grams/watts?

what is the rule of thumb for grams/watt?

Most people try and aim for 0.5g per watt.

When you have your environment dialed in and your nute schedule then you can try and aim for 1g per watt.

J

The best I've ever seen is about 0.95g per watt from a 600w HPS, experienced growers should be getting at least 0.5g per watt if they're getting less their not maximising their potential and if they're getting more they're doing something right.

There's a much more sophisticated system for calculating 'grow room efficiency' that does factor in the flowering time as well as lighting wattage -

Grow Room Efficiency Calculator

You need figures for -

Total light wattage
Total flowering time in days
Light cycle hours
Total yield in grams

For example. A 600w HPS system used on a 12/12 hourly cycle in flowering for 60 days which produces 20ozs (560g) of dry bud.

1) Divide total lamp wattage by 1000 to get Kw/h.
600w/1000 = 0.6.

2) Multiply this figure by the hours of the light cycle.
0.6 x 12 = 7.2

3) Multiply this figure by the number of days in flowering.
7.2 x 60 = 432

4) Now divide the gram yield figure by the kilowatt figure.
560g / 432 = 1.29. That's 1.29g per K/w

Experienced growers should be shooting for a GE (Garden Efficiency) rating of 1.0, so anything over 1.0 is very good going.

taken this from babygro https://www.rollitup.org/advanced-marijuana-cultivation/12620-post-how-many-do-you-2.html