San Diego, CA — In the past, a PV system with battery storage was associated with the off-grid system — not connected to the utility grid. The battery stores the energy produced by the PV system and when the sun goes down, electricity is drawn from the battery. In Japan, the battery became attractive to store electricity from “the grid,” to reduce electricity bills.
After the devastation of the Tsunami and nuclear meltdown in Mach 2011, Japan became painfully aware of the importance of both safety and maintaining a steady supply of electricity. The combination of a PV system and battery storage gives consumers the ability to produce, store and supply electricity throughout the day at their own home for power outages and emergencies. However, the system can bring economic benefits — electricity bill reduction — during normal days.
Like California, utilities in Japan offer Time-of Use (TOU) rates. How homeowners can reduce electricity bills can be illustrated by using Tokyo Electric Power Company’s (TEPCO) current (non-summer) TOU rates for all-electric homes with a PV system.
- Purchase and store electricity from the grid at off-peak hour (11 pm – 7 am) at ¥11.82/kWh [US $0.12]
- Sell PV-generated electricity to the utility at the FIT premium rate of ¥38.0/kWh [US $0.38]
- Use PV-generated electricity during day time, otherwise paying at ¥30.77 (10 am – 5 pm) [US $0.31] and use stored electricity between 7 and 10 am and between 5 and 11 pm, otherwise paying ¥25.2/kWh [US $0.25]
With the battery storage, PV homeowners can ultimately buy electricity at the lowest rate (¥11.82/kWh or $0.12/kWh) and sell at the highest price (¥38/kWh or $0.38/kWh).
The key domestic PV makers, Panasonic, Kyocera and Sharp, all now offer lithium-ion battery storage along with a PV home system to meet consumers’ demand. Their goal is to move beyond PV and expand into a total Home Energy Management System (HEMS3) arena.
Kyocera started offering PV plus lithium-ion battery storage to homeowners in early 2012 with a target of selling 10,000 units from April 2012 to March 2013. Panasonic also released home battery storage systems that can be connected to Sanyo’s (now Panasonic) HIT PV system. The battery has a capacity of 4.65 kWh and is priced at ¥1.218 million MSRP [US $11,984].
In April, Kyocera released the largest residential lithium-ion battery in Japan. The battery has the capacity of 14.4 kWh, which is priced at an MSRP of ¥4.45million [US $43,784]. This large capacity allows it to power a home refrigerator, TV, computers, lights and cell phone chargers for up to 24 hours.
Kyocera has teamed up with Rakuten, Inc., which operates the nation’s largest internet shopping site, to offer a PV system (poly-Si) and a lithium battery (7.2 kWh) set for homeowners at an affordable price. Rakuten provides options with different sizes of PV systems with the battery, and installed system price (after tax) varies from ¥2.94 million ($29,730) with a-2.28 kW system to ¥4.168 million ($42,153) with a 6.27-kW system. These systems are installed by one of the nation’s largest installers, Nippon Ecosystem, which is part of Itochu Corp.
Residential battery systems remain expensive to average homeowners. To solve this issue, One Energy Corp. has just begun the nation’s first residential energy storage leasing service. Like SolarCity or SunRun’s PV leasing service in the U.S., this requires zero upfront payment to homeowners. The company is a joint venture between Orix, NEC and Epco. NEC provides lithium batteries, whose technology is used for Nissan Leaf electric vehicles.
Besides the energy storage leasing service, One Energy also offers “Yanekari (PV rooftop space leasing)” service. A homeowner can lease a storage system with 5.53 kWh of capacity at between ¥3,045 ($31) to ¥5,145 ($52) a month from One Energy while offering the roof-space to One Energy, making a monthly revenue of ¥2,500 ($25). The image below illustrates how a customer could use an energy storage system to offset the high cost of purchasing energy during peak times.
One Energy currently offers this leasing service in the TEPCO region only and is planning to expand to the Kansai region by the second half of this fiscal year and eventually expand nationwide.
NEC started mass production of residential storage systems in February. Besides partnering with One Energy, the company sells home batteries directly to homebuilders and building material distributors with the goal of selling 15,000 units during this fiscal year.
The company stated that PV homeowners will start storing PV electricity in batteries even more as the FIT rate gets lower in the future, creating a more self-sufficient and less grid-dependent environment.
It is declining, but the national government provides upfront, capacity-based rebates (¥15-20/kW) and a net FIT of ¥38/kWh on excess electricity generation for 10 years) for PV home systems. The government also currently provides a subsidy for lithium-ion battery storage for homeowners. The subsidy is one third of the installed system cost or up to ¥1 million ($10,823).
The hot and humid summer is approaching in Japan. Some of the nation’s utilities have just raised electricity rates and many of them will request that consumers limit and/or shift electricity consumption from peak to off-peak to control raising fossil fuel cost caused by the shutdown of nuclear power plants. With PV + battery systems, homeowners are moving to take energy matters into their own hands in defense against rolling blackouts and rising electricity bills.
Lead image: House with light via Shutterstock