Background: Japan experiences frequent earthquakes and typhoons. The government encourages households to install energy storage as disaster preparedness equipment. Tokyo Electric Power Company (TEPCO) implements time-of-use electricity tariffs.

User Profile: A three-person household living in a detached single-family home, with an existing 5kW PV system installed.

Pain Point: The family experienced a 24-hour power outage that left them unable to charge devices, power lighting, or refrigerate medication. They also wish to reduce electricity bills through peak-valley price differences.

Solution:

• 1、Configuration: 8kWh wall-mounted residential energy storage + dedicated disaster preparedness power outlets

• 2、Strategy: Charge during off-peak nighttime hours and discharge during peak daytime hours. At the same time, reserve 20% of battery capacity for disaster preparedness backup.

Results:

• 1、Disaster backup power can sustain refrigerator, lighting, and communication equipment for 10–12 hours

• 2、Peak-valley arbitrage saves approximately ¥80,000 per year in electricity costs

• 3、Receives local government disaster preparedness subsidies (covering 30% of system cost)