Hello Professor Lee,
What are the advantages to buying a ballast with an adjustable wattage control? If I buy one 1000-watt light why wouldn’t I want it to run at full strength?
This feature is commonly used to tailor the intensity of light for plants during different stages of plant growth. For example, if you had a bunch of young sprouts/seedlings and used your 1000-watt light at full power you would have to raise it far above the plants to prevent heat stress. Plus using that much power on sprouts and seedlings wastes a lot of electricity. Having an adjustable ballast lets you keep the lights much closer to the plants and saves a huge amount on your electric bill. After the plants pass the delicate seedling stage and become mature veg plants, the wattage can be increased and so on until harvest.
I hope this helps!