The invention, intended primarily for use in a steel flywheel power source (30), provides a vacuum system and a method of maintaining a vacuum inside a flywheel chamber (32) for the life of the power source (30). The vacuum system combines the use of cleaning and de-gassing treatments in the chamber (32) and vacuum tempering of the steel flywheel (31) with the use of a chemical type metal alloy nonevaporable getter, such as zirconium-vanadium-iron, that cooperatively matches the outgassing of the flywheel (31) and chamber (32) by sorbing those gases that are released. The getter may be reactivated throughout the life of the flywheel system by reheating it with an integral heater that is triggered by a timer instead of a vacuum gauge to increase the system reliability, using power taken directly from the energy stored in the flywheel. The electronics (45) of the flywheel power source are used to signal an alarm or prevent achieving or maintaining full speed of the flywheel when the vacuum in the chamber degrades.