The performance of a DHW system fitted with flat-plate and vacuum collectors has been analysed. Simulations were carried out on the basis of equal aperture or gross areas of basis using TMY data for hour-by-hour dynamic simulation generated for 1036 sites located in different regions of the world. The performance indicators of solar fractions and number of days were determined for specific water mean temperatures in the storage tank of 37 °C, 45 °C and 55 °C. It has been shown that vacuum tube collectors provide slightly better DHW performance indicators than typical flat-plate collectors having the same aperture area. However, since the space that needs to be provided and directly or indirectly paid for is what matters to the user of solar heating systems, the analysis was also carried out on equal gross area basis; on this basis, the advantages of using vacuum collectors are not obvious.