Tesla's Japanese subsidiary, Tesla Motors Japan, announced in October that it would start selling its home Powerwall battery in Japan in the spring of 2020. Reservations have already been made on the site, and the price is 990,000 yen, including the Backup Gateway system which manages the grid connection, but excluding installation costs and retail tax.

The first Powerwall product went on sale in 2015, but this time it will be a second-generation product sold in Japan. The Tesla Powerwall 2 is one of the most advanced residential energy storage systems in the world and it all starts with the batteries. 

“Tesla believes that the Japanese home battery market has big growth potential,” Shinji Asakura, country manager of energy products in Japan, told reporters in Tokyo.

He cited feed-in-tariffs, which had guaranteed minimum power prices to spur solar development, are starting to expire later this year.

The need for backup power supply during outages due to natural disasters also offers growth potential, he said. Tesla has installed Powerwall systems at about 50,000 sites in seven countries since its launch in 2015, a company official said.

A single Powerwall unit stores 13.5 kWh of energy, but you can link up to 10 batteries side-by-side to increase storage.

Built-in 13.5 kWh high capacity lithium-ion battery for home use. The output power is 5 kW, and, in particular, it can store enough electricity so that a family of 4 can consume about a day. High-energy appliances such as microwave ovens and dryers, and 200 V devices such as air conditioners and IH cookers can also be powered by Powerwall.

It can also be connected to a solar power generation system and is equipped with air conditioning, a water-cooled cooling system and intelligent software that transfers energy depending on the situation. In the event of a power failure, it can automatically switch to battery power and can be used as a backup power source.

The Tesla Powerwall 2 was designed to allow for flexible operations with over-the-air updates that can push new functionality down to the Powerwall. The internet connectivity of the Powerwall Backup Gateway 2 allows it to stay connected to the internet to keep tabs on changing electricity prices, energy policies, and even the weather. These data are rolled together into a package that is constantly working to optimize the energy footprint of the home using a handful of optimization features.

Time-Based Control. A Smart Way to Use Energy.
If your utility prices vary throughout the day, set Powerwall in Time-Based Control to maximize savings. Powerwall learns patterns in your energy usage and solar generation-- using stored energy to avoid purchasing high-cost electricity.

The Tesla Powerwall has the ability to maximize the self-consumption of an onsite solar system. This is accomplished by storing up power during the day and using that stored power as needed to power the home. Tesla estimates that the ability to store daytime solar generation and use it back from the battery at night roughly doubles the amount of solar energy that directly powers your home.

As a residential battery, one of the primary functions of the Powerwall is to provide backup power in the event of a utility power outage. In the event that the outage lasts for an extended period, Powerwall can actually recharge itself from a rooftop solar power system. That capability means that while your neighbors might be without power for hours, days, or even weeks, a solar-connected Powerwall system can effectively keep your home powered indefinitely, within the constraints of the size of the solar system and the number of Powerwalls installed, of course.

Powerwall is connected to the internet and work to optimize the cost of energy for customers with electricity rates that vary depending on the time of day or the season. With Advanced Time-Based Control, Powerwall actively works to maximize the value of the solar generation and the energy usage of the home from the grid to intelligently charge and discharge based on the time and price of energy.

When connected to an onsite solar power system, Advanced Time-Based Control can operate in either a balanced mode or a cost saving mode. Balanced mode prioritizes using stored solar power to power the home when electricity is expensive and after the sun goes down. Cost-saving mode, on the other hand, optimizes the storage and usage of electricity to make the overall usage profile of the home as low cost as possible, maximizing savings that come as a result of having residential energy storage.

The Tesla Powerwall 2 has a handful of special modes of operation that solve for some of the more unique use cases. Those currently include Grid Services, Storm Watch, and Preconditioning, but more may be added with over-the-air updates in the future.

Grid Services — Powerwall customers participating in Grid Services programs now know when their systems are benefiting the grid and can track Grid Services energy and power usage.

Storm Watch — Storm Watch automatically detect incoming storms and prepare for them by keeping energy stored in the Powerwall. For Powerwall customers with backup and in selected regions, Tesla will automatically detect incoming storms and charge the Powerwall up completely to ensure power is available in the event of a weather-related grid outage.

Preconditioning — The Tesla Powerwall 2 is the only residential battery system on the market today that offers a full liquid thermal management system, according to Tesla. That translates to a completely sealed, liquid coolant system that circulates the 2.3 L (2.4 quarts) of liquid coolant in Powerwall throughout the battery array to ensure they are operating at the ideal temperature.

This integrated thermal management positions the Powerwall 2 uniquely in the market with its ability to operate at the widest range of temperatures compared to the competition, functioning from -4°F to 122°F.

The Tesla Powerwall can be managed from the Tesla mobile app, which is available in the Android and iOS app stores. This is the same app that Tesla vehicle owners use to monitor their vehicles, check on the status of vehicle charging, and check or conduct other vehicle functions. After logging into your Tesla account in the app, you can see the current state of charge of the Powerwall and change Powerwall settings.

On the energy side of things, the Tesla mobile app allows owners to monitor the energy flow between their rooftop solar systems, Powerwalls, the grid, and the energy usage of their homes. The realtime flow of energy is depicted with vivid graphics that make it easy to see where energy is flowing and how much is flowing.

More details can be found on the Powerwall website.