Direct measurements of heat emissions from air-conditioning systems into the urban atmosphere – New publication in Urban Climate

Anthropogenic heat flux is a key component of the urban energy balance. In this recent study, direct in-situ measurements of waste heat from air-conditioning systems were carried out for the first time. The measurements took place in the summer of 2025 at a university building belonging to the Technical University of Braunschweig. It was found that not only air temperature but also humidity plays an important role in the heat emission from air-conditioning systems. The sensible heat flux increased by approximately 3.6–4.5 W/m² per 1 K rise in air temperature and by around 4.3 W/m² per 1 hPa rise in vapour pressure. The study enables the evaluation of urban climate models and forms the basis for further studies on anthropogenic heat emissions from air-conditioning systems.

Heyen, M., Heusinger, J., Weber, S., 2026. Anthropogenic heat flux from air-conditioning: direct measurements and meteorological controls. Urban Climate 69, 103101. https://doi.org/10.1016/j.uclim.2026.103101