Floss and Dietrich (Optimierte integration von Pufferspeichern in hydraulische Systeme, in:Proceedings of the International Congress e-nova 2008, Pinkafeld, Austria, 2008, pp. 129–136, ISBN 978-3-9500919-8-4) points out that due to different effects such as mixing or heat conduction inside the tank,the supply temperature at the consumer is lower than the outlet temperature of the heat pump.