Contributed by: Flowerman
It depends on what type of lamp you're using.
These recommendations are based on 18 hours of daily use.
Type When to replace
1000w (mh) lamps 12 months
1000w (mh) lamps "agro sun & warm deluxe 15 months
1000w (mh) lamps u cool deluxe 6500k 12 months
400w (mh) lamps 18 months
400w (mh) lamps u cool deluxe 6500k 15 months
250w (mh) lamps u cool deluxe 5400k 12 months
175w (mh) lamps daylight bulb 5500k 15 months
All regular 75w to 250w (mh) lamps 15 months
Replace all hps after 24 months, with the exception of the son agro and super agro, replace after 15 months. Fluorescents should be replaced every 15 months. After 12 months, check the tubes if running more than one tube on a single ballast. Always replace all fluorescent tubes at the same time. Remember to always write down the day that you start using a new HID lamp. This will allow you to calculate when to replace it for best results.