The Hessian State Agency for Nature Conservation, Environment and Geology has been collecting temperature data of the subsurface up to about 200 m for about 20 years. Many of these temperature data were collected in connection with thermal response tests. The experience gained by HLNUG in its own temperature profile measurements in borehole heat exchangers (borehole heat exchangers) over the last 5 years shows that the temperatures measured in borehole heat exchangers depend on various parameters, in particular the time of measurement. ...