Actually, technology can disappear even sooner than when the net energy from fossil fuels becomes negative. The economy needs a growing (net) energy supply to continue to grow. Perhaps efficiency and technology changes can change this relationship slightly, but this is approximately the situation.
So instead of the Second Law of Thermodynamics being what brings about the end of technology, it may by Roddier’s Third Law of Thermodynamics that brings about collapse and the end of technology, even though some net energy might theoretically be available, if debt could rise endlessly. - Gail Tverberg