The program will be undertaken mainly by subsidiary NTT Anode Energy Corp., which was established in June, sources said.
The major telecommunications company will spend about ¥100 billion annually from fiscal 2020 during the six-year period while promoting cooperation with electric power companies, the sources said.
NTT will install lithium-ion storage batteries in buildings owned by the company across Japan. Electricity produced by the battery systems will be provided to nearby facilities, such as hospitals and factories, in the event of power outages caused by disasters or other emergencies.
The company will also promote the construction of solar and wind power generation facilities, with electricity from the facilities to be sold through Ennet Corp., another NTT subsidiary, the sources said.
Through the fresh investment, NTT aims to double annual revenue from its electricity business to about ¥600 billion in fiscal 2025 from some ¥300 billion at present, the sources said.
The NTT group is expanding its electricity operations at a time when growth of its mainstay mobile phone business is seen decelerating.