We construct the canonical ensemble of a $d$-dimensional Reissner-Nordström black hole spacetime in a cavity surrounded by a heat reservoir through the Euclidean path integral formalism. The cavity radius $R$ is fixed, and the heat reservoir is at a fixed temperature $T$ and fixed electric charge $Q$. We use York’s approach to find the reduced action by imposing the Hamiltonian and Gauss constraints and the appropriate conditions to the Euclideanized Einstein-Maxwell action with boundary terms, and then perform a zero loop approximation so that the paths that minimize the action contribute to the partition function. We find that, for an electric charge smaller or equal than a critical saddle electric charge $Q_s$, there are three solutions $r_{+1}$, $r_{+2}$, and $r_{+3}$, such that $r_{+1}<r_{+2}<r_{+3}$. The solutions $r_{+1}$ and $r_{+3}$ are stable within the ensemble, while $r_{+2}$ is unstable. For an electric charge equal to $Q_s$, the solution $r_{+2}$ merges with $r_{+1}$ and $r_{+3}$ at a given specific temperature. For an electric charge larger than $Q_s$, there is only one solution $r_{+4}$, which can be seen as the merging of the $r_{+1}$ and $r_{+3}$ solutions, with $r_{+4}$ being stable. Since the partition function is directly related to the free energy in the canonical ensemble, we read off the free energy and calculate the thermodynamic variables, namely the entropy, the thermodynamic electric potential, the thermodynamic pressure, and the mean energy. We investigate thermodynamic stability, which is controlled by the positivity of the heat capacity at constant area and electric charge, and show that the heat capacity is discontinuous at the electric charge $Q_s$, signaling a turning point. We analyze the favorable states, examining the free energies of the stable black hole solutions and the free energy of electrically charged hot flat space, in order to check for possible first and second order phase transitions between the possible states. For instance, the two stable black hole solutions $r_{+1}$ and $r_{+3}$ are in competition between themselves, more specifically, for certain ensemble parameters there exists a first order phase transition from one solution to the other, and at the critical charge $Q_s$ this transition turns into a second order phase transition. We also compare the thermodynamic radius of zero free energy with the generalized Buchdahl bound radius, which do not match, and comment on the physical implications, such as the possibility of total gravitational collapse of the thermodynamic system. We study the limit of infinite cavity radius and find two possibilities, the Davies and the Rindler solutions. The Davies thermodynamic solution of electrically charged black holes in $d=4$ dimensions is recovered from the general $d$-dimensional canonical ensemble analysis. We obtain, in particular, the heat capacity given by Davies and the Davies point. The Rindler solution describes the black hole horizon as a Rindler horizon, and the boundary, which is at fixed temperature $T$ provided by the reservoir, must have the necessary acceleration to reproduce the corresponding Unruh temperature. Going back to a cavity with finite radius we find that the three solutions mentioned above are related to the original York two Schwarzschild black hole solutions and to the two Davies solutions, with the middle unstable solution $r_{+2}$ belonging simultaneously to the two sets of solutions. In this sense, York’s and Davies’ formalisms have been unified in our approach. In all instances we mention carefully the four-dimensional case, $d=4$, for which we accomplish new results, and study in detail all aspects of the five dimensional case, $d=5$.