What’s the difference between clean, green and renewable energy?

Green energy, clean energy, renewable energy and alternative energy. What’s the difference and does it matter?

The terms green energy, clean energy and renewable energy get used interchangeably all the time. But are they really the same thing? (Spoiler alert – they are not). And what about new energy and alternative energy? Are they the same, similar or something completely different? Also, who exactly has final say on what type energy is clean or green?

We were as interested as anyone to know the answer. I mean, being a renewable energy comparison site, that’s our business right. And, with an ever-growing focus on climate change, the environment and sustainability it seems, to us at least, pretty crucial to get a grasp of the basics. Firstly, to ensure that we end up supporting the right technologies. Secondly, to avoid getting hoodwinked by false claims from rogue traders trying to sell us (maybe not so) “green” energy and, dare we say it, from governments who will need our money to pay for it.

So we got our thinking heads on, did a lot of digging around and put together this simple, yet definitive guide. We hope you find it useful.


Firstly, let’s start with some definitions. A definition is, after all, defined as a statement of the exact meaning of a word,. It seems like an obvious place to start.

We looked up definitions from some of the main authoritative English language dictionaries. Unfortunately, many dictionaries did not have definitions for the words we were searching for. Those that did therefore selected themselves. Here’s what we found.

Resource / DictionaryClean energy
Green energyRenewable(s) / Renewable energyAlternative energy
Oxford English Dictionary
(via Lexico)
Not definednoun
Renewable energy; energy produced or harnessed in an environmentally responsible manner.
(usually renewables)
A natural resource or source of energy that is not depleted by use, such as water, wind, or solar power.
[mass noun]
Energy fuelled in ways that do not use up the earth's natural resources or otherwise harm the environment, especially by avoiding the use of fossil fuels or nuclear power.
energy, as electricity or nuclear power, that does not pollute the atmosphere when used, as opposed to coal and oil, that do.
Not definedrenewables
sources of alternative energy, such as wind and wave power

renewable energy
any naturally occurring, theoretically inexhaustible source of energy, as biomass, solar, wind, tidal, wave, and hydroelectric power, that is not derived from fossil or nuclear fuel.
energy, as solar, wind, or nuclear energy, that can replace or supplement traditional fossil-fuel sources, as coal, oil, and natural gas.
Collins English Dictionarynoun
energy, as electricity or nuclear power, that does not pollute the atmosphere when used, as opposed to coal and oil.
[mass noun]
Green energy is power that comes from sources that do not harm the environment and are always available, such as wind and sunlight.
sources of alternative energy, such as wind and wave power

renewable energy
another name for alternative energy
a form of energy derived from a natural source, such as the sun, wind, tides, or waves
Also called: renewable energy
Cambridge DictionaryNot definednoun
energy that can be produced in a way that protects the natural environment, for example by using wind, water, or the sun
renewable energy
energy that is produced using the sun, wind, etc., or from crops, rather than using fuels such as oil or coal

types of energy such as wind power and power from the sun that can be replaced as quickly as they are used
energy from moving water, wind, the sun, and gas from animal waste
Sources as referencedCompiled by energyscanner.comIn no particular order...

What do the definitions tell us?

So what do we learn from dictionary definitions? Can we draw any definitive conclusions?

Unfortunately, there are several issues which make this less than clear cut.

Firstly, most dictionary sources do not cover all the different terms.

Secondly, some of the definitions are circular. For example, the Collins English dictionary defines renewable energy as alternative energy and alternative energy as….you guessed it…renewable energy.

Thirdly, some of the sources contradict each other. For example, the Oxford English Dictionary specifically excludes nuclear energy from its definition of alternative energy whereas Dictionary.com includes it.

Fourthly, some definitions focus on what the fuel source is (oil, coal, solar) rather than on its properties when used; for example, its sustainability / replaceability or environmental impact.

And so on….

And all that from just 4 of the eading authorities on words and their definitions. Although we expect that most of these dictionaries will need to revisit these entries in the not-too-distant future.

However, it does show that this topic is not so straightforward after all.

What do government agencies say?

We did a trawl of definitions from various government agencies and found one from the United States Environmental Protection Agency (EPA) to be particularly useful. The Green Power Partnership is a free, voluntary program of the EPA that aims to increase the use of green energy among organizations in the United States. Its definition of renewable energy and green energy (they call it power) are as follows.

Renewable energy includes resources that rely on fuel sources that restore themselves over short periods of time and do not diminish. Such fuel sources include the sun, wind, moving water, organic plant and waste material (eligible biomass), and the earth’s heat (geothermal).

Green power is a subset of renewable energy and represents those renewable energy resources and technologies that provide the highest environmental benefit. The U.S. voluntary market defines green power as electricity produced from solar, wind, geothermal, biogas, eligible biomass, and low-impact small hydroelectric sources. Green power has a zero emissions profile.

We believe these last 2 definitions are particularly useful as they get to the root of what these energy types are all about.

Putting it all together

So where does that leave us?

Putting the various definitions into a framework we have come up with what we believe to be simple but definitive descriptions off the various energy types covered here. But before we make our amazing revelation, we need to introduce two more, less controversial, definitions as these will be referenced below – conventional power and fossil fuels.

