Energy intensity is a measure of the energy efficiency of a nation's economy. It is calculated as units of energy per unit of GDP.1  High energy intensities indicate a high price or cost of converting energy into GDP. 2  Low energy intensity indicates a lower price or cost of converting energy into GDP.t is calculated as units of energy per unit of GDP. 1  High energy intensities indicate a high price or cost of converting energy into GDP. 2  Low energy intensity indicates a lower price or cost of converting energy into GDP.