Both men were final-year University of the West of England students.
During sentencing, Judge Justice Linden told Coughlan: "Collins was an idealist who took an interest in the problems of the world and society.
"It comes with great shock that anyone chose to do what you chose to do to him.
"I'm sure you were planning to kill Collins and had been for some time.
"Your guilty plea came at a point in the trial when your conviction was inevitable."
During the trial, Coughlan claimed he was fearful of Collins, saying he had threatened to kill him and therefore he had "no choice" but to wait for his housemate to return from university and stab him repeatedly.
Coughlan then left his housemate to die in the alleyway behind the house they shared before cycling away on the victim's bike.
On returning home, Coughlan ate pizza and played video games, claiming he "had to disconnect" from what happened. He did not call 999 for another five hours.
The entire attack was caught on CCTV, which jurors heard Coughlan later rewatched five times.
Judge Linden said: "I do not accept your evidence that he did or said anything that made you believe he would be violent towards you in any way.
"Your evidence about these conversations was at odds with other evidence about Collins, that he was a gentle soul who was averse to conflict and confrontation."