what exactly is productivity?

[Paulio]

hi folks, as the title says, i'd like to know what productivity is. because i don't know what exactly the productivity modules do, but they must be nice if you look at the high costs of power consumption.

[wrtlprnft]

Productivity increases the output of your assembler/furnace. If you have a productivity bonus of 0.2, for each five items that are assembled/smelted, another one will be generated, without using additional ingredients. To show your progress towards the extra “free” item, the GUI has an additional purple bar below the usual green one.

[Paulio]

thanks

[Holy-Fire]

but they must be nice if you look at the high costs of power consumption.

They are. Used properly, they are much more powerful than any of the other modules.

[n9103]

The higher the raw costs in items produced, the bigger the overall gain from productivity bonuses.
However, using them on end-item assemblers can be counter productive if that item isn't in constant production.
Optimal placement is a matter of the highest res cost item that's being constantly produced.

The above assume that space isn't an issue, and that your factory can expand in any needed area.
If those aren't true, then you're probably going to focus on putting them in the non-expandable areas.

Some people would recommend putting them into the electric furnace, but I wouldn't unless you're at the point that all more expensive items have already been boosted.
The increase in raw material available, and slight boost to how quickly it's available, is FAR outdone by even a 'Basic Circuit' assembler, unless you're in the situation where it's not possible to fully supply your smelting needs with ore. (super dense creepers around the only patches, limited map distances, etc)

[Holy-Fire]

The higher the raw costs in items produced, the bigger the overall gain from productivity bonuses.
However, using them on end-item assemblers can be counter productive if that item isn't in constant production.
Optimal placement is a matter of the highest res cost item that's being constantly produced.

The above assume that space isn't an issue, and that your factory can expand in any needed area.
If those aren't true, then you're probably going to focus on putting them in the non-expandable areas.

Some people would recommend putting them into the electric furnace, but I wouldn't unless you're at the point that all more expensive items have already been boosted.
The increase in raw material available, and slight boost to how quickly it's available, is FAR outdone by even a 'Basic Circuit' assembler, unless you're in the situation where it's not possible to fully supply your smelting needs with ore. (super dense creepers around the only patches, limited map distances, etc)

Good analysis. I'd like to add that:

1. It's not just the raw cost that matters, it's raw cost divided by assembly time. So blue potion is good, not great, because of the slow production; smart inserters are usually better if you have to choose, and advanced electronics circuit are a killer if it's fully utilized. This, by the way, is another reason why electric furnaces should be last in line; their cycles are longer.

2. You need to consider not the displayed raw cost, but the cost corrected for modules you already use. For example, if you're at +100% productivity for smart inserter, then each smart inserter is actually about half the listed cost. You need to consider this when calculating the resource cost of blue potion. Advanced users can also consider the embodied energy in the ingredients. For machines that are not fully utilized, the base lucrativeness should be multiplied by the % utilization. In the endgame when everything is plentiful, anything with alien artifacts should take priority.

3. Even in the worst places for productivity modules, they are still better than other modules. For example, copper cable (1 copper plate per second). Assembling machine 2 completes about 1 cycle in a second, consuming 150 J. Efficiency cuts 50% and productivity adds 50%, so using productivity wastes 150J per cycle, which is 0.0375 units of coal; and the productivity module gains you an extra 0.05 units of copper (with the nice side effect of making the machine faster). This is even better with higher-level modules; level 3 adds thrice as much productivity, but elec costs is less than twice as much. If you're using solar, it means you think it is cheaper than coal, making the gap even greater.

4. My preferred layout has each beacon affecting 8 machines, and each machine affected by 2 or 4 beacons. So you can have productivity of +90% or +120%. You should place the more lucrative machines in the 4-beacon slots. And if you have a favorite machine (Alien science packs maybe?), surround it with 12 beacons for +240% productivity fun!