Data centers with renewable energy

Picture energy efficient data centers

We at Deutsche Telekom rely on the use of green technologies, so-called Green IT. This makes a considerable contribution to counteracting climate change. In addition to this, we can offer customers environmentally friendly and energy-efficient solutions.

Picture using green power

Since 2008, Telekom has been obtaining 100% of the power it uses in Germany from renewable energy sources, some of which are RECS-certified. As a result of the Telekom Housing Services’ integrated IT and facility management, we can offer ecologically sustainable services. With the green energy supply at our IT premises, we are working to avoid CO2 emissions as much as possible and to provide CO2-neutral data centers
The sustainable use of green power also contributes to cost savings. Power consumption in the data center can be further reduced, and valuable resources conserved, making the energy-efficient data center a reality.

Technical facts regarding our data centers:

Air conditioning compliant with ASHRAE

For our new T-rack, we have designed the air conditioning systems in compliance with the new ASHRAE 2011/A2 standard. The ASHRAE 2011/A2 climate model enables a warmer or colder, dryer or more humid environment in data centers, without damaging the IT.
ASHRAE 2011 recommends a server supply-air temperature between 18°C and 27°C (marked in dark blue in the graphic below).
For of our T-racks, we have an average supply-air temperature of between 25°C and 27°C. ASHRAE is divided into various classes. The permitted range for the respective classes extends well above these values. In the ASHRAE 2011/A2 climate model, the permitted temperature range is from 10°C to 35°C (marked in light blue in the graphic below).

Picture air-conditioning in accordance with ASHRAE

The air humidity is also taken into account within a climate model, and the humidity in the rooms must not exceed or fall short of the permitted range. For ASHRAE 2011/A2, it must be between 20% and 80%. For comparison: In living rooms the air humidity is generally between 40% and 60%.
For T-racks, then, it is necessary to ensure the use of servers that comply with these requirements.

Climate classes 3K1 and 3K2

In our data centers, we focus on climate classes 3K1 and 3K2. Depending on requirements, there are various air-conditioned rooms available to you at different properties.

3K1 climate model: 

  • Server inlet temperature: 20°–25°C, deviation limit 2°C
  • Relative humidity: 20–75%
  • Rate of temperature change: 0.1°C/min. (averaged over a period of 5 min.)

3K2 climate model:

  • Server inlet temperature: 15°–30°C, deviation limit 2°C
  • Relative humidity: 10–75%
  • Rate of temperature change: 0.5°C/min. (averaged over a period of 5 min.)

In both climate classes, the supply-air is generally regulated via a raised floor, while the extracted air is suctioned off in the ceiling area. This is clarified in the graphic below.

Picture climate model

PUE Value

The PUE value is calculated by dividing the total consumption of the data center by the total consumption of the IT equipment (server, storage systems, and network hardware). Here, the result cannot be lower than the theoretical value 1.0, and should not exceed 2.0. A theoretical value of 1.0 means that the infrastructure systems (cooling, etc.) have zero consumption, which is not possible in practice. A highly efficient, cutting edge data center achieves a PUE value of 1.2–1.3.

Total data center consumption [kWh]


PUE value (consumption of the infrastructure systems)
Total consumption of IT equipment [kWh]



Jörn Krinelke
Jörg Pfeffer