US DOE estimates 20–50% of industrial energy input is ultimately rejected as waste heat; a large share of the medium- and low-grade portion is technically recoverable.
From our guide: Heat Recovery Systems for Industry — full context, charts and sources there.
Boilers, kilns, heat exchangers, valves and steam lines lose energy continuously. Inzonex makes patented (UK GB2508992.1) removable modular insulation — snap-fastened covers engineered per temperature tier, not generic off-the-shelf jackets: