Method for managing the energy of a hybrid power plant of a multi-rotor aircraft during a flight, said multi-rotor aircraft comprising: - a hybrid power plant provided with a thermal energy source, an electrical energy source and at least one electrical machine, said thermal energy source being capable of supplying continuous thermal power W Th, said at least one electrical machine being capable of supplying continuous electrical power W ElecCont and a maximum electrical power W ElecMax, and - at least two rotors rotated by said hybrid power plant, said flight comprising a take-off phase of a duration T TakeOff, a cruising phase of a duration T Cruise and a landing phase of a duration T Landing, said multi-rotor aircraft having a cruising power W Cruise necessary for carrying out a cruising phase, said take-off phase and said landing phase being carried out only by consuming electrical energy supplied by said electrical energy source, characterised in that said method comprises the following steps: - a first calculation of a take-off electrical energy E TakeOff consumed during the take-off phase and equal to: E TakeOff = W ElecMax. T TakeOff, - a second calculation of a landing electrical energy E Landing consumed during the landing phase and equal to: E Landing = W ElecMax. T Landing, - a third calculation of a cruising electrical energy E ElecCruise available for said cruising phase and equal to: E ElecCruise = E ElecTotal − W ElecMax. T TakeOff + T Landing, where E ElecTotal is the total electrical energy available in said electrical energy source before the start of said flight of said aircraft, - a fourth calculation of a cruising electrical power W ElecCruise available for said cruising phase and equal to: W ElecCruise = MIN W Cruise W ElecCont E ElecTotal − W EleMax. T TakeOff + T Landing T Cruise, - a comparison of said cruising electrical power W ElecCruise and said cruising power W Cruise, and - a determination of a cruising thermal power W ThCruise necessary for said cruising phase such that: ∘ if W ElecCruise = W Cruise; W ThCruise = 0, and ∘ if W ElecCruise < W Cruise; W ThCruise = W Cruise - W ElecCruise. - a hybrid power plant provided with a thermal energy source, an electrical energy source and at least one electrical machine, said thermal energy source being capable of supplying continuous thermal power W Th, said at least one electrical machine being capable of supplying continuous electrical power W ElecCont and a maximum electrical power W ElecMax, and - at least two rotors rotated by said hybrid power plant, - a first calculation of a take-off electrical energy E TakeOff consumed during the take-off phase and equal to: E TakeOff = W ElecMax. T TakeOff, - a second calculation of a landing electrical energy E Landing consumed during the landing phase and equal to: E Landing = W ElecMax. T Landing, - a third calculation of a cruising electrical energy E ElecCruise available for said cruising phase and equal to: E ElecCruise = E ElecTotal − W ElecMax. T TakeOff + T Landing, where E ElecTotal is the total electrical energy available in said electrical energy source before the start of said flight of said aircraft, - a fourth calculation of a cruising electrical power W ElecCruise available for said cruising phase and equal to: W ElecCruise = MIN W Cruise W ElecCont E ElecTotal − W EleMax. T TakeOff + T Landing T Cruise, - a comparison of said cruising electrical power W ElecCruise and said cruising power W Cruise, and - a determination of a cruising thermal power W ThCruise necessary for said cruising phase such that: ∘ if W ElecCruise = W Cruise; W ThCruise = 0, and ∘ if W ElecCruise < W Cruise; W ThCruise = W Cruise - W ElecCruise. ∘ if W ElecCruise = W Cruise; W ThCruise = 0, and ∘ if W ElecCruise < W Cruise; W ThCruise = W Cruise - W ElecCruise.