Black holes actually green: official

Scientists studying the energy output of black holes have discovered to their surprise that "the conversion of energy by matter falling toward a black hole is much more efficient than nuclear or fossil fuels" - so much so that "if a car was as fuel-efficient as these black holes, it could theoretically travel more than a billion miles on a gallon of gas".

That’s according to boffins at the Chandra X-Ray Observatory, who studied the inner regions of nine elliptical galaxies with a view to determining the rate at which gas is being sucked towards said galaxies’ supermassive black holes.

The Register