Coastal and inland dunes provide various ecosystem services that are related to groundwater, such as drinking water production and biodiversity. To manage groundwater in a sustainable manner, knowledge of actual evapotranspiration ( ET a ) for the various land covers in dunes is essential. Aiming at improving the parameterization of dune vegetation in hydro-meteorological models, this study explores the magnitude of energy and water fluxes in an inland dune ecosystem in the Netherlands. Hydro-meteorological measurements were used to parameterize the Penman–Monteith evapotranspiration model for four different surfaces: bare sand, moss, grass and heather. We found that the net longwave radiation ( R nl ) was the largest energy flux for most surfaces during daytime. However, modelling this flux by a calibrated FAO-56 R nl model for each surface and for hourly time steps was unsuccessful. Our R nl model, with a novel sub-model using solar elevation angle and air temperature to describe the diurnal pattern in radiative surface temperature, improved R nl simulations considerably. Model simulations of evaporation from moss surfaces showed that the modulating effect of mosses on the water balance is species dependent. We demonstrate that dense moss carpets ( Campylopus introflexus ) evaporate more (5%, +14 mm) than bare sand (total of 258 mm in 2013), while more open structured mosses ( Hypnum cupressiforme ) evaporate less (−30%, −76 mm) than bare sand. Additionally, we found that a drought event in the summer of 2013 showed a pronounced delayed signal on lysimeter measurements of ET a for the grass and heather surfaces respectively. Due to the desiccation of leaves after the drought event, and their feedback on the parameters of the Penman–Monteith equation, the potential evapotranspiration in the year 2013 dropped with 9% (−37mm) and 10% (−61 mm) for the grass and heather surfaces respectively, which subsequently led to lowered ET a of 8% (−29 mm) and 7% (−29 mm). These feedbacks are of importance to water resources, especially during a changing climate with increasing number of drought days. Therefore, such feedbacks need to be integrated into a coupled plant physiological and hydro-meteorological model to accurately simulate ET a . In addition, our study showed that groundwater recharge in dunes can be increased considerably by promoting moss vegetation, especially of open structured moss species.