Rodrigo Moreno's second international goal gave Spain an early lead in Dusseldorf, but Thomas Muller struck a superb finish to level before the interval.
Both sides – the last two winners of the World Cup – had chances to win the game, but David de Gea was the busier goalkeeper, making two brilliant saves to deny Julian Draxler and Ilkay Gundogan.
Lopetegui, though, highlighted the strengths of Germany as both European giants extended unbeaten runs that date back to Euro 2016.
"Germany are a physically stronger and faster team," said Lopetegui.
"They are more comfortable in the transitions than we are, we have played with breadth and speed in the first 30 minutes, and we have avoided those transitions.
"They were able to run, and when they can run they are more dangerous, but we had chances to score the second goal.
"It was a nice game for the spectator, open, each one with their own style and good players. It was a good show.
"Playing against the best in the world is a very nice challenge, we have taken it as such, we have had confidence in what we are in football.
"I am sure that in a World Cup match it would be different, but neither of us has taken the game as a friendly, but with rigour and ambition."
Spain were without Sergio Busquets at the base of midfield due to injury, with captain Sergio Ramos reaching 150 international appearances.
"We had Busquets down," Lopetegui added. "It was Thiago [Alcantara, in the Busquets role] and he played a good game after some time without playing.
"Very positive things from the match and we left satisfied, the challenge was beautiful and the team has been able to compete."