Tokyo Electric Power Co. returned to profit in the fourth quarter, as lower energy prices helped offset a weaker yen and one-off gains boosted net income.

Tepco, the country's biggest power utility, posted operating profit of ¥17.3 billion ($145 million) in the three months ended March 31, rebounding from an operating loss of ¥40 billion a year earlier, according to Bloomberg calculations based on full-year results released Tuesday.

Full-year operating profit of ¥316.5 billion fell short of expectations and the company said it couldn't give profit or sales forecasts for the year while the restart of nuclear power in Japan remains uncertain.

The operator of the wrecked Fukushima No. 1 plant said full-year net income was ¥451.5 billion, up 2.9 percent on the year and benefiting from net gains in government payments to the company that will be disbursed as compensation for the Fukushima disaster.

A more than 50 percent plunge in crude oil prices last year has helped Japanese utilities offset the impact of a weaker yen that makes imports more expensive. Tokyo Electric, or Tepco, has also embarked on a cost-cutting campaign to help rein in operating expenses.

Japan's regional power utilities have endured several years of mounting losses after turning off nuclear power since the Fukushima disaster began in March 2011. All of Japan's operable reactors remain shuttered pending safety reviews and approvals.