A energy specialist from the World Bank addressed the 25th Pacific Power Association Conference in Nuku'alofa.
Kamleshwar Khelawan said about 7 million people in the Pacific didn't have access to electricity meaning only about 20% of households did.
Mr Khelawan said significant investment was needed in the energy sector but private investment had not been encouraged.
Matangi Tonga reported him as saying all Pacific Islands faced similar challenges in providing sustainable energy.
He said the energy sector was characterised by weak, outdated legislative and institutional arrangements which were often ambiguous.
In terms of renewable energy resources, he said there was hydropower and geothermal potential in a number of countries, while solar and wind remained the main options with biofuel as another option.
But the energy specialist said governments alone could not pay for this and a combination of government, private sector and development partners' efforts was required.