Thermodynamic modeling of a residential heat pump for combined space and water heating using binary CO2-based mixtures

•An in-house model was used to analyze CO2-based mixtures performance on a heat pump.•The analysis covers gas coolers number and position used to space and water heating.•Heat pumps mainly dedicated to water heating perform better with mixtures rich in CO2.•Refrigerant mixtures with low fraction of CO2 suits demands focused on space heating.•Most studied refrigerants increase the heat pump COP from mixtures with CO2.