We study the nonequilibrium properties of an electronic circuit composed of a double quantum dot (DQD) channel capacitively coupled to a quantum point contact (QPC) within the framework of stochastic thermodynamics. We show that the transition rates describing the dynamics satisfy a nontrivial local detailed balance and that the statistics of energy and particle currents across both channels obeys a fluctuation theorem. We analyze two regimes where the device operates as a thermodynamic machine and study its output power and efficiency fluctuations. We show that the electrons tunneling through the QPC without interacting with the DQD have a strong effect on the device efficiency.The microscopic processes underlying such transitions involve the tunneling of an electron between the QPC reservoirs which exchanges a fraction of its energy with the DQD. As a result, the transition rates cannot be written anymore as a sum where each term only involves one single reservoir. Despite this non additivity of the rates, the local detailed balance (LDB) [37, 39] is shown to hold, and is explicitly written in terms of the fluxes of entropy from the reservoirs involved in the transitions.Furthermore, since some electrons tunnel between the QPC reservoirs without exchanging energy with the DQD, they do not induce transitions in the DQD but need to be taken into account in the counting statistics. We show that their statistics is well described by the modified quantum master equation and corresponds to the Levitov-Lesovik formula [40-44] to second order perturbation theory in the coupling between the QPC reservoirs. Though such processes do not reveal themselves in the master equation for the DQD populations, they are shown to strongly impact the circuit performance.We proceed by analyzing two different regimes where the circuit operates as a thermoelectric and as a current converter, respectively. We identify the optimal working conditions to reach large average output power and high macroscopic efficiency and study the statistical properties of the output power as well as of the efficiency, as recently proposed in [45][46][47].The paper is organized as follows: the model is introduced in section 2. In section 3, we derive the modified quantum master equation to calculate the counting statistics of energy and matter currents, and analyze the microscopic processes contributing to the transition rates. In section 4, using the LDB property of the rates, we identify the entropy flows associated to each microscopic processes in the circuit, and the steady state FT is derived. The expressions for the average energy and matter currents as well as the average irreversible entropy production are also provided. The thermodynamic analysis of the circuit operating as a thermoelectric and as a current converter is done in section 5. Conclusions are drawn in section 6. +--+ From these expressions, one readily verifies the conservation laws J J J J J J J 0, and . 69