Line loss - Frequently asked questions

Q: What does this mod do?
A: It is an add-on for Power Overload. Power is lost along the wires between transformers: the
farther it travels and the thinner the poles carrying it, the more is lost. Transformers also
lose a little of what passes through them, plus a small constant core loss. Every loss is burned
by a hidden consumer, so it shows in the electric network statistics and loads your power plants
like any other demand.

Q: What do I need to set up?
A: Factorio 2.1 and Power Overload 2.3.3 or later. Set Power Overload's "Transformer efficiency"
map setting to 1 (100%). This mod charges transformer inefficiency itself, at its own
"Transformer efficiency" setting (default 99%). If Power Overload's is lower, this mod's
efficiency is ignored, so the loss is never charged twice, and a one-time warning is shown.

Q: How is a wire's resistance decided?
A: Each pole type has a resistance per tile of wire, from its Power Overload power rating:
r = sqrt(P_big / P_pole). With the default ratings:
Huge electric pole 0.32
Big electric pole 1
Substation 1.5
Medium electric pole 2.24
Small electric pole 5.5
Fuses count as the pole they protect. A wire between poles A and B costs
length x (r_A + r_B) / 2. Each pole's tooltip shows its value as "Line resistance".

Q: How far is "far"?
A: For each transformer the mod finds the shortest path along copper wires from its output to every
pole and every downstream transformer on the network it feeds. Distances are resistance-weighted,
in tiles of big-pole wire: 100 tiles of small poles count as about 550. The search stops at other
transformers; it does not pass through them.

Q: How is the loss calculated?
A: A route loses "Line loss per tile" (default 0.025%) times its distance, capped at 95% per route,
so at least 5% of the power on any route arrives. A transformer pays the average of its routes'
losses, weighted by the power on each route:
- downstream transformers count with the power they actually draw;
- machines (anything powered directly by the network: assemblers, lamps, accumulators
charging...) are spread over the network's poles, because the game does not say which pole
powers which machine.
Example: 100 tiles of big poles lose 2.5%; the same run on small poles about 14%.

Q: Where is each loss burned, and where do I see it?
A: Each transformer gets two hidden consumers, listed by name in the electric network statistics:
"Line loss" on its downstream network (the one it feeds): its line loss x its output.
"Transf. ineff." on its upstream network (the one it draws from): its inefficiency,
drawn x (1 - e) / e, plus its core loss.
A transformer fed directly by generators gets a second "Line loss" consumer, on that generator
network, for the wires between the generators and the transformer.
The transformer panel (open a transformer) shows its upstream line loss (of the power arriving at
it), its downstream line loss (on the network it feeds), its inefficiency and its core loss.
Hovering a transformer shows the power it draws and its upstream line loss.

Q: What is the core loss?
A: A switched-on transformer burns a constant 0.1% of its rating (setting), even with no load, like
the core of a real transformer. A transformer is rated by the weaker of its two sides: the
highest-rated pole wired to each side (quality included), and the smaller of the two. A step-up
at a power plant (medium poles into a huge trunk) and a step-down from a huge trunk to medium
poles are both rated at the medium pole's 60 MW, so they lose 0.06 MW each. A switched-off
transformer loses nothing.

Q: Several transformers feed the same network. Who pays for what?
A: With "Feed nearest consumers first" on (the default), each transformer's power goes mostly to the
consumers nearest to it. The flows are balanced so that every transformer delivers what it was
measured to deliver and every consumer receives what it draws, each pairing pulled by
1 / distance, as current divides inversely with resistance. Every pole belongs to its
electrically nearest transformer, which pays for the machines on it.
With the option off, every transformer is treated as feeding every consumer in the same
proportions.

