Cooper, who did not seek bail, was remanded in custody until January 17. Pirini was remanded on bail and is also due back in court on January 17.
The man are accused of shooting at insulators on a series of power pylons supplying the Far North about 3am on December 8.
The incident took place on a remote forestry road near Matawaia. Power was cut to about 32,000 homes and businesses for 12 hours.
The cost to Bay of Islands businesses alone has been put at tens to hundreds of thousands of dollars.
Cooper and Pirini were arrested when police searched four homes in Moerewa on Thursday.
Lawyer Tony Shepherd applied for interim name suppression, saying the men were part of a larger group, some of whom could also face charges in future.
He also said Cooper and his son had the same name, which could lead to confusion.
Prosecutor Duncan Coleman, however, said police were satisfied they had the men responsible.
They had spoken to one other person but he had not been charged.
Given the difference in ages between father and son it was unlikely anyone would confuse the two.
Name suppression could be granted only if publication would cause extreme hardship, Mr Coleman said.
JP Keith Hingston, who heard the case, declined the application for name suppression.
Pirini's bail conditions include a night-time curfew, not to possess firearms or ammunition, and not to consume drugs or alcohol.
As the hearing ended Mr Hingston offered Cooper and Pirini some advice.
"A very wise gentleman about 3000 years ago said: 'Those who walk with the wise will become wise. Those who walk with the stupid will fare badly'. Think about that before you do silly things."
The maximum penalty for intentional damage is seven years jail.
