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The performance of photovoltaic (PV) modules and systems is affected by the orientation and tilt angle, as these parameters determine the amount of solar radiation received by the surface of a PV module in a specific region. In this study, three sky models (Liu and Jordan, Klucher, and Perez et al .) are used to estimate the tilted irradiance, which would be received by a PV module at different orientations and tilt angles from the measured global horizontal irradiance (GHI) and diffuse horizontal irradiance (DHI) in Singapore (1.37°N, 103.75°E). Modeled results are compared with measured values from irradiance sensors facing 60° NE, tilted at 10°, 20°, 30°, 40°, and vertically tilted irradiance sensors facing north, south, east, and west in Singapore. Using the Perez model, it is found that a module facing east gives the maximum annual tilted irradiation for Singapore's climatic conditions. These findings are further validated by one-year comprehensive monitoring of four PV systems (tilted at 10° facing north, south, east, and west) deployed in Singapore. The PV system tilted 10° facing east demonstrated the highest specific yield, with the performance ratio close to those of other orientations.