Q: A very power-hungry machine sits at the far end of a line. Does it cost more than lamps there?
A: Only with the map setting "Line losses: weight machines by their live load" (off by default). By
default machines count as spread evenly over the network's poles. With the setting on, each pole
is weighted by the machines in its supply area and what that machine type is drawing right now:
a 100 MW machine at the end of 600 tiles of big poles, plus 10 MW of lamps along them, gives a
15.0% line loss instead of 8.3%, and drops back to the lamps' 7.9% while the machine is idle. It
costs extra script time: an entity search per pole each time a network is searched again, which
also happens whenever an electric machine is built or removed.

Q: Does a power-hungry machine need many poles around it to spread its draw?
A: No. With machine weighting on, each machine is counted once, at a single pole: the electrically
nearest pole whose supply area covers it. Its whole draw sits at that pole's distance from the
transformer, however many poles surround it. What lowers its loss is a shorter or
lower-resistance path to that pole (a big or huge pole trunk), or a transformer close to it.

Q: Do parallel wires reduce the loss?
A: No. Distance is the single cheapest path through the wires. In a real grid two lines in parallel
halve the resistance and a mesh of poles spreads the current; here a second, parallel line only
helps if it is itself a cheaper path. Modelling parallel paths would need a full network solve
on every search, which would cost far more script time on large bases, so the mod keeps
shortest paths.

Q: Does it pay to feed a network from several sides?
A: Yes, for spread-out load. Feeding a long network from both ends cuts its machines' line loss by
about a third, as real current division would (not by half: current from each end still reaches
loads on the other side). Each extra transformer costs its core loss, so do not spam them. With
"weight machines by their live load" on, the gain follows where the load actually is: a feeder
next to the big consumers helps a lot, one far from any load barely helps.

Q: Do machines far from the transformer get less power?
A: No. Factorio's networks have no voltage drop: every machine on a network gets the same
satisfaction. The loss is paid at the transformer instead, as extra demand burned by its
"Line loss" consumer.

Q: My transformer is fed directly by generators. Do the wires to them lose power too?
A: Yes. When no other transformer feeds a transformer's upstream network, the mod searches that
network from the transformer outwards and weights each pole by the rated output of the
generators in its supply area (steam engines, turbines, solar panels...). In a long line of steam
engines, the ones farthest from the transformer cost the most. The loss is burned by a
"Line loss" consumer on the generator network and shown as the transformer's upstream line loss
("from its generators"). Each generator is counted once, for the pole nearest the transformer
that reaches it.

Q: Several transformers draw from the same generators. Who pays for which?
A: With "Feed nearest consumers first" on, generators are paired with transformers the same way
transformers are paired with consumers: each generator belongs to its electrically nearest
transformer, and the flows are balanced so every transformer receives its draw, every group of
generators supplies its share of the rated output, and each pairing is pulled by 1 / distance.
A transformer's upstream line loss is the average over the generators actually feeding it. Two
transformers at opposite ends of a long steam field each pay about a quarter less than the
field's overall average. With the option off, each transformer pays the average over every
generator on the network.

Q: What is not charged?
A: Machines powered directly by a generator network, with no transformer in between (lamps hanging
off a steam field, say), and generators wired into a network that a transformer also feeds:
those generators simply cover part of that network's load.

Q: Can you walk through an example?
A: Generator -> T1 -> 300 tiles of big poles -> T2 -> 10 MW of machines along 20 tiles of medium
poles. The generator sits right next to T1, which has big poles on both sides (rated 300 MW);
T2 goes from big to medium poles (rated 60 MW). Default settings. Reading from the generator to
the machines:
Generator output 11.46 MW
T1 core loss (0.1% of 300 MW), at the generator 0.30 MW "Transf. ineff." (T1's)
T1 inefficiency (1%), at the generator 0.11 MW "Transf. ineff." (T1's)
300-tile line (7.5%), between T1 and T2 0.83 MW "Line loss" (T1's)
T2 core loss (0.1% of 60 MW), between T1 and T2 0.06 MW "Transf. ineff." (T2's)
T2 inefficiency (1%), between T1 and T2 0.10 MW "Transf. ineff." (T2's)
Medium-pole wires to the machines (0.56%), after T2 0.06 MW "Line loss" (T2's)
Reaching the machines 10.00 MW
Losses: 1.46 MW, 12.7% of generation.

