I recently read the Wikipedia article on Back to the Future.  From the section on the film’s development:

Originally, Marty was a video pirate, the time machine was a refrigerator, and he needed to use the power of an atomic explosion at the Nevada Test Site to return home.  Zemeckis was “concerned that kids would accidentally lock themselves in refrigerators”, and the original climax was deemed too expensive.

The footnotes seem to indicate that this information comes from Empire magazine, but I couldn’t find the article.

Steven Spielberg produced the three BTTF films.  He also directed the four Indiana Jones movies.  Did he pluck this (previously) impractical scene from an old project?  Who knows.