Marijuana plants (and any other flowering plants) need 20 to 40 moles of light per day. That is equal to 20,000,000 to 40,000,000 umol (micro moles). The closer you can get to 40 moles, the better, in order to maximize yields.
If you are running your lights for 18 hours per day, those lights need to deliver a PPFD output of 617 umol, in order to add up to 40 moles per day. When you switch to 12 hours per day of lighting during flowering, that value jumps up to 926 umols, to make up for the 6 hours of lost lighting time per day. That is why you need more lighting power during flowering.
Even if you can’t provide that much light, as long as your plants are getting a total of 20 moles per day, they will grow and yield buds. But they will obviously not grow as fast or yield as much. To achieve a daily total of 20 moles, you need lights that deliver 308 umol during the 18 daylight hours of vegging and 462 umol during the 12 daylight hours of the bloom stage.
CSNJ LED Grow Light Apollo G630 is capable of PPF output up to 1700umol/s and the growers can achieve the PPFD up to 900umol/s/m2 in average on canopy of Marijuana when the light fixture is around 20” above the canopy. With the light if it’s switched on 12 hours every day, G630 can deliver 38.88 moles (900*3600*12/1000000) that is very closed to the target 40 moles per day.
Obviously, you can increase the daily total by running the lights for more hours, that is exactly why people run them 24 hours per day, or by adding more fixtures. But these solutions will increase the power consumption that increases the operation cost finally. Therefor to choose a higher efficiency light fixture will be important and CSNJ Apollo series are obviously a good choice.