue to be reviewed in the future as technology and needs change. We can’t go to sleep at the wheel.

  1. R. Knight, “The parable of the lost penny”, Physics for Scientists and Engineers, 2nd ed. San Francisco, 2008, ch 10 pp. 268
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