Factorio Forums

I have a small electric network with 3 x beacons (no modules), 1 x chemical plant, 1 x steam turbine. The network runs on an isolated, disconnected substation. There are no other power poles or substations in the vicinity. The image shows a fourth beacon, that I add later.
The steam turbine produces max 1.8 MW at 165 °C.

The beacon consumes 480 kW (1.440 total).
The chemical plant consumes about 15 kW.

The steam turbine produces exactly the required amount of power (100% satisfaction), which is roughly 1.5 MW.
Now, when I drop a fourth beacon (see image above), the power demand should increase to about 1.9 MW. The turbine should now produce it technical maximum of 1.8 MW, leaving satisfaction at 95%. However, satisfaction drops to 18% due to a sudden jump of power demand of 9.8 MW, and I don't understand where this demand comes from. It also absolutely kills the productivity, because the machines work much slower at 18% productivity, instead of a theoretical productivity of 95%. The graph does not show where the demand comes from.
What is going on?

Many machines, but especially roboports (and apparently Beacons) have an internal energy buffer. Provided that the buffer is full, they only use the amount of power shown. But when they get less than the amount desired, they draw on that buffer, and when it goes, they get REALLY hungry for power to refill that buffer.

In other words, some machines you can get by operating on low power. Others, you want to avoid low power at almost all costs.

That's cool and all, but which of my machines do have a buffer? Where's the problem in my case?

Every machine using electric energy has an energy buffer. It's an important part of how the game engine works with electric power. While processing one tick, and the game engine is processing all machines, all machines consuming electric power pull their energy from their buffer to operate. In a second step in the same tick, the game engine refills the buffer from the electric network. If the buffer can be refilled completely, the small progress bar on mouse hover popup on the right side of the screen is green and you never notice it was emptied and filled again. If not, it is yellow and the fill state is less than 100%. If the fill state of the buffer is less than the energy demand of the machine in this tick, the machine isn't doing anything. If the buffer refills more the next tick, and it is now full enough for the machine, the machine works for this tick. This is the mechanics how the slowdown during a brownout is created.

Somewhere it's written how large this buffer is. It is as big that a machine is able to work for at least one tick in full operating state, as far as I remember. Certain machines, for example the roboport and the laser turret have a bigger buffer, so they can recharge bots from it or shoot. The beacons have huge energy demand, so their buffer is somewhat large.

In general, you don't need to be concerned about this temporary huge power draw if you add a new machine with a big buffer. As long as the average consumption and drain is lower than production, the buffers will get filled eventually after a few seconds. However, all other machines in the network may be working slower as in a brownout during this short period.