Abstract When a liquid starts to solidify only when cooled well below its melting temperature, this is called subcooling. From nucleation theory, subcooling is expected to increase for small volumes due to statistics and seed isolation effects. PCM emulsions are superior in their heat transfer rates compared to larger PCM modules. In principle, the smaller the droplets, the larger is the risk for significant subcooling. Due to the limitations of theoretic models, it is necessary to use experimental investigations to predict from what droplet size on subcooling becomes problematic in a PCM. In this paper, we present an experimental study on subcooling in hexadecane emulsions. Different hexadecane–water–surfactant systems with droplet size in the range of about 0.1–20 μm were prepared and analyzed. We have observed an increased subcooling of at least 10 K for small droplets. The surfactants also have an impact on the melting and solidification temperatures.