Method for regulation of a single-valve CO2 refrigerating apparatus which comprises, in sequence: - a compressor assembly; - a gas cooler connected to said compressor assembly so as to receive from it gas under pressure; - an expansion valve, with adjustable opening, located downstream of said gas cooler, for expanding the refrigerant fluid supplied from the latter; - an evaporator, located downstream of said valve and upstream of said compressor assembly; said apparatus further comprising: - temperature detection means (15a, 15b), configured to detect an overheating temperature value Tsh of said refrigerant fluid, by means of a temperature detection downstream of said evaporator or upstream of said compressor, and to detect a temperature value of the refrigerant fluid downstream of said gas cooler; - pressure detection means, for detecting a high-pressure value HP of the pressure of said refrigerant fluid downstream of said compressor assembly and upstream of said expansion valve; - a controller connected to said temperature detection means (15a, 15b) and to said pressure detection means, so as to receive data from them, and to said expansion valve so as to adjust said opening thereof according to said method; characterized in that said method comprises: - an operation A of detecting, over time, the value of a primary parameter and the value of a secondary parameter, wherein said primary parameter is chosen from said high pressure HP and said overheating temperature Tsh, where said secondary parameter is said overheating temperature Tsh if said primary parameter is said high pressure HP or is said high pressure HP if said primary parameter is said overheating temperature Tsh; - a primary regulation operation B, which involves regulation of said expansion valve so that the value of said primary parameter, detected in said operation A, tends towards a set-point value; - an operation C of estimating an optimal value Vo for said secondary parameter, where said optimal setpoint value V 0 is estimated according to an algorithm for energy optimization of said refrigerating apparatus; - a secondary regulation operation D which involves varying said set-point value from an optimal set-point value or from a current value if the value of said secondary parameter, detected in said operation A, does not fall within a predefined tolerance range It of values comprising said optimal value Vo; where said variation is made so as to tend to bring the value of said secondary parameter back within said tolerance range It. - a compressor assembly; - a gas cooler connected to said compressor assembly so as to receive from it gas under pressure; - an expansion valve, with adjustable opening, located downstream of said gas cooler, for expanding the refrigerant fluid supplied from the latter; - an evaporator, located downstream of said valve and upstream of said compressor assembly; - temperature detection means (15a, 15b), configured to detect an overheating temperature value Tsh of said refrigerant fluid, by means of a temperature detection downstream of said evaporator or upstream of said compressor, and to detect a temperature value of the refrigerant fluid downstream of said gas cooler; - pressure detection means, for detecting a high-pressure value HP of the pressure of said refrigerant fluid downstream of said compressor assembly and upstream of said expansion valve; - a controller connected to said temperature detection means (15a, 15b) and to said pressure detection means, so as to receive data from them, and to said expansion valve so as to adjust said opening thereof according to said method; - an operation A of detecting, over time, the value of a primary parameter and the value of a secondary parameter, wherein said primary parameter is chosen from said high pressure HP and said overheating temperature Tsh, where said secondary parameter is said overheating temperature Tsh if said primary parameter is said high pressure HP or is said high pressure HP if said primary parameter is said overheating temperature Tsh; - a primary regulation operation B, which involves regulation of said expansion valve so that the value of said primary parameter, detected in said operation A, tends towards a set-point value; - an operation C of estimating an optimal value Vo for said secondary parameter, where said optimal setpoint value V 0 is estimated according to an algorithm for energy optimization of said refrigerating apparatus; - a secondary regulation operation D which involves varying said set-point value from an optimal set-point value or from a current value if the value of said secondary parameter, detected in said operation A, does not fall within a predefined tolerance range It of values comprising said optimal value Vo; where said variation is made so as to tend to bring the value of said secondary parameter back within said tolerance range It.