The objective of this paper is to investigate the performance of two different types of Solar Domestic Hot Water (SDHW) systems , one with a gasboiler as the auxiliary heating source and the other with an electric tank as the auxiliary heating source, and to investigate the contributions ofdifferent components of the systems in lowering the annual energy demand and GHG emissions for producing 225 litres (59.4 gal) per day ofdomestic hot water. The systems are for the twin Archetype Houses located in Vaughan, Ontario, Canada. The annual energy consumption of thegas boiler and electric tank from the experimental analysis were to be 3718.7 kWh (12.69 MBtu) and 2778 kWh (9.48 MBtu), respectively.The TRNSYS models of the two systems were also created and validated with the experimental results. Using the TRNSYS models for a typicalCanadian household in Toronto, Ontario, the annual energy consumption by the gas boiler and electric backup tank were concluded to be 3636.9kWh (12.41 MBtu) and 2681.5 kWh (9.15 MBtu), respectively. The annual thermal energy output by the flat plate and evacuated tube solarthermal collectors were found to 2010.8 kWh (6.86 MBtu) and 1390.6 kWh (4.74 MBtu), respectively. The annual heat recovery by theDrain Water Heat recovery (DWHR) units were concluded to be 792.8 kWh (2.7 MBtu).