NARAHA, Fukushima Prefecture--In a blow to a region hit hard by the Fukushima nuclear disaster, offshore floating wind turbines being operated on a trial basis here are producing much less electricity than initially anticipated.

The disappointing output so far is casting a shadow over the government-backed project.

While the capacity factor--the ratio of the actual electricity output to the maximum possible output--should be around 30 percent for new windmills, only one of the three turbines tested in the program affiliated with the Ministry of Economy, Trade and Industry has reached the standard.

That means whether the offshore floating turbines can be commercialized remains unclear.

Backed by the ministry, the trial was started by a consortium comprising trading house Marubeni Corp., Mitsubishi Heavy Industries Ltd. and other companies in fiscal 2011.

Three windmills with a capacity of 2, 5 and 7 megawatts, respectively, along with an electrical substation, were built in waters 20 kilometers off Naraha at a cost of 58.5 billion yen ($527 million).

The largest of the three is one of the biggest windmills in the world. It measures nearly 200 meters from the water surface to the tip of the blade and can reportedly provide power to 6,000 households.

The wind turbines were expected to be put into practical use in the near future to help the region devastated by the 2011 accident at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear plant recover from the disaster.

The ministry said although the capacity factor for the 2-megawatt windmill was 34 percent over the past two years, slightly higher than the 30-percent goal, the figure for the 5-megawatt turbine, whose operations started in February last year, was just 12 percent.

A capacity factor of 2 percent, far below the target, was reported for the largest, 7-megawatt turbine.

Asked why the figure for the biggest windmill was so low, the ministry cited “defects of the world’s first hydraulic gearbox installed in it and other parts” as the reason.

The ministry said it has not decided on the future of the windmills.

“The results of the trial should be examined first of all,” said a ministry official.

The joint entity shows a cautious stance toward making the offshore turbines available for commercial use, arguing whether to commercialize them will be decided based on their profitability.

In a separate effort, Tokyo-based construction firm Toda Corp. introduced an offshore floating wind power-generating facility with an output of 2 megawatts in fiscal 2016 off Goto, Nagasaki Prefecture, on a commercial basis.

Plans have been made to install an additional nine turbines with a total capacity of 22 megawatts and an environmental assessment is being carried out there.