There is a growing push for cities and businesses across the country to strive to use 100 percent renewable energy.

The U.S. Conference of Mayors in 2017 approved a resolution supporting a 100 percent renewable energy goal by 2035. Businesses such as Coca-Cola, BMW Group, Bank of America, and others have committed to being 100 percent renewable. Budweiser unveiled a commercial during this year’s Super Bowl to announce its beer is being brewed by 100 percent renewable (wind) energy.

But what exactly does being “100 percent renewable” really mean from a technical standpoint? Renewable energy from resources such as wind and solar aren’t available all the time to produce energy, so how is a city or business able to claim to be 100 percent renewable?

The answer lies in financial arrangements as opposed to the actual energy received from the operation of the electric grid.

To understand what being “100 percent renewable” means, it helps to have a basic understanding of how the electric grid works.

To ensure reliability, electric grid operators must maintain a proper balance in matching electric load to electric demand at all times. Renewable energy resources such as wind and solar are inherently intermittent. To respond to this intermittency, other resources are required to maintain a proper balance of electric load and demand.

If a city or business (assuming its hooked up to the U.S. electric grid) claims to be 100 percent renewable, what they are indicating is they have made financial arrangements to purchase the equivalent electric load output from renewable energy resources equal to their business or city’s electric demand over a certain period of time. Being connected to the electric grid, they are receiving electricity produced from whatever generating sources are on the grid — this includes natural gas, coal, nuclear and other forms of electric generation.

Once on the electric grid electricity produced by renewable sources is no different from electricity produced from other generating sources. In other words: An electron is an electron once produced. Electrons produced by renewable resources are mixed with electrons produced by more traditional baseload resources. This mix of electricity is then transmitted throughout the grid serving electric demand with no distinction on a business or city’s renewable claims.

Knowing this concept helps in understanding the current limitations of renewable resources, the importance of baseload resources to maintain a reliable grid, as well as the phrase of being “100 percent renewable” — as it relates to a financial arrangement rather than from an operational standpoint.