This paper investigates the use of two low global warming potential working fluids, HCFO-1224yd(Z) and HCFO-1233zd(E), in high-temperature heat pump systems. A simulation was performed at evaporating temperatures ranging from 50–70°C and a condensing temperature of 110°C. A solar thermal collector was used to supply the energy needs on the evaporator side. Energy, exergy, and environmental analyses were performed to evaluate both environmentally friendly refrigerants and compare them to HFC-245fa. The coefficient of performance (COP) and total exergy destruction represented the performance of the system, while the total equivalent warming impact was used to evaluate the environmental effect of each refrigerant. At an evaporation temperature of 50°C, HCFO-1224yd(Z) and HCFO-1233zd(E) showed comparable performance to R245fa, with COP values of about 2.74 and 2.69, respectively (R245fa had a COP value of about 2.66). The same results were also obtained at evaporation temperatures of 60°C and 70°C, at which R1224yd showed good performance compared to R1233zd and R245fa with COP values of 3.6 for 50oC evaporation temperature and 4.75 for 70oC evaporation temperature. Additionally, both suggested refrigerants had low direct emission compared to R245fa based on the results from the environmental analysis.