NONE. the federal government pays 30% of the total project cost along with funding from the state, county and even your local utility. this can include up to a new roof.
You might be surprised to know that there are over 3000 to 4000 nail holes in the average median home. Adding supports for your solar system "WILL NOT" compromise the integrity of your roof. And worth noting our systems come with a 25-year roof warranty for your piece of mind.
There are many variables that must be considered. But this is a question better answered by your solar specialist.

