I'm asking because although I've read posts I haven't understood all I've seen. My question is what are the generally accepted measures of a good yield. eg
2 oz per plant? 1 gram per watt of light? 1 gram per kwh expended? So what are some accepted parameters and what yields are considered poor, fair, excellent? OK, that was multiple questions. Thanks.
Its complicated.
Yield per plant isn't very helpful, because plants can range is size from 12 inch high single-cola plants that yield half an ounce to 4 foot high several foot wide monster SCROGs with 64+ tops that yield nearly a pound each.
As a very first bare rule of thumb, if you're running an efficient commercial-style setup, yes, your target might be 1 gram yield per watt, but note that strain matters here, as, of course does setup.
Some strains will give you higher yields of lower-potency bud. Is that really what you want?
Some strains may give you high yields, but will take long flowering times to get there. Again, is that really what you're after?
I'd say the best way to measure/express the efficiency of a grow system is yield per watt
per unit time (yes, you could use yield/kWh), though in practice, most people don't do it that way. You also have to take into account energy used in cooling, ventilation, and running hydro systems, and again, lots of people don't.
In general, I'd say these sorts of measures are more important to professional cash-croppers and for bragging rights.
If you're just growing for personal use, does it really matter if you get 0.8 grams per watt, or 0.6 grams per watt? Of course if you can maximize yields with any given setup that's great, but ultimately, as long as you are generating enough buds to maintain your supply and you're not tremendously wasteful of energy, then you're doing fine.
Also, I'd add that in GENERAL, the bigger the setup, the more efficient its possible to be. Its a lot easier to yield 1 g/w under a 600w HPS in a big room than it is under 2 23W CFL lamps in a small box. High efficiency setups also typically grow large numbers of the SAME type of plant (maximizing nute, harvest, and other efficiencies), use hydroponics (which tend to increase yields over soil) and use sea-of-green or extensive trellising systems to improve yield. Pro growers will also run the same strain again and again, so they are totally familiar with it and know how to max yields.
While all of these things can be done on a smaller scale, that doesn't mean they "need" to be. For example, there is something to be said about trying to grow different strains in sequence, just to gain experience in growing and smoking them, rather than trying to max efficiency with the same strain.
Simon