Japanese solar project developer Sun Village has announced the grid connection of a solar-plus-storage facility with a DC/AC oversizing ratio of 327% at an undisclosed location in Japan.
Described by the company as a “low-voltage, super-oversized” solar power plant with battery storage, the facility features 163.2 kW of installed PV capacity, a 253.3 kWh battery storage system and a 49.9 kW power conversion system (PCS).
In Japan, low-voltage solar projects typically have an AC output of less than 50 kW, while super-oversizing refers to installing PV capacity substantially above the rated output of the PCS. This configuration allows developers to increase electricity generation without expanding grid connection capacity.
Super-oversizing differs from conventional oversizing in its significantly higher ratio of installed PV capacity to inverter output, often exceeding 300%. By comparison, the average oversizing ratio for solar installations with capacities between 10 kW and 50 kW commissioned in Japan in 2024 was approximately 180.5%, according to the Ministry of Economy, Trade and Industry (METI).
“The plant is expected to sell approximately 222,000 kWh of electricity annually,” Sun Village said in a statement. “The DC-coupled configuration allows surplus electricity that would otherwise be curtailed during peak daytime production to be stored in the batteries and sold in the evening and at night, when solar generation declines.”
According to the company’s simulations, the system is expected to maintain a stable electricity output of 49.9 kW for approximately 14 hours. Under Japan’s feed-in premium (FIP) scheme, Sun Village will act as an aggregator, handling generation forecasts, power generation planning and battery operations, while selling electricity on the wholesale electricity market.
Such configurations could gain traction in Japan as developers seek to maximize generation from existing grid connections amid constraints on available grid capacity and rising interconnection costs. Combining heavily oversized PV arrays with battery storage could allow operators to capture electricity that would otherwise be lost through inverter clipping, while extending electricity exports beyond daylight hours.
Japan’s gradual shift from fixed feed-in tariffs to market-linked remuneration under the FIP scheme could also support wider adoption of solar-plus-storage projects. By storing electricity during periods of high solar output and selling it when wholesale prices are higher, developers could improve project revenues and reduce exposure to low midday electricity prices. However, the economic viability of super-oversized systems will depend on battery costs, electricity price spreads and the amount of otherwise curtailed generation that can be recovered.
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