AI has put data center electricity use in the news. What is less well known is that almost all of that electricity ends up as heat.
Just as a laptop gets hot after long use, servers give off heat in proportion to the electricity they use, and almost all the electricity a data center uses turns into heat this way. The data center has to cool its servers and release that heat outside. This post looks at why data centers produce waste heat, how much they produce, and how the cooling method shapes the heat that comes out.
Data center power use
According to the International Energy Agency (IEA), servers use about 60% of a data center’s electricity, with storage taking around 5% and network equipment up to 5%. Much of the rest goes to cooling: about 7% in efficient hyperscale data centers, and more than 30% in less efficient enterprise ones.
The electricity servers use turns almost entirely into heat. If that heat is not removed the servers overheat, so a data center has to cool them around the clock. Today, most of the heat removed this way is simply released outside.
How much waste heat data centers produce
| Data center electricity use | |
|---|---|
| World (2024) | About 415TWh, about 1.5% of global electricity use |
| World (2030 projection) | About 945TWh, more than double |
| South Korea (2023) | About 5TWh |
| South Korea (2040 projection) | About 31.6TWh, more than six times |
Since the electricity comes back out almost entirely as heat, the more power data centers use, the more heat they throw away.
Data center cooling and waste heat temperature
There is a lot of this heat, but it is not very hot, and its temperature depends on how the servers are cooled.
- Air cooling: Most data centers today blow cold air between the servers. The air that leaves is barely warmer than the surroundings, so its heat is hard to reuse.
- Liquid cooling: Water flows directly over the server chips to carry heat away. The water comes out at 45–70°C, which is far easier to reuse. AI servers produce a lot of heat, so liquid cooling is spreading quickly as AI grows.
The bottom line
Almost all the electricity a data center uses becomes heat, and as power use grows, so does the heat thrown away. That heat is low in temperature, though, and how reusable it is depends on how the servers are cooled. As liquid cooling spreads, data center heat is turning from heat to get rid of into heat that can be used.
If you are wondering where this discarded data center heat can be used, the next post is a light read.
Sources
- Energy and AI: Energy demand from AI — International Energy Agency (IEA) (2025-04) — servers about 60%, storage about 5%, network up to 5%, cooling about 7% (hyperscale) to over 30% (enterprise), about 415TWh in 2024 (about 1.5% of global electricity), about 945TWh in 2030
- Implications of Data Center Growth in the AI Era for Korea’s Energy Consumption — Korea Energy Economics Institute (KEEI), Basic Research Report 2025-09 (2025-12-31, in Korean) — baseline outlook, South Korean data center electricity demand 5.0TWh in 2023, 31.6TWh in 2040
- Heat Reuse, Data Center Roadmap — Innovation for Cool Earth Forum (ICEF) (2025) — almost all data center electricity becomes heat, air-cooled exhaust is close to ambient temperature and hard to reuse, liquid cooling recovers heat at 45–70°C, GPU-based AI is driving rapid growth in liquid cooling
- Cover image: AI-generated (colour-adjusted)