The electric and gas company, whose regulated operations serve 7.2 million customers in the Southeastern and Midwestern US, proved to be a top performer across the economic, environmental and social dimensions platforms.

The DJSI assesses industry-specific topics including corporate governance, environmental policy, climate strategy, human capital development and labour practices.

In announcing the gong for Duke, the DJSI noted the company’s $US9 billion ($A9.9 billion) generation fleet modernisation program, whereby Duke retired about 3830 megawatts of older coal-fired units.

It will grow to nearly 6300MW of coal capacity retired over the next few years – about a quarter of the company’s earlier coal fleet.

The fleet modernisation and environmental controls investments have helped reduce sulphur dioxide emissions by 84% and nitrogen oxide emissions by 63% since 2005.

The DJSI also noted Duke’s new sustainability goal focused on ash management, which includes the development of a long-term strategy to manage the closure of coal ash basins across the Duke Energy system.

Duke said it was on track to meeting its goal of owning or purchasing 6000MW of wind, solar and biomass energy by 2020.

Additionally, Duke Energy companies have distributed nearly 46 million energy-efficient light bulbs to customers since 2009, helping them save enough energy to power nearly 144,000 homes and offset the carbon output of 266,000 passenger cars.

In 2013, Duke Energy recycled 25,719 inefficient refrigerators and freezers through its appliance recycling programs.

Almost 26 million kilowatt-hours of energy were saved last year – enough to power nearly 2100 homes.

S&G Dow Jones and Zurich-based RobecoSAM have compiled the index since 1999.