There are a lot of stories saying that people became millionaires because of Bitcoin. One example is Elon Musk, who, through his electric car company, Tesla, has made over $ 900 million (£ 646 million), after purchasing a $ 1.5 billion (£ 1 billion) worth of cryptocurrency. In fact, Musk's support in Bitcoin helped push its price above $ 58,000.

But according to US Treasury Secretary Janet Yellen, using the cryptocurrency is "a completely inefficient method of conducting transactions." She said it requires too energy-intensive processes.

Although it is unclear exactly how much energy Bitcoin uses, cryptocurrencies itself are difficult to track. But everyone agrees that Bitcoin mining is a very energy-intensive business.

In fact, Bitcoin uses the same amount of energy as the Netherlands.

In a study conducted by the Cambridge Centre for Alternative Finance (CCAF), it was found out that on a yearly basis, Bitcoin's total energy consumption is between 40 and 445 terawatt-hours (TWh). Its central estimate, meanwhile, is around 130 terawatt-hours.

Bitcoin needs this enormous amount of energy because of the computing power required to develop a blockchain that underlies the cryptocurrency.

In short, mining relies on a vast, decentralized network of computers. These "miners" allow the creation of new bitcoins, and also independently verify and record every transaction made in the currency.

Bitcoins are the reward that miners receive for accurately maintaining this record.

"It's like a lottery that happens every 10 minutes," explains Gina Peters, a professor of economics at the University of Chicago and a research fellow at CCAF.

Data centers around the world strive to compose and send transaction records in a way that is acceptable to the system. They also have to guess a random number.

The first to submit the entry and the correct number will receive a prize, which becomes the next block in the block chain. And as soon as one lottery ends, a new number is generated, starting over the whole process. According to Professor Peters, the higher is the price, the more miners want to participate in the game.

Another factor that drives Bitcoin's energy consumption is the fact that the software ensures it always takes 10 minutes to solve the puzzle. So if the number of miners increases, the puzzle gets harder, thereby raising the computing power needed to be invested in it.

The idea is that the more computers compete to support the blockchain, the safer it becomes, because anyone who might try to undermine the currency has to control and use as much computing power as the rest of the miners put together.

This means that as Bitcoin becomes more and more valuable, the computational effort expended in creating and maintaining it (and therefore the energy consumed) will inevitably increase. The tremendous effort it takes to do this also makes it difficult for Bitcoin to scale.

So if Bitcoin were to be accepted as a reserve currency, its price will likely reach millions, and these miners would have more money than the entire US federal budget.

And if this happens, world energy production will have to be doubled.

This view is supported by many figures in finance and economics.

But according to Ken Rogoff, a professor of economics at Harvard University and former chief economist at the International Monetary Fund, the two main characteristics of a successful currency are: it is an efficient form of exchange and has a stable store of value. However, Bitcoin is neither. Accordingly, this means that Bitcoin has no long-term future, and that it exists solely as a vehicle for speculation.