In 2011, the International Space Station was moved to an altitude of 248 miles above the Earth's surface. Prior to the move, the ISS had an orbit of 220 miles.
The increase in altitude reduces the ISS's fuel use by over half. As Earth's atmospheric density increases due to an increase in solar activity, the ISS needs to be raised in order to reduce drag and save fuel. Since the ISS is the size of a football field and moves at 17,500 mph, even a small increase in drag can have a large effect on its altitude over a period of time.