The UN Development Program and World Health Organization described in a recent report 2 billion people as lacking natural gas, propane or other modern fuels used for cooking or heating their homes, and said 1.2 billion more people live entirely without electricity.
The report, done with the collaboration by the International Energy Agency, cited the lack of energy access as a health factor for many of the world's 6.7 billion in population, particularly for the world's poorest living in the least developed nations of South Asia and sub-Saharan Africa.
"Almost half of humanity is completely disconnected from the debate on how to drive human progress with less emissions and greener energy, because their reality is much more basic than that," said Olav Kjorven, head of policy development for UN Development Program.
"They carry heavy loads of water and food on their backs because they don't have transport," he said.
"They cook over wood fires that damage their health, not with electricity, gas or oil. We must ensure that the energy needs of these people are central to a new climate agreement."
Kjorven and energy and health officials said poor people must have access to those modern fuels and to electricity produced by a mixture of traditional but clean-burning technologies, but also by more renewable sources of energy.
According to the report, 2 million people a year die from causes associated with exposure to smoke from cooking with dung and other biomass or with coal, and all but 1 percent of those deaths occur in developing countries.
It said half of all deaths from pneumonia in children under five years and from chronic lung disease and lung cancer in adults are attributed to solid fuel use, compared with 38 percent in developing countries.
Fatih Birol, Paris-based IEA's chief economist, said he hopes for "a strong signal sent from Copenhagen to the energy sector to kickoff this transformation."
The negotiating conference in Copenhagen in December is aimed at forging a comprehensive new accord to combat climate change, but an interim agreement is appearing more and more likely, with many of the details to be filled in next year.
The agreement would replace the 1997 Kyoto Protocol for cutting industrialized countries' emissions of carbon dioxide and other heat-trapping gases when it expires at the end of 2012.