In modelling evapotranspiration, the need for land surface variables including ground heat fluxes (G), surface temperature (Ts), surface relative humidity (RHs) and surface resistance often present a challenge due to land heterogeneity and limited measurements. This study introduces a simple formulation rooted in the shared physical basis of the maximum entropy model (MaxEnt), the Relative Humidity at Equilibrium (ETRHEQ) method, and the Surface Flux Equilibrium (SFE) method, and it estimates sensible (H) and latent fluxes (LE) in wetlands without requiring land surface variables or site-specific calibration, except for an assumed vegetation height. Further, it effectively estimates LE from half-hourly to monthly scales in FLUXNET and AmeriFlux wetland sites. While its performance in estimating H is less satisfactory due to loosely constrained boundary conditions, it shows promising potential for simultaneously and precisely estimating LE, H, G, Ts, and RHs from weather data in various ecosystems.