It could be that people become charged to a certain extent, or that they become magnetized, which allows them to affect electricity, because of the immense energy in the Upside Down. The lights went off when the Demogorgon broke through into the Right Side Up, perhaps because the monster has been charged with this energy for a long period of time in the Upside Down. When the older group are in the Creel house in the Upside Down, they begin to talk to their friends through the lights. The electrical field of the Upside Down has a far reach, and this further confirms that the electricity feeds off of each other in a way.
The infrastructure in the Right Side Up seems to be the same as that in the Upside Down. It is possible that the tear in time and space resulted in a huge amount of dormant energy in the Upside Down, which could be the reason for electrical disruption. In season 2, the arcade sign in the Upside Down still lights up, as does the Starcourt Mall entrance. The Right Side Up would be affected by this because it would increase the reach of electrical fields. Nancy cries for help in Stranger Things season 2, and the older group in the Upside Down can hearDustin in season 4.
A worker in the Hawkins Lab is sent to the Upside Down to fix a power box when their equipment goes down. The power comes back on in the right side up when this is fixed. The hallway lights in the Byer house of the Right Side Up were activated by Joyce and Hopper walking past them. The two dimensions are very thinly veiled, so it makes sense that a huge system like electrical infrastructure would show some signs of being affected in general. It would take a lot of energy to open a hole in the fabric of time and space to get to another place.
The Flea and the Acrobat is partially explained in the first episode of the new season. The motifs have become so well-known that they've been taken as common knowledge in the show. The magnetic field and gravity would be disrupted if it were open. The physics of the show has been vague and not extensively explained, but perhaps some concrete answers will come as the show heads into its final season. They talked to him about how to travel to alternate dimensions theoretically. How does the Upside Down affect the show so much? When the phone would shoot electric sparks and fry itself, Joyce could hear intense breathing through the receiver.
At certain points in the show, the characters can hear each other. There is an explanation for why this is. The alternate dimensions are folded in on the mirror image dimensions.
The Byers' home was the starting point for the technology interferences.