German IT services firm GISA is using the waste heat from its data center to heat its offices.

The company announced it is now using the waste heat from its own data center to preheat rooms at its Halle site outside Leipzig.

The heating solution is used during the colder months of the year. The data center’s cooling water returns at approximately 21°C and is coupled with the room air circulation system which ensures that the significantly cooler outside air flowing into the rooms can be heated.

This allows the offices to be preheated to approximately 20°C with minimal additional heating. In the summer, a dedicated chiller continues to cool the room air.

The company said the site’s energy consumption was reduced by approximately 22,000kWh in January 2025 alone.

GISA is an IT service provider based in Halle (Saale) formed in 1993 from the IT departments of Mitteldeutsche Energieversorgung, together with Stadtwerke Halle, Erdgasversorgung Westsachsen, and Gasversorgung Sachsen-Anhalt. Today the company is owned by NTT Data (via NTT Data Business Solutions AG), energy firm EnviaM, and Municipal Economy Saxony-Anhalt.

Specifications of the data center haven’t been shared.

GISA CEO Heino Feige said: “Data centers are often underestimated as heat sources, but they offer enormous potential. We are proud that we can now reuse waste heat as a valuable byproduct. This gives us the opportunity to use existing resources even more efficiently and make a contribution to climate protection – definitely an issue that is close to our hearts at GISA and anchored as a top strategic goal.”

The recently introduced German Energy Efficiency Act requires heat recovery for new data centers, but GISA noted it is not mandated for existing facilities.