In an article published by Hudsom Institute, it is said that Iran is in the list of the eight great powers of 2016.

“The biggest change in the list of great powers this year is the arrival of a newcomer: Iran, the most powerful Shia country in the world,” the article said.
The other countries in the list are the U.S., Germany, Japan, China, India, Russia, and Saudi Arabia.

Following is an excerpt of the article:
Overall, 2015 was a year in which most of the great powers saw their ability to control events beyond and sometimes within their boundaries decline. With the exception of Iran, which gained strength during the year thanks to its diplomatic successes and the consequences of Russian intervention in Syria, 2015 was a year in which policy missteps and rates of relative decline had more of an effect on the power rankings than actual achievements and successes.
The most dramatic development in 2015 was that Iran catapulted into the ranks of the great powers, expanding their number to eight.
Iran had a claim to the title of preeminent power in the Middle East even before the developments of 2015. But as long as Tehran remained isolated by sanctions, its reach and capabilities were limited. The nuclear deal orchestrated by Washington allowed Iran more geopolitical reach: the unfrozen funds alone amount to 20–25% of Iran’s 2014 GDP according to some estimates, and lifting the international sanctions regime will boost the economy even more.