The article considers the hovering ceiling of an unmanned electric multi-rotor helicopter (multicopter) — the height where all available power is equal to the power required to hovering with a given flight weight. In determining the static ceiling of the electric multicopter, the aircraft features distinguishing them from conventional helicopters, are taken into account. It is found that the hovering ceiling of an electric multicopter is determined by the thrust-to-weight ratio and rigidity of the electric motor mechanical characteristics. The analysis of a typical quadrocopter configuration shows that the value of the hovering ceiling can be at least 5000 m. The dependence of the hovering ceiling on the supply voltage is studied; the decrease of the voltage significantly affects the hovering ceiling. The dependence for the minimum value of the thrust reserve ensuring the flight of the multikopter at a given decrease in the supply voltage during the flight is deduced from the formulae for the hovering ceiling. The formula and tables for calculating the minimum thrust-to-weight ratio, allowing estimation of these values when designing a multikopter, are given