The country’s first office building fully powered by off-the-grid solar energy opened Monday in the city of Saga.

Daiwa House Industry Co. is promoting the two-story, 2,400-square-meter facility as a “net-zero energy building” that offsets primary energy consumption through the use of renewable energy created on the site.

The building will serve as the homebuilder’s Saga branch office as well as demonstrating the type of environmentally friendly office buildings the firm can construct for other companies.

Electricity generated by 320 solar panels on the roof is stored in lithium-ion batteries, which then supply power to keep the building functioning through the night.

The building boasts energy-saving equipment such as an air conditioning system utilizing solar heat and water in a well, which saves about ¥6 million a year in electricity costs compared with a conventional facility of the same size.

A local utility will supply electricity to the building only when it is unable to generate enough power on its own, for instance during a prolonged spell of bad weather.

The total construction cost came in at about ¥900 million, which was partially funded by government subsidies.

“We want to promote our environmental technology as public awareness of energy-saving has been rising,” a Daiwa House official said.