You know the more I think about it, Tesla could do this in a way that would be very profitable for Tesla. It would require Tesla to basically become the new utility of PR. As long as people are going to live there, they will need power and Tesla can sell them electricity at 20c/KWh on average then they can make this happen and be very profitable. The first step is to send tons of batteries and panels and deploy them all over the island. Several large installs that are spaced out throughout the country. Run lines under ground to further distributed areas and put battery packs. Then work with citizens to buy solar for their homes that connect to the distributed power packs. Not all will so the larger microgrid setups, a dozen or so Kauai sized installs spaced around the island will be the main source for power and the power packs will be for local load balancing near the main transformers.
Telsa could make power at 5c or at worst 10c per KWh and sell it for a decent markup and people on the island would still save money and have a much more reliable grid. Because they would be a captive audience, the financing for the build out would be easy and would not be tied to the government of PR. Ofcourse the next step would be to convert all the cars to EVs so Tesla could offer special EV rates and install software to use the cars to help support the grid by taking power at peak solar times and stressing the power packs less.
Edit: Ok.. Kauai population is 65K, and PR is 3.4M so they would probably need something much much larger and way more of them. That being said, 3.4 million people paying 20c/KWh is ~$10M/Day at 15KWh per day per person.
Ties up too much capital. The return on capital is ~10-15% to provide all that hardware, while they've been getting better than 50% on all those factory build-outs (SWAG, but shouldn't be too far off)