What Is Green Energy?

What you will learn

• Explain what “renewable” means and give examples.
• State how EPA defines green power and where the definition applies.
• Recognise that renewable sources can still have environmental effects.

Before you start

No specialist background is needed; technical terms are explained as they appear.

What does “renewable” mean?

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

Examples help. Tomorrow’s sunshine arrives after today’s is used. The wind keeps blowing and water keeps flowing. Conventional power, by contrast, comes from fossil fuels, or from the nuclear fission of uranium.

This split does not say any source is perfectly clean. It answers one question: does the fuel source replenish quickly?

How is green power defined?

According to EPA, green power is a subset of renewable energy. It covers the renewable resources and technologies that provide the greatest environmental benefit. Within the US voluntary market, green power is electricity produced from solar, wind, geothermal, biogas, eligible biomass and low-impact small hydroelectric sources.

There is one more condition. To qualify as green power, this renewable electricity must go above and beyond what is otherwise required by mandate or requirement. In other words, it is voluntary, or surplus to regulation. Customers often buy green power for its zero-emissions profile and carbon-footprint reduction benefits.

Note the scope. This is the definition of the US voluntary market. Elsewhere, terms and conditions can differ, so it should not be treated as a universal definition.

Do renewable sources have no environmental effects?

They do have effects. The benefits of renewable energy are substantial, but some renewable technologies can affect the environment. For example, large hydroelectric resources can involve trade-offs for fisheries and land use. That is why EPA counts only low-impact small hydro as green power.

Comparing with conventional power shows the difference in environmental costs. Fossil fuels have costs from mining, drilling or extraction, and they emit greenhouse gases and air pollution when burned. Nuclear power emits no greenhouse gases during generation, but it does require mining, extraction and long-term radioactive waste storage.

The takeaway is that power sources do not share the same environmental benefits and costs. A “green” label tells you a source falls within some definition. It does not replace looking at each project.

Real-world example

Suppose a company in the United States wants to buy green power. First it asks what sources the electricity comes from. Solar, wind, geothermal, biogas, eligible biomass and low-impact small hydro are all on EPA’s list.

Second, it asks whether the electricity goes beyond what is mandatory. If it only meets what the rules require, it does not count as green power under this definition. Third, it looks at the project itself, for example how a hydroelectric dam affects fish and land.

Common misunderstandings

Renewable and green power are not the same thing. In EPA’s definition, green power is a narrower subset of renewable energy.

It is wrong to assume every renewable source has no environmental impact. Large hydropower is an example with trade-offs for fisheries and land.

EPA’s definition applies only to the US voluntary market. It is not a global convention.

Frequently asked questions

Does EPA include wind in its green-power examples?

Yes. Solar, wind, geothermal, biogas, eligible biomass and low-impact small hydro are all in EPA’s list.

Does all hydropower have the same impacts?

No. Large hydropower can involve trade-offs for fisheries and land use, so EPA counts only low-impact small hydro.

Is a green label enough to assess a project?

Not on its own. You also need the source, whether it exceeds requirements, and the project’s actual effects.

Summary

• Renewable means a fuel source that replenishes quickly and does not diminish.
• Under EPA, green power is a subset of renewable electricity in the US voluntary market.
• Every source has trade-offs, so each project needs its own look.