A generator comprising: - a vertical supply column that can be filled with a certain quantity of liquid; - an intake valve disposed at a base of the vertical supply column; - a leaktight tank communicating with the vertical supply column via said intake valve, which leaktight tank is capable of being filled with liquid; - an exhaust valve disposed on said leaktight tank and capable of releasing pressure generated in said leaktight tank; - a piston-forming device disposed inside said leaktight tank so as to be immersed in the liquid contained in the leaktight tank, which piston-forming device is capable of being set in reciprocating movement between an upper position and a lower position, the piston-forming device comprising a first, float-forming portion capable of bringing the piston-forming device into the upper position and a second portion forming an output shaft; and - a converter device coupled to the output shaft, which converter device is capable of converting the reciprocating movement of the piston-forming device into mechanical or electrical energy, said generator being configured in such a way that, in operation, the leaktight tank is filled with liquid, and in such a way as to repeat the following sequence of operating phases in order to induce the reciprocating movement of the piston-forming device, namely: - a first operating phase during which the intake valve is closed and the vertical supply column is filled with liquid so as to form a column of liquid above the leaktight tank; - a second operating phase during which the exhaust valve is closed and the intake valve is open in order to connect the vertical supply column and the leaktight tank, generating an increase in pressure in the leaktight tank and causing a displacement of the piston-forming device to the lower position; and - a third operating phase during which the intake valve is closed and the exhaust valve is open in order to release excess pressure formed inside the leaktight tank, allowing the piston-forming device to return to the upper position under the action of the first, float-forming portion. - a vertical supply column that can be filled with a certain quantity of liquid; - an intake valve disposed at a base of the vertical supply column; - a leaktight tank communicating with the vertical supply column via said intake valve, which leaktight tank is capable of being filled with liquid; - an exhaust valve disposed on said leaktight tank and capable of releasing pressure generated in said leaktight tank; - a piston-forming device disposed inside said leaktight tank so as to be immersed in the liquid contained in the leaktight tank, which piston-forming device is capable of being set in reciprocating movement between an upper position and a lower position, the piston-forming device comprising a first, float-forming portion capable of bringing the piston-forming device into the upper position and a second portion forming an output shaft; and - a converter device coupled to the output shaft, which converter device is capable of converting the reciprocating movement of the piston-forming device into mechanical or electrical energy, - a first operating phase during which the intake valve is closed and the vertical supply column is filled with liquid so as to form a column of liquid above the leaktight tank; - a second operating phase during which the exhaust valve is closed and the intake valve is open in order to connect the vertical supply column and the leaktight tank, generating an increase in pressure in the leaktight tank and causing a displacement of the piston-forming device to the lower position; and - a third operating phase during which the intake valve is closed and the exhaust valve is open in order to release excess pressure formed inside the leaktight tank, allowing the piston-forming device to return to the upper position under the action of the first, float-forming portion.