  Quantum work is usually determined from two projective measurements of the
energy at the beginning and at the end of a thermodynamic process. However,
this paradigm cannot be considered thermodynamically consistent as it does not
account for the thermodynamic cost of these measurements. To remedy this
conceptual inconsistency we introduce a novel paradigm that relies only on the
expected change of the average energy given the initial energy eigenbasis. In
particular, we completely omit quantum measurements in the definition of
quantum work, and hence quantum work is identified as a thermodynamic quantity
of only the system. As main results we derive a modified quantum Jarzynski
equality and a sharpened maximum work theorem in terms of the information free
energy. Comparison of our results with the standard approach allows to quantify
the informational cost of projective measurements.
