Does CO2 heat pump require big Delta T?

it depends on the projects and usage of the heat pump. For under floor heating or low temperature radiator, the normal setting is 25°C/35°C.Under this small delta T condition, CO2 heat pump can also work with very high COP, its efficiency is similar with the conventional heat pump like R32 or R290. For domestic hot water, the normal  setting is 15°C/55°C, under this big delta T condition, CO2 heat pump performs the best among different refrigerants.