The US Pentagon submitted its 2016 budget, where through a series of money-saving actions it was able to conserve more than half a billion dollars’ worth in expenditures in order to “fill up” (Fuel up) aircraft carrier George Washington.

Exactly 678 million USD is required for one complete round of refilling, and this expenditure was tabled by Congress, instead of the Pentagon.

What makes the refueling process of the aircract carrier so costly, however? The US warship is equipped with two nuclear reactors, which power its four propellers, which can in turn propel the massive ship at speeds of up to 30 knots. Each reactor provides the ship with a whopping 550 megawatts of power.

The USS George Washington’s reactors contain enough fuel to keep the ship moving for 20 years. The first refueling was done in 1992. Now, 22 years later, the ship needs to be refueled again, with an average price of 27.2 million USD per year.

George Washington’s refueling will take four years, while the ship is one of 11 carriers operated by the US Navy.