We investigate electron heating by magnetic-field-aligned electric fields (EII) during antiparallel magnetic reconnection in the Earth's magnetotail. Using a statistical sample of 140 reconnection outflows, we infer the acceleration potential associated with EII from the shape of the electron velocity distribution functions. We show that heating by EII in the reconnection outflow can reach up to 10 times the inflow electron temperature. We demonstrate that the magnitude of the acceleration potential scales with the inflow Alfve<acute accent>n and electron thermal speeds to maintain quasineutrality in the reconnection region. Our results suggest that, as the inflow plasma parameter /3e infinity increases, EII becomes increasingly important to the ion-to-electron energy partition associated with magnetic reconnection.