Solar Power

Solar power is a great way to provide electricity for your base, without needing to worry about boilers or nuclear reactors running out of fuel, or pollution causing biter attacks. 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 tiers of 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.

Harnessing solar energy in space is easier to manage than the surface of a planet or moon. Space surface do not have nights, and always have specific brightness relative to distance from a star, 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.

Solar energy is also the first way of powering personal equipment in your armor's equipment grid, and is especially effective for armors worn in space.

Structures & Equipment

Solar Panels

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
Portable Solar Panel	30 kW

Accumulators

Item	Capacity	Charge Rate	Discharge Rate
Accumulator	5 MJ	0.25MW	0.5MW
Holmium Accumulator	50 MJ	0.5MW	5MW
Naquium Accumulator	250 MJ	2.5MW	25MW
Personal Battery	20 MJ
Personal Battery Mk2	100 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.

Example:

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.

Example:

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

Comparing Planets

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 buildings 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 in Universe Explorer by the efficiency ratio (MaxPowerOutput * Efficiency / 100).

See Also

You can enter the rabbit hole of solar power calculation from the official Factorio wiki by clicking here