Method of configuring a rotary wing aircraft, the rotary wing aircraft incorporating an electrical installation and pieces of equipment consuming electrical energy, the electrical installation comprising at least one thermal battery and being suitable for delivering on demand, a predetermined quantity of electrical energy to at least one piece of consuming equipment, the method comprising at least a step of supplying the electrical installation and pieces of consuming equipment (5, 9, 11, 12, 13, 14) according to a definition of technical specifications of said at least one battery and the electrical installation in operational terms, in structural terms and in terms of arrangement within the aircraft, the step of supplying according to the technical specifications comprising: - a usable power to be provided by said at least one thermal battery as a function of the quantity of electrical energy to be delivered by the electrical installation for at least said consuming equipment, - a power rise time lapse of said at least one thermal battery, for rising at least to the predetermined quantity of electrical energy, - a low operating time for useful provision of the predetermined quantity of electrical energy to at least said consuming equipment, by said at least one thermal battery, - an availability time t availability during which said consuming equipment does not require energy but said at least one thermal battery remains hot for use at any moment, characterised in that the usable power is predetermined between 20 watts and 200 kilowatts, the power rise time lapse is comprised between 3 seconds and 30 seconds, the low operating time for useful provision is comprised between 10 seconds and 180 seconds, and the availability time t availability is comprised between 10 and 300 seconds; and in that the step of supplying according to the definition of technical specifications comprising at least one maximization routine for maximizing the quantity of usable power provided P load (t) as a function of time "t" upon the activation of said at least one thermal battery, the maximization routine controlling an impedance-matching electrical operation of said at least one piece of consuming equipment or load, the maximization routine assuming that said at least one thermal battery is equivalent, according to a Thévenin conversion model, to a looped linear electric circuit, to which applies in series the resistance R battery of the battery and the resistance R load of the equipment, an electromotive force EMF battery of the battery, an intensity I battery (t) of the electric current and a load electric voltage U load (t) of the equipment, such that the maximization routine determines a load voltage value U load (t) which cancels the derivative: dP load t dl load t = EMF battery − 2 ∗ R battery t ∗ l load t = 0 the load voltage U load (t) being reached when the resistance R load of the equipment is equal to the resistance R battery of the battery forming the source, such that the maximization routine adapts said load voltage U load (t) so as to obtain: U load t = EMF battery 2. - a usable power to be provided by said at least one thermal battery as a function of the quantity of electrical energy to be delivered by the electrical installation for at least said consuming equipment, - a power rise time lapse of said at least one thermal battery, for rising at least to the predetermined quantity of electrical energy, - a low operating time for useful provision of the predetermined quantity of electrical energy to at least said consuming equipment, by said at least one thermal battery, - an availability time t availability during which said consuming equipment does not require energy but said at least one thermal battery remains hot for use at any moment,