The Vatican has installed 2,700 photovoltaic solar panels on the roof of its Paul VI Auditorium. The panels, $1.5 million gift from the German company, Solar World will generate 300 kilowatt hours annually, more than enough to power all the lighting, heating and air conditioning for the 6,000 seat hall. Excess power will be fed into the Vatican's electrical grid.
The Vatican is already carbon neutral by some estimates. It offsets all of its greenhouse gas emissions by purchasing renewable energy credits and carbon certificates. The Vatican is also the owner of enough forest in Hungary to completely offset all of the carbon emitted by Vatican City, which is now the only soverign state in the world that can boast of being carbon neutral.