The European Commission has set the goal for Europe to have a minimum of twenty percent of their energy used, come from renewable sources. Italy has been slow to embrace solar energy in the past. More recently, the use of solar energy in Italy has increased and the Vatican's example will likely increase Italy's solar usage even further.
It is probable that many Catholic Churches and individual Catholics will follow the example made by their religious leader and install solar energy systems.
The Pope and the Vatican are a respected presence by many throughout the world. It is plausible that environmental statements made by Pope Benedict XVI and the use of solar energy in the Vatican, will set an example that many will choose to follow.