A pumping system pumps material or fluid, for example, downhole to perform a stimulation operation. A pumping system may comprise multiple pumps that must be powered-up in a sequence that does not overload a power source. A variable frequency drive may be coupled to a pump via a motor and may adjust the speed of the motor to control the rate of pumping of fluid from the pump. A soft-starter may be coupled to a pump via a motor to provide a constant pumping rate of fluid from the pump. A power-up sequence may be determined that provides power to the variable frequency pump and the soft-starter to power-up the corresponding motors such that the power source is not strained or overloaded. Mixing variable frequency drive driven pumps with pumps driven by a soft-starter may provide an efficient use of available power, conserve space, allow for control over a pumping rate of fluid and reduce costs.