Tesla Japan Puts a Powerwall 3 Underwater to Show Its Flood Rating

A Powerwall 3 stands in a water-filled aquarium in Tesla Japan’s flood demo. Credit: Tesla Japan/X

Tesla Japan has posted a video of a Powerwall 3 home battery standing in a water-filled aquarium to show off its flood rating, and Elon Musk reposted the clip to his followers on Friday morning.

The post went up at 1:15 a.m. PT (5:15 p.m. in Tokyo). Translated from Japanese, it reads: “Tesla’s home battery Powerwall 3 can handle flooding up to a water depth of 0.6 m,” followed by a fish emoji. Musk reposted it at 7:33 a.m. PT.

The 33-second video opens underwater, looking through the glass at the battery’s white front panel past aquarium plants and tiny astronaut figurines. A wide shot then shows the top of the Powerwall, Tesla logo and all, standing above the waterline. From there, a woman moves through a dark set using a fridge, a stove, an espresso machine and a TV. The clip closes on the Tesla app for “115 Algae Ave,” showing a grid outage and the message “Powerwall is providing backup power.”

The 0.6 m figure has been on the spec sheet since launch. When Tesla Japan launched Powerwall 3 on August 3, its press release listed flood resistance “up to 60 cm from the bottom edge” as a feature added over Powerwall 2. It sits alongside dust protection, heavy salt-damage resistance for coastal homes and an operating range of -20 to 50°C.

Tesla’s North American Powerwall 3 datasheet rates the battery and power electronics IP67 and the wiring compartment IP55, inside a NEMA 3R enclosure. That sheet doesn’t list a flood depth.

For anyone new to it, Powerwall 3 is Tesla’s 13.5 kWh home battery with a solar inverter built in. Japanese units are rated for 9.69 kW of output and carry a 10-year warranty, and Tesla Energy touted it as “Built for Japan” in September, with installs starting this fall.

Flood resistance matters because home batteries usually sit outside at ground level, right where water collects in heavy rain. The storms that knock out power are often the same ones that flood the yard, which is exactly when a backup battery needs to keep working. Tesla has played this card before, cheering a Powerwall that kept working after hours underwater during Hurricane Ian in 2022, and its Storm Watch feature tops batteries up before severe weather hits.

Neither the post nor Tesla’s documents say how long Powerwall 3 can stay submerged, or whether the 60 cm figure covers the less-sealed wiring compartment. Tesla hasn’t said whether the same rating applies outside Japan, what the warranty covers once a unit has sat in floodwater, or whether it needs an inspection before going back into service. The video also doesn’t show whether the unit in the tank was the one running those appliances.

The demo caps a busy week for Powerwall, after 85,774 California Powerwalls sent 601 MW to the grid. In Japan, Tesla is pitching something simpler: when the water rises, the battery is supposed to keep the lights on. Whether anyone wants an aquarium wrapped around theirs is another question.