Greenhouse growers may not need to invest in hi-tech grow lights.
If sunlight is sufficient for quality growth during the day, you may only need to provide interruption lighting at night.
To avoid flowering, growers implement brief bursts of light at night to keep the plants in a vegetative state of growth until they are ready to flower.
This can be accomplished with simple lights that run for two 15-minute intervals during the night. They can be LEDs or compact fluorescents. I have even seen growers use basic incandescent bulbs for this purpose.
Unlike primary or supplementary crop lighting, interruption lighting doesn't need to be strong enough to support healthy plant growth, only bright enough to interrupt flowering.
If you're lucky enough to cultivate where the sun provides sufficient light, skip the expensive grow lights and get creative with some alternative options. Your plants won't know the difference!