Long term cost of using cryptocurrencies I'm not an economist but....

What are some way of determining whether cryptocurrencies will be a cost effective way of trading compared to some established fiat currency like USD?

In other words, might the cost of computing power and other costs necessary to trade cryptocurrency exceed the overhead costs of trading in say dollars?

What are some economics vocab words that are useful in this question?
I see what you are trying to convey. What is the cost of doing business in the Bitcoin compared to doing business with say the US Dollar? The Dollar was never designed to be ported into an international digital spectrum. It requires a massive support network of banks, regulations, payment processors and international agreements to permit Online commerce, but even then it suffers from fraud and sovereign manipulation.

The Bitcoin resolves a huge set of issues the dollar suffers from at the cost of global transaction verification and the risk of a deflationary spiral. In short, no one can legitimately assert to fully understand the impact of the Bitcoin and its long term use. It's an experiment. 

I would encourage you to take my course on Bitcoins on Udemy when I finish it at the end of this week. Send me an email at Charles.Hoskinson@gmail.com if you're interested.