Conventional Power

The Environmental Protection Agency defines conventional power as the combustion of fossil fuels (coal, natural gas, and oil) and the nuclear fission of uranium. Basically, the stuff that we currently use to power modern human life on our planet.

Fossil Fuels

Fossil fuels are hydrocarbons, primarily coal, fuel oil or natural gas, formed from the remains of dead plants and animals.

The term Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed by natural processes, such as the anaerobic decomposition of buried dead organisms (plants and animals) that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth’s crust over millions to hundreds of millions of years.

Although fossil fuels are continually formed by natural processes, they are generally classified as non-renewable resources because they take millions of years to form and known viable reserves are being depleted much faster than new ones are generated.

energyscanner.com Definitions


We believe that it comes down to this.

Whether or not an energy source is clean is ultimately about emissions of carbon dioxide and other pollutants that arise from the use or burning of the fuel source. At a secondary level, it may also be about of the environmental damage that is caused in the extraction of the fuel, the construction of otherwise clean energy power plants and / or the disposal of any waste materials.

Whether or not an energy source is renewable is ultimately about whether the energy source is depleted by use. A renewable energy source must be either inexhaustible or replaceable by new growth over reasonably short periods of time.

Green energy is the intersection of clean and renewable energy. It is energy derived from renewable energy resources that does not pollute the atmosphere when used. Green energy ideally has a zero emissions profile.

Alternative energy is the most ambiguous and difficult term to define.

Alternative energy appears to have morphed into a “catch-all” term for anything that isn’t conventional energy. Within that, there seems to be an implicit assumption that it is synonymous with clean, green and renewable energy. But that is not a given. As such, it is not particularly surprising that even respected dictionaries struggle to come up with clear definitions.

We suspect this is probably because this area is rapidly evolving. So, for now, it has been deliberately left wide open to allow for the inclusion of emerging technologies, the clean, green and renewable credentials of which are yet to be tested or established. In a fairly rapidly evolving environment, this seems to us perfectly reasonable.


We propose the following definitions (aiming for brevity as much as possible).

Clean energy is a source of energy that does not pollute the atmosphere when used.

Renewable energy is a source of energy that Is either not depleted by use, or which restores itself over short periods of time and which, therefore, does not diminish over time.

Green energy is energy derived from renewable energy resources that does not pollute the atmosphere when used. It has a zero emissions profile.

Green energy (light)

(A looser alternative to pure green energy providing some degree of flexibility over the level of emissions – definitely not one for the hardcore environmentalists).

Green energy is energy derived from renewable energy resources produced or harnessed in an environmentally responsible manner.

Alternative energy is energy from non-conventional resources aimed at providing clean, green or renewable alternatives to the use of earth’s non-renewable natural resources as fuel sources.

Notes and Caveats

In the context of renewable energy, we believe that short periods should be considered in terms of human generation times with very low (even fractional < 1) to low single digits being considered an upper bound.

We have omitted the use of the commonly used words “natural resources” from the definition of renewable energy as it seems to be beyond the essence of what it is to be renewable. Further, it allows for the inclusion of potential new energy sources such as the nuclear fusion of hydrogen. The United Nation Report of the World Commission on Environment and Development – Our Common Future considers nuclear fusion to be a renewable energy source yet it is most certainly not natural (at least not on Earth).


The Problem

Our investigation shows that most current definitions of clean energy, green energy, renewable energy and alternative energy are not just imprecise but also often inaccurate and conflicted. And while these terms are often used interchangeably to represent the same “thing”, that characterisation is actually incorrect. For example, although all green energy is, by definition, renewable, not all renewable resources are green. Firewood is renewable but is not green (because it is not clean – burning firewood is in fact highly polluting). Nuclear energy (fission) is definitely low carbon (zero carbon in fact) and so is technically clean, but it is not a renewable resource. It gets depleted by use and certainly does not restore itself over short periods of time.

Indeed, nuclear energy (fission) remains a controversial energy source which generates much heated (excuse the pun) debate. Many would argue that it is not a clean energy source because of the environmental costs associated with building power plants and disposing of radioactive waste. However, that is not a subject for this article.

All of this of course creates plenty of scope for confusion, data manipulation and misleading marketing in the current and forthcoming “green” revolution. Not just from corporations but also politicians (who will badly need our taxes), regulators, lobbyists and special interest groups. And we expect to see plenty of conflicting and confusing messages from all of these groups.

A possible solution

The reality is that all fuel sources lie on a spectrum of renewability versus environmental pollution.

In the very long run (by which we mean millions to 100’s of millions of years) everything is ultimately renewable – even fossil fuels. On an even longer time frame everything will ultimately diminish – even the sun will fade away on a 5-billion-year view. However, as the EPA puts it, the renewable source needs to be replenished over short periods of time. A time period measured in human generation times, provides for a framework against which energy sources can be categorised. Over such a time frame, solar and wind energy will definitely not diminish and are effectively inexhaustible. Fossils fuels (natural gas, oil, coal) however will dimmish and are clearly not renewable.

To add some clarity to the debate we have put forward concise definitions that we believe capture not just the essence of what the terms mean but also provide a framework against which energy sources can be categorised and better understood.

We would welcome constructive feedback irrespective of whether you agree or strongly disagree. Please send us a note via our Contact Us page or via Twitter.

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  –  UK Fuel Mix

Renewable Energy Fuels and Technologies

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