global investment in energy enduse technologies was more than double the supplyside investments and reached an estimated trillion in of which almost trillion was for road vehicles griibler and others forthcoming other private sector investments in energy technology include investment by angel investors companies internal investments debt instruments project finance mergers and acquisitions and investments in publicly listed energy technology firms energyrelated venture capital investments boomed in eu and north america in recent years reaching billion or per cent of all private investments in energy technology diffusion in international energy agency