Not sure which type of T8 fluorescent ballast you need? Instant start and programmed start ballasts are both great technologies, but they are intended for different applications.
Quickest, most energy-efficient, instant-on lighting intended for areas with infrequent switching and "on" cycles of several hours. Ideal for offices, warehouses, and retail spaces.
Slower starting, energy-efficient lighting that prolongs the life of lamps and performs well in frequently switched applications or in areas controlled by an occupancy sensor. Ideal for hallways, stairwells, and bathrooms.