A new website for children, ClimateCops.com, is among several features created for the initiative, while npower is also offering free audits and advice to educational establishments.
Mr Duff said: "The npower Greener Schools programme underlines our commitment to protecting the future of UK schools and the environment.
"Our aim is to make children feel empowered to make a difference and guarantee a brighter future."
npower is one of the UK's leading gas and electricity suppliers, with nearly seven million household and business customers across Britain.
The company also supplies green energy to both Wembley Stadium and the Millennium Stadium, and was recently awarded platinum status in Business in the Community's CR index.
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