The Ministry of Economy, Trade and Industry will expedite the use of "electric power storage batteries" charged at night to prevent daytime power shortages, METI officials said Thursday.

Electric power storage batteries, such as sodium-sulfur and REDOX Flow batteries, are charged during off-peak hours for use in the daytime when demand peaks.

The ministry will consider subsidizing firms who invest in the costly battery facilities to help limit the daily load on power companies, they said.

Several types of storage batteries have been commercialized, and power utilities have been selling them schools and factories.

But the high cost of the batteries has been hampering wider use.

Office building operators with contracts for consuming up to 1,000 kilowatts would have to spend 200 million yen on average to set up batteries with comparable power.