The system, which has giant wings with a span of 73 metres (240 feet), were fitted by the orbiter's astronauts during three spacewalks.
There were some teething problems in extending the wings but overall the construction work has delighted the American space agency, Nasa.
The shuttle is due to touch down at the Kennedy Space Center in Florida on Monday at 1804 EST (2304 GMT).
Brief meeting
After completing their spacewalks, the astronauts were able to visit the crew inside the space station.
Endeavour's commander Brent Jett and his four colleagues entered the Unity module of the ISS and exchanged handshakes and smiles with the space platform's Expedition 1 crew.
Brent Jett said: "Endeavour arriving!" and entered the module, after requesting permission to open the hatch. The meeting took place 383 kilometres (238 miles) above the Pacific Ocean, near Cape Horn, South America.
The astronauts and cosmonauts spent less than a day together before Endeavour started its journey back to Earth.
Electric shocks
Although the shuttle had been docked at the space complex for nearly a week, the hatches had remained sealed for safety reasons while work took place outside.
ISS solar wings
17 tonnes
73 metres across
Cost $600m
Enough power for 30 homes on earth
One of the five brightest objects in night sky
Nasa officials have hailed the mission's success.
"It's probably the most difficult, most complicated integrated job to date, relative to what we do in human space flight operations," said Milt Heflin, deputy chief flight director.
"The whole crew was magnificent," said Nasa administrator Daniel Goldin in a congratulatory call to Endeavour's five astronauts.
The two spacewalkers also installed a camera cable and a static-electricity monitor to the outside of the ISS. The monitor will be used to gain a better understanding of how to protect spacewalking astronauts from electric shocks.
Destiny lab
Officials said the astronauts had now completed a number of tasks that needed to be carried out before the next mission to the ISS.
The space complex now has enough power to light all the modules, including the space laboratory Destiny which will be added in January.
While work was going on outside the ISS, the platform's Expedition 1 crew had tasks of their own.
Commander Bill Shepherd and cosmonauts Yuri Gidzenko and Sergei Krikalev had to deal with a malfunctioning air conditioner and a broken carbon dioxide removal unit.