To replace 2;1000w hps lights you need roughly 1000-1200w of leds.
Here on this thread I did some rough math on page 7
https://www.rollitup.org/t/are-cobs-worth-it.910069/
Now let me come from a different perspective other than gpw. What about the heat and also the amount of electricity used?
To properly light up a 4x8 tray you need 2; 1,000 watt lights or 1,000-1200 watts of leds. We'll go with 1,000 watts of led to make the math work out a lil better.
Hps = 1000w being 35% efficient
Heat = 650w of heat energy
750w x 2 = 1300w of heat energy.
Led = 1000w being 56% efficient
Heat = 440w of heat energy
Air cooled lights generally remove half the heat that is produced, unless of course you have multiple 1000's on the same inline fan.
So.. final numbers.
Air cooled Hps = 1300w / 2 = 750w of heat energy
Led = 440w of heat energy
So you can see we save on 32% on heat moving to led.
Now talking about
photon output...
Hps
1; 1,000w Hps = 35% efficent which is 350 watts for photons
2; 1,000w Hps = 350w x 2 = 700w for photons
Led
1; 1,000w of led's = 560w for photon output.
The small difference of 140w is EASILY disregarded as the glass takes at least 10% of the light output.
Hps = 700w x .10(glass absorption) = 70w
Final Numbers for photon output
Hps
2; 1,000w Hps = 700w - 70w = 630w for photon output
Led
1; 1,000w of led's = 560w for photon output.
The hps focuses the light straight down so your wasting light in the middle. The plant doesnt need such strong light. At a point the plant cant do anything with the strong light due to limiting factors like co2 or even feed/genetics etc. Long story short your wasting a dick ton of light in the middle.
Led will allow you to achieve basically the same photon output with a EVEN SPREAD while saving 32% heat WHILE cutting your bill in half. If you grow.. then you know you'll pull some weight. The even spread is why I find led's worth it. Your not wasting any light and the quality is dam good.
Most average growers get about a pound a light which is about .5 GPW, if you keep the same amount of light and spread it out evenly? Fuck outta here thats how led growers get 1 GPW to 2 GPW.
Nearly costs $2,000 for a 1,000w led set up but if your in the money? Get it, it'll pay for itself in your cooling costs, hps bulb replacement cost, and electricity used. Its worth it if you can shell out the big bucks.
Now to continue and answer your question I believe that 1050ma-1400ma is the best current to drive them at. If you use 1050 you need 5 cobs per 200w. If you run them at 1400ma you only need 4 so per bar you save roughly 50 bucks. If you run at 1400ma then you need 20 cobs for 1000w, 24 cobs for 1200w of led's.
Yield is debatable as its case by case with the growers. If you get .5gpw which isnt bad at all then you can expect 1gpw with cobs. But if you pull upwards of .7gpw you can easily pull 1.5-2gpw with cobs.