U.S. airstrikes against the Islamic State's oil infrastructure are starting to have an effect, as reports on the ground indicate that infrastructure is beginning to falter and the price of oil, gasoline and kerosene is skyrocketing.

The U.S. has been conducting regular airstrikes against oil refineries and transport trucks for the past several months as part of Tidal Wave II, named after a previous Tidal Wave operation that tried to take out the Nazi's access to oil. Administration officials said last month that they are beginning to see truck drivers charge the terrorist group more to transport its oil, but said that it's too soon to tell if the strikes are having any major impacts on the Islamic State's ability to operate.

However, through interviews with locals on the ground, the Iraq Oil Report released a study on Monday that found the strikes are putting the terrorist group at a disadvantage. A gallon of unleaded gasoline or kerosene in Mosul now costs about $6.31 per gallon, according to residents, more than four times the price in summer 2014.

Early last year, the Islamic State also had enough oil to provide six hours of electricity a day for residents of areas it controls. Now, the terrorist group is experiencing fuel shortages and struggling to provide basic services like electricity and running water.

"Everything used to be okay," an Iraqi resident who fled the area in November told interviewers. "We had food, fruits, fuel. But this started to diminish in 2015. ... Now, there isn't healthy drinking water, and foods and medicines are in short supply. The people are suffering from despair because Daesh is controlling their fate."

Lawmakers largely praised the military's effort to take out the Islamic State's ability to profit from oil, but criticized the administration for taking so long to focus its efforts on this source of income.

"ISIS has been bringing in at least $1 million a day from black market oil sales to fund their global terrorist operations, yet we have just now started hitting their oil trucks a few weeks ago," Rep. Martha McSally, R-Ariz., said in a statement earlier this month.

But administration officials said information collected during a raid in May allowed it to be more precise in what pieces of the oil infrastructure it targeted, and that it took months to translate and understand the large number of documents. Some officials have also said the administration was slow to target oil for fear of environmental repercussions.