A method for calculating power for a data storage system. The method includes: measuring power requirement for each one of a plurality of components for use in one of a plurality of possible system configurations; storing the measured power requirement in a table; entering into the table a specified one of the possible system configurations to obtain the power requirement for such one of the specified system configurations; calculating from the table the total power expected for the specified system configuration; presenting the calculated power to a user; determining whether the calculated power is acceptable or unacceptable to the user; and if determined to be unacceptable, entering into the table a new system configuration.