I’m always looking for an easy way to start seedlings, flower a male, or stick a few plants into random closets and nooks in the house. I love the way simple LED bulbs at the hardware store have been getting more efficient over the years.
Here’s my latest favorite bulb - 5000K Philips 20-watters that produce 2175 lumens. A friend of mine uses these in springtime to veg his monster outdoor plants in 5-gallon containers with great success. The plants stay short with thick stems. He maxes out the containers under the bulbs and then transplants outdoors and gets 12-foot high sativa bushes.
also I found this cool website that lets you convert lumens to PAR - according to this, each bulb produces ~38 PPF which would be around 1.9 umol/j which would be the most efficient bulb I’ve found so far: