There are many well known researches and commercial products for solar air-conditioning (SAC) units of small and medium power (up to 100 kW). Solar energy application for refrigeration by using of the sorption cycle for Latvian climate conditions was considered in the presented paper. Advantages of lithiumbromide and ammonia-water fluids were compared taking in account the difference between real and ideal performance of the sorption systems. Since heat rejection in thermally driven chillers is bigger than in conventional vapor compression refrigeration, the climate conditions have big influence on the total system performance. As the solar radiation level in Latvia is less than 400 W·m-2 dual sources of driving heat (biofuel combustion and solar energy) for the sorption cycle were evaluated. Computer modeling of sorption chillers results in development of a new temperature threshold criterion for efficient use of solar cooling systems at different energy costs and various temperature levels.