CO2 in small grow closet

Hello everyone,
I was thinking about adding a CO2 emitter to my small grow closet. I only grow 2 to 3 plants at a time, and was wondering if it would be worth it. My grow area is 4 x 4 x 7 feet. The cost of the emitter and timer is about 150 dollars, plus tank rental. I would appreciate any opinions on this, weather or not it would increase my yield enough to matter.
Thanks for you help.

If you are at maximum returns now, then adding CO2 will get you up to 20-30% more yield. If you are not already maxxed out on genetic growth, then your looking at less yield, more like 10% added.

Thanks NoDrama, I guess I don't know what you mean by max returns. I've been growing indica dominant strains, and putting them into flower after 3 weeks. I've been yielding between 3 and 4 ounces per plant dried. They veg under CFL's, and Flower under a 400 watt HPS. If there is anything wrong with what I'm doing please comment on that as well. Thanks again.

Hi,

I have a slightly smaller cabinet and have tried CO2 but couldnt do it.
My problem is I need to exhaust so frequently I could only keep CO2 in there when the lights were off.

You may want to time your exhaust cycles before you invest.

Good Luck