This paper describes a hybrid photovoltaic-thermal systems with water and air as a coolant, with detailed description of the components of which PV/T system consists . Simulation model of PV/T system with direct or indirect fluid flow is developed in Matlab/Simulink. The model is based on energy balances of photovoltaic module, solar collector and heat storage tank. Conditional activation of the pump is taken into account, which is dependent on the temperature of water in the collector and storage tank, and maintaining the desired temperature of domestic hot water in storage tank or photovoltaic module. The influence of system performance (direct and indirect flow), the thermal stratification in the system, radiation and the operating temperature of the photovoltaic cells on the dynamics of temperature changes in the thermal tank, and electrical and thermal efficiency of the system are observed. The system for measuring the temperature of hybrid photovoltaic-thermal system was elaborated at the Faculty of Electrical Engineering and Computing in Zagreb, and was successfully mounted on PV / T system also handmade in FER. The system is using a Bluetooth^TM technology and 1-wire temperature sensors. The system is controlled by using a LabVIEW application. Nine-point temperature on the back of the PV module, the water temperature at the outlet of the collector and the temperature in the water tank were measured. It was observed how the temperature of the module affects the electrical and thermal efficiency of the system, and the maximum power output. Temperature measurements at the outlet of the collector and the tank were used to calculate the thermal efficiency of the system. Output voltage and load current connected to the photovoltaic module were used in calculating the electrical efficiency of the system.