Let's hope they charged them up before shipping.
The batteries are not there to supply electricity. They are there to store electricity generated from solar panels.
This requires some explanation. Most solar energy systems have no way to store power. They generate electricity and that power has to go somewhere. If the power can't go anywhere or if you can't use it all at the source, you actually have to shut them off to prevent them from being damaged. Normally that power goes to the electrical utility that transmits that power throughout the electrical grid for customers to use. There is a complicated balancing act that has to happen here, but that's the short of it.
There are isolated solar power generating systems on Puerto Rico, but those systems are almost useless without a functioning electrical power grind to transport the power around, and at the moment Puerto Rico has no electrical grid: it was mostly destroyed by the storms. The batteries can be installed at the locations where functioning solar generating systems still exist, or mated to new solar systems that can be shipped there, to provide local power. Power can be generated and stored during the day and used at night. That is extremely useful. It allows for a decentralized power generation and utilization system to be created at least sporadically throughout the region to give some electrical power back to communities.
Solar power is a great way to bring a lot of decentralized electrical power on-line in a short amount of time, but its usefulness is very severely hampered if you have no way to store the power. Solar panels + powerwall batteries can bring 24-hour power to a location without a functioning electrical utility. Which Puerto Rico won't have for quite some time.
About ten years ago there was an earthquake in Hawaii that caused the electrical grid safety systems to trip mostly statewide. On the island of Oahu (where Honolulu is located) the entire power grid basically turned off. Even though there was no damage from the earthquake itself, it took over twelve hours for power to be restored to most locations and some places were without power for over twenty four hours. We had to perform what is termed a "black start" on the island. Because we live on an island, we cannot get electrical power from neighboring states. That's a problem because almost all of the power generation plants on the island require electricity to start them, which is an interesting catch-22.
What the power company had to do was to start some special diesel generators near Pearl Harbor that could self-start. They are tiny but can generate enough power to light up that generation station. But first they actually had to completely disconnect the electrical grid from that station. It is impossible to start those tiny generators while the entire state grid is attached to them: the load would kill them. Once they were running, they had to deliberately disconnect everyone from everyone else on the grid, and then selectively open the transmission lines that would carry power from those generators to another main generation station across the island. Then use that power to start that station. Then start connecting small parts of the grid to that station and then send power to the rest of the power stations. And so on, using each station to reenergize small parts of the island and also bring up the other stations.
All this is separate from the fact that when you shut down the power grid, you can't keep the generators running so you have to shut them down, and they are steam powered plants. Simultaneously you have the problem that the generators are too hot to do anything to them initially, and then when they cool off enough to inspect and restart them all the steam has condensed to water which can destroy the generator parts, so they have to be cleaned. It can take hours to properly shut down a generator station, and then hours to properly start it again, all while needing electrical power you don't have until another station can start up.
Puerto Rico has all the problems we had, combined with most of the electrical grid and much of the power stations themselves damaged or destroyed. It could easily take months to repair, inspect, and restart the electrical grid, and even when they begin doing so it will have to happen in a slow motion phased in version of what we had to do when everything was basically okay from the start.
If you wait for everything to be fine everywhere in Puerto Rico, you could be waiting a long time for electricity. Having an alternative that can be put online immediately to serve small areas disconnected from each other is potentially a life-saving measure. The powerwall batteries are one component in a decentralized electrical option for parts of Puerto Rico.
