Powering your structures with solar panels is something very common in Space Exploration. However, once you leave Nauvis, it is not immediately obvious what the generated power will be and how to set up structures to meet your needs.
Space Exploration not only adds additional solar panels and accumulators, but makes use of the game engine to give uniqueness to every location in game.
Each surface has its own characteristics, and there are two that are relevant to solar power: day/night cycle duration, and solar efficiency.
On top of that, harnessing solar energy in space is easier to manage: space surfaces do not have nights, and always have 50% brightness, so instead of generating a variable amount of power depending on the time of the day, they will always generate a constant output.
Note: Nauvis always has 100% efficiency and the vanilla day/night cycle duration.
|Item||Maximum Power Output|
|Solar Panel||60 kW|
|Flat Solar Panel||400 kW|
|Flat Solar Panel 2||800 kW|
|Flat Solar Panel 3||1600 kW|
|Holmium Accumulator||50 MJ|
|Naquium Accumulator||250 MJ|
Solar Power on Planet Surfaces
Calculating the Accumulator/Panel Ratio
The ratio formula is:
R = 0.168 * (MaxPanelOutput kW / AccumulatorCapacity kJ) * CycleDuration s * Efficiency / 100
Which, if using the vanilla panels and accumulators, can be further simplified into this:
R = 0.002016 * CycleDuration s * Efficiency / 100
Note the measurement units.
The planet Efficient has 120% solar efficiency and 9 minutes day/night cycle.
If we want to know the ratio of vanilla accumulators per vanilla panels, we have:
R = 0.168 * (60 kW / 5000 kJ) * 540 s * 120 / 100
R = 0.002016 * 540 s * 1.2
R = 1.3
So when on planet Efficient's surface, we'd have to place roughly 13 accumulators every 10 solar panels.
The high efficiency make it so that we need a smaller number of panels to power the base, but the very long day/night cycle requires many more accumulators to store the charge necessary to last the night.
Calculating the Average Panel Output
This is easy to calculate:
AveragePanelOutput = MaxPanelOutput * 0.7 * Efficiency / 100
The 0.7 constant is applied like in the vanilla game, as the equivalent time of a panel operating at average output is always 70% of a day cycle.
Let's go back to planet Efficient. Having 120% efficiency, our average output for a vanilla panel would be:
AveragePanelOutput = 60 kW * 0.7 * 120 / 100 = 50.4 kW
Given the same efficiency or similar day/night cycle, it's easy to tell which planet is better for solar. However, what if both characteristics are very different or very similar?
Efficiency at first might seem the most important trait, because with more power, the less items one needs, however if the day/night cycle is long enough, the accumulators might actually make things more expensive.
Planet Efficient from the previous examples is actually slightly worse than Nauvis despite the higher efficiency. To generate 4.2 MW, Nauvis requires 100 solar panels and 84 accumulators, while Efficient requires 83.33 panels and 108.33 accumulators.
How not to get tricked then? It's easy. Take the day/night cycle length and divide it by the efficiency. The planet with the lower number wins.
Solar power in space
In space there is no day/night cycle, so there is no need to calculate ratios or average outputs, as panels will have a constant output and won't need to supply power to accumulators for the night.
This constant output is calculated as usual by multiplying the nominal maximum output by the efficiency ratio (MaxPowerOutput * Efficiency / 100).
Note that this already takes into account the fact that in space there is a constant 50% brightness, so this calculated amount is actually 50% of what the game will show as maximum when checking the panel output, and the bonus will not be the same as the efficiency percentage shown in the universe explorer - this is different from what you see planetside where the bonus shown is actually the efficiency percentage minus a hundred.
You can enter the rabbit hole of solar power calculation from the official Factorio wiki by clicking here