We give a brief review of quantum energy inequalities (QEIs) and then discuss
two lines of work which suggest that QEIs are closely related to various
natural properties of quantum field theory which may all be regarded as
stability conditions. The first is based on joint work with Verch, and draws
connections between microscopic stability (microlocal spectrum condition),
mesoscopic stability (QEIs) and macroscopic stability (passivity). The second
direction considers QEIs for a countable number of massive scalar fields, and
links the existence and scaling properties of QEIs to the spectrum of masses.
The upshot is that the existence of a suitable QEI with polynomial scaling is a
sufficient condition for the model to satisfy the Buchholz--Wichmann nuclearity
criterion. We briefly discuss on-going work with Ojima and Porrmann which seeks
to gain a deeper understanding of this relationship.