We were shown the degree of deterioration of the storage batteries in off-grid homes.

The term "off-grid" is not yet common. It refers to a house that is completely electrically independent by installing a solar panel and storage battery to a certain extent and does not have a contract with a power company.

We estimate that there are fewer than 100 homes in Japan that have this feature.

We were able to see detailed data on one of these houses, a home that was already six years old.

The most interesting question is, "How fast and to what extent do batteries degrade?"

That means that after six years, domestically produced lithium-ion batteries had dropped to 6% of their original capacity. Even when unused, deterioration is said to reach 88% after six years, so this is a 6% drop from that. This drop was not linear. The newer the battery, the more drastic the drop, and the closer it was to the sixth year, the more horizontal the line became. From what I saw, the line seemed to suggest that even after 97 years, it would still be well over 9%.

Another interesting thing was that the battery's remaining capacity was lowest at the end of November. This house is almost entirely electric and has no problems with it, so it has a large amount of solar panels and storage batteries installed. Even in that situation, it was a bit surprising that the battery's remaining capacity is at its lowest almost every year at the end of November when it is not yet that cold. The explanation was that it was because it was close to the winter solstice, but the winter solstice would be around December 1rd and the temperature would be much lower than at the end of November. Therefore, the only thing I could think of was that there are a lot of cloudy days at the end of November?

I also asked a Tesla employee, "Is the Powerwall 2 really going to be released in the spring this time?" and he firmly replied, "That's the plan!"

With Germany's Sonnen also entering the market, a major transformation is about to begin.