Q: And with several generators and two branches?
A: Three steam engines G1, G2, G3 (equal output) at 5, 10 and 15 tiles of medium poles from T1
-> 100 tiles of big poles -> T2 and T3 side by side at the end of the trunk:
T2 feeds S2: 30 MW of machines along a long line, 200 tiles of medium poles.
T3 feeds S3: 5 MW of machines along a short line, 20 tiles of medium poles.
T1, T2 and T3 each have medium poles on one side, so each is rated 60 MW. Default settings.

The losses, from the generators to the machines:
G1 + G2 + G3 output (12.97 MW each) 38.92 MW
Generator wires (0.56%), before T1 0.22 MW "Line loss" (T1's, upstream)
T1 core loss + inefficiency, before T1 0.45 MW "Transf. ineff." (T1's)
Trunk, 100 tiles of big poles (2.5%) 0.96 MW "Line loss" (T1's)
T2 core loss + inefficiency, on the trunk 0.38 MW "Transf. ineff." (T2's)
T3 core loss + inefficiency, on the trunk 0.11 MW "Transf. ineff." (T3's)
S2's long line (5.59%) 1.78 MW "Line loss" (T2's)
S3's short line (0.56%) 0.03 MW "Line loss" (T3's)
Reaching the machines (30 + 5) 35.00 MW
Losses: 3.92 MW, 10.1% of generation.

Where the distances come from:
- Generators: their average distance from T1, 10 tiles x 2.24 (medium pole) = 22.4, so 0.56%.
- Trunk: T2 and T3 both sit 100 tiles from T1, so T1 pays 2.5% whatever the split between
them.
- S2 and S3: machines count as spread along their lines, so the average distance is half the
line: 100 x 2.24 = 224 (5.59%) for S2, 10 x 2.24 = 22.4 (0.56%) for S3.
What the panels show:
T1: upstream line loss 0.56% (from its generators), downstream 2.5%.
T2: upstream 2.5%, downstream 5.59%. T3: upstream 2.5%, downstream 0.56%.
S2's long medium-pole line is the biggest single loss. The worst-routes list does not show it,
because it is a machines line, but the heatmap colours its far poles orange (about 11%).
Carrying the power on big poles closer to S2, or feeding S2 from both ends, cuts it.

Q: Are the losses applied instantly?
A: No, there are two delays:
- Inside a transformer (Power Overload): the energy it draws from its upstream network in one
tick is handed to its downstream network in the next tick (t -> t+1).
- Loss burns (this mod): the power each transformer moves is read from the network statistics
once a second and smoothed (each new reading counts 40%). The burns are then set from that
reading and apply from the next tick until the next reading.
So losses follow a change in load within a few seconds, and short spikes are averaged out. The
totals over time are what count.

Q: Does the loss count towards Power Overload's pole limits?
A: Yes. The losses are real demand, so a badly lossy line can overload the poles feeding it.

Q: How do I find where I am losing the most?
A: Turn on the grid diagram (shortcut bar): its panel lists the 5 routes (between transformers, or
from generators to a transformer) that lose the most power, each with a "Show" button that opens the map there. The heatmap (shortcut
bar) colours every pole by the line loss of the power reaching it, from green (under 0.5%) to
dark red (50% and above). "Power lost per pole" (shortcut bar) puts a dot on every pole sized
and coloured by the watts lost delivering the machine load on it: with "weight machines by
their live load" on, a big red dot is a power-hungry machine far from its transformer.

Q: Will it slow my game down?
A: Distances are only searched again when a network changes (a pole built or removed, networks
merged or split, a transformer added or removed), at up to 100 poles per tick, plus a slow
background pass of 10 poles per tick. Power is measured once a second. To check the cost on your
save, enable "show-time-usage" in the debug settings (F4).