The MiEV power BOX will cost 149,800 (£1,160) when it goes on sale through dealers in April, and MMC said a fully charged battery can supply 1,500 watts of power for between five and six hours, equivalent to a single day of power usage for an average Japanese household.

Japan is only too aware of the potential for blackouts. MMC said last year it was considering the device after the car was used for energy supply following the Japanese tsunami. In January, Toyota supplied 17 similar units to earthquake-hit Miyagi Prefecture, allowing users draw to draw energy from the Prius hybrid’s battery. The feature will be factory-fitted to all Japanese-market models from this year.