Now that Tesla has officially acquired SolarCity, it's not wasting any time showing what the combined entity can do. Tesla has revealed that it's running the island of Ta'u (in American Samoa) on a solar energy microgrid that, at 1.4 megawatts, can cover "nearly 100 percent" of electrical needs. It's not just the 5,328 solar panels that are key -- it's the 60 Tesla Powerpacks that offer 6 megawatt-hours of energy storage. While Ta'u is normally very sunny, the packs can keep it running for three days without sunlight. They don't have to worry about a cloudy day leading to blackouts.