As other people say, you are only looking at part of the picture. Plants need different wavelengths and these change through the plant's lifecycle. LEDs are no

As other people say, you are only looking at part of the picture. Plants need different wavelengths and these change through the plant's lifecycle. LEDs are not optimal but plenty of people have reasonable success with them. Personally I have a 250w metal halide. My electricity is $0.12 per kW/h so 10 hours per day costs me $0.40. I grew with fluorescent before that and I would use that again. I don't grow cannabis - chillis and basil at the moment but come spring I use it to sprout seedlings for the University allotment.