I switched to cob from hps, mh, cmh, blurple led and T5.
See I don't know much about commercial grows, but I do know lots about filling tents with buds, in small apartments, in multiple rooms.
So I have 2 spare rooms. Both are quite small. So in the winter I could grow with a 1000w hps in each, but that is it, the whole place would be so hot I would have two 4ft x 4ft tents and nothing more.
For me these comparison grows make it difficult for themselves. If I did a comparison grow, I would do one 4ft x 4ft tent with 1000w hps vs two 4ft x 4ft tents with 500w of cob in each. That also raises another point. Could I not cut the time half with 2 tents using the same amount of electricity? Do people take that into consideration.
My set up was 3500w + fans. Costing me £900 every 3 months.
My set up is now:
4ft x 4ft tent 450w cobs
4ft x 4ft tent 450w cobs
3ft x 3ft tent 300w cobs
3ft x 3ft tent 300w cobs
1.5ft x 2.5ft 100w cobs
2.5ft x 2.5ft 90 blurple led.
I will add that I've been vegging on half power too. My panels are pre made so I can have the 450w panels at 200w, 250w or 450w. My 300w panels are running on half power at 150w.
Vegging 6 set up's, on 990w, plus a few clip on fans and 5'' extraction. The windows are almost closed to keep the ambient temps up high enough. I'm saving a fuck load of money in electricity! I'm using just less than 1/4 of what I was using. In flowering on full power I'll be using just 1690w, including the veg tents usage too.
My 250w hps (275w draw) never vegged as well as my 250w of cobs.
Efficiency ain't eve the main reason why I switched either. I have complex ptsd from when I abused as a child. Jesus fucking Christ... is it just me, or do the loud extraction fans not severely fuck with your heads? That's the reason I changed, because it was sending me crazy sleeping in what sounded like a factory. WEEEEEEEEEEEERRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR all night long 24/7. Drove me nuts man!
It's not far off silent now!
Don't always assume efficiency is the best reason the change to cobs. For me, quiet extraction with double the grow area is far more appealing than figures.