The average solar home produces 20-40% extra energy than it can make use of. This excess energy is then sold back to the energy provider, but only for what it cost the home to produce the energy, so homeowners make nothing off the sale in the end. The energy companies then resale the energy for triple the price.
By creating a mutually beneficial trade, all of North Carolina receives new solar roofs for free, but in exchange, Tesla and SolarCity own the rights to the excess energy and do not have to purchase any of it back.
North Carolina is restored, and after just 3 years Tesla and SolarCity don't only break even on their costs of installing the roofs, but they start turning a never ending profit (for as long as the roofs last) for their part in restoring North Carolina.