This paper compares five methods to calculate CO2 intensity (g/kWh) of power generation, based on different ways to take into account combined heat and power generation. It was found that the method chosen can have a large impact on the CO2 intensity for countries with relatively large amounts of combined heat and power plants. Of the analysed countries, the difference in CO2 intensities is found to be especially large for Russia, Germany and Italy (82%, 31% and 20% differences in 2007, respectively, for CO2 intensity of total power generation). This study furthermore shows that by taking into account transmission and distribution losses and auxiliary power use, CO2 intensity for electricity consumption is 8-44% higher for the analysed countries than the CO2 intensity for electricity generation, with 15% as global average, in 2007. CO2 emissions from power generation can be reduced by implementing best practice technology for fossil power generation. This paper estimates a potential of 18-44% savings, with 29% as global average. An additional potential is expected to exist for reducing transmission and distribution losses, which range from 4% to 25% of power generation in 2006, for the analysed countries, with 9% as global average. (C) 2010 Elsevier Ltd. All rights reserved.