How much industrial energy is lost as waste heat?

The U.S. Department of Energy puts it at roughly 20–50% of industrial energy input. In Korea, the Korea Energy Economics Institute estimates 6.4 million TOE a year from energy-intensive manufacturers in industrial complexes — an average of 13.7% of their final energy consumption.

Why is low-grade waste heat so hard to recover?

Below about 100°C, the heat is too cool to feed straight back into most processes. Add a mismatch between when the heat appears and when it is needed, or a long distance to the nearest user, and it cools off before it can be used.

What Is Industrial Waste Heat? Sources and Scale

Q: What is industrial waste heat?

It is the energy that leaves a plant as heat rather than as product, when fuel or electricity is used to heat, melt, or dry something. The three main escape routes are flue gas going up the stack, cooling water warmed by the process, and the hot surfaces of equipment and product.

A factory is not only a place that consumes energy; it also throws an enormous amount of it away. Every time fuel is burned or electricity is drawn to heat, melt, or dry something, a large share of that input leaves as heat rather than as product. That unused heat is what we call industrial waste heat.

Where industrial waste heat comes from

Industrial waste heat is the heat left over once a process has done its job — or the heat that never made it into the job at all. It leaves the plant along three main routes.

The three routes by which industrial waste heat leaves a plant: exhaust gas up the stack, cooling water warmed by the process, and the surfaces of hot equipment and products

How much is wasted

Three figures on the scale of industrial waste heat: 20–50% of industrial energy input, 6.4 million TOE a year from Korean industrial complexes, about twice the heat Korea's district heating uses in a year

The U.S. Department of Energy estimates that roughly 20–50% of the energy fed into industry is lost as waste heat. In Korea, the Korea Energy Economics Institute produced the first national estimate in 2023: 6.4 million TOE a year from industrial complexes alone, about twice the heat the country’s district heating uses in a year. Low-grade heat around 100°C, in particular, is hard to feed back into a process, and most of it is simply discarded.

Why it has gone unrecovered

The three barriers that kept waste heat from being recovered, and their answers: temperature with a heat pump, timing with storage, distance by storing and carrying the heat

Three barriers explain why so much of this heat is still thrown away: it is cooler than the process needs, it comes out when nothing needs it, or the nearest user is so far away that it cools off in transit. Each has an answer — lift the temperature with a heat pump, bridge the timing with storage, and cover the distance by storing the heat and carrying it.

The bottom line

Waste heat is energy the plant has already produced, so every unit put back to work is fuel that does not need to be burned. The question is not whether the heat is there, but whether it can be used at the temperature and the time it is needed.

IsoTES® is GIGAette’s constant-temperature thermal storage system, designed to hold waste heat and release it at the same temperature when it is needed.

If you want to look at what your own plant is losing, request a technical meeting.

For how factories actually put waste heat to use, see:

How Factories Use Waste Heat: 6 Common Methods

Industrial waste heat goes into preheating, steam, district heating, heat pumps, power and cooling. What each of the six common methods produces and which waste heat it suits.

Sources

Park, S. and Oh, S., Analysis of Heat Consumption Characteristics in Industrial Complexes and Estimation of Waste Heat Potential, Korea Energy Economics Institute, Basic Research Report 23-11 (summarised in Issue Paper 24-11) — 6.4 million TOE of waste heat a year, averaging 13.7% of final energy consumption; about twice district heating consumption (2.8 million TOE)
U.S. Department of Energy, “Waste Heat Recovery Basics” — 20–50% of industrial energy input lost as waste heat via exhaust gas, cooling water, and hot equipment and product surfaces