Which substance is commonly used as a refrigerant in residential A/C systems?

R-410A is commonly used as a refrigerant in residential air conditioning systems due to its efficiency and environmentally friendly properties. This refrigerant is a hydrofluorocarbon (HFC) that does not deplete the ozone layer, making it a more suitable alternative to older substances like R-22, which is being phased out due to its ozone-depleting potential.

R-410A has a higher cooling capacity and operates at higher pressures, which allows for improved performance in residential systems. It also contributes to higher energy efficiency ratings for air conditioning units, leading to lower energy costs for consumers. This makes R-410A the preferred choice in modern residential air conditioning installations.