Solar panels and accumulators

The two numbers everything rests on

Entity	Statistic	Value
Solar panel	Peak production	60 kW
Accumulator	Buffer capacity	5 MJ
Accumulator	Charge and discharge limit	300 kW

The discharge limit is the statistic people skip, and it bites in practice. One accumulator releases at most 300 kW, which is 5 panels' worth of peak output. A bank sized purely by stored energy can hold plenty of joules and still fail to deliver them fast enough on a heavy night.

Why the ratio is about darkness, not about panels

A panel produces at full rate in daylight, tapers through dusk and dawn, and produces nothing at night. Accumulators exist to carry the factory across that dark stretch. So the ratio answers one question: how much energy must be banked during the day to survive the night, divided by how much one accumulator holds.

Neither term in that division is a panel statistic. Change the length of the night and the ratio changes, even though the panel and the accumulator are unchanged. That is exactly what happens when you leave Nauvis.

Every planet produces a different amount

Each surface carries its own solar figure. A panel on Vulcanus is the same panel, sitting closer to the sun. Relative to Nauvis:

Planet	Solar figure	Relative to Nauvis	Panel peak output	Panels per 1 MW
Vulcanus	600	2.00x	120 kW	8.33
Nauvis	300	1.00x	60 kW	16.7
Gleba	200	0.67x	40 kW	25.0
Fulgora	120	0.40x	24 kW	41.7
Aquilo	60	0.20x	12 kW	83.3

The spread is wider than most planning accounts for. Vulcanus returns 2x what Nauvis does, so a solar field sized by Nauvis habits is oversized by half there. Aquilo sits at 0.20x, needing 10 times as many panels as Vulcanus for the same megawatt — which is a large part of why solar is not the default answer out there.

Sizing a bank without the memorised number

Rather than carrying one ratio around, the sizing question decomposes cleanly:

1. Take the average load the factory must hold through the night, in watts.
2. Multiply by the length of the dark stretch in seconds. That is the energy to bank, in joules.
3. Divide by 5 MJ for the accumulator count.
4. Check the discharge limit separately: accumulator count multiplied by 300 kW must exceed the night-time load, or the bank cannot deliver what it holds.

Step four is the one the memorised ratio hides. On Nauvis with a typical load the two constraints land close together, so a single number appears to work. On a surface with a different day length, or a factory with a spiky load, they separate and the stored-energy figure alone becomes misleading.

When the discharge limit becomes the binding constraint

Most players size an accumulator bank by stored energy alone: multiply night-time load by darkness duration and divide by 5 MJ. That answers whether the bank holds enough joules. It does not answer whether the bank can release them fast enough.

Each accumulator discharges at 300 kW. Five accumulators can hold 25 MJ, but they can only push 1.5 MW through their output terminals simultaneously. A factory drawing 5 MW overnight would brown out despite having 25 MJ in reserve, because the bank cannot empty fast enough.

Factory night load	Min accumulators for discharge flow	What this means
1 MW	4	Flow is rarely the constraint at this scale.
5 MW	17	Flow is rarely the constraint at this scale.
10 MW	34	A storage-sized bank usually clears this, but verify after expanding.
20 MW	67	A storage-sized bank usually clears this, but verify after expanding.
50 MW	167	Large solar fields often need extra accumulators purely for throughput.
100 MW	334	Large solar fields often need extra accumulators purely for throughput.

The two constraints cross at a specific night length. An accumulator holds 5 MJ and releases at 300 kW, so it empties from full in 16.7 seconds. If your factory's dark stretch is shorter than that, the discharge limit is the binding constraint and you may need more accumulators than the energy calculation suggests. If the dark stretch is longer, storage dominates and the memorised ratio works.

The practical check is simple: after sizing by energy, multiply your accumulator count by 300 kW and compare it to your peak night-time draw. If the number is lower, add accumulators until it is not. The extra units cost iron and space, not fuel or pollution.

Where solar is primary and where it is backup

The per-planet panel output table tells you how many panels a megawatt costs, but the number that decides whether solar is your main power source is the land and panel count relative to alternatives. A planet where a megawatt needs 8 panels is a different proposition from one that needs 83.

Planet	Panels per 1 MW	Role	Practical implication
Vulcanus	8.33	Primary power	Half the panel count of Nauvis for the same output. Solar fields are compact; accumulators still follow the same dark-period math.
Nauvis	16.7	Primary (standard)	The baseline. Solar is a viable primary source with a panel field sized to average output across the full day-night cycle.
Gleba	25.0	Viable, land-intensive	Solar works but the field footprint grows considerably. Most bases pair it with another source rather than relying on it alone.
Fulgora	41.7	Backup or supplement	The panel count for meaningful output is prohibitive. Solar is best used as a supplement or for low-drain outposts, not the main grid.
Aquilo	83.3	Backup or supplement	The panel count for meaningful output is prohibitive. Solar is best used as a supplement or for low-drain outposts, not the main grid.

The ratio between extremes is worth stating directly: Aquilo needs 10 times as many panels as Vulcanus for the same megawatt of peak output. That is not a rounding difference. It is why a blueprint that powers a Vulcanus base comfortably leaves an Aquilo base starved when copied planet to planet without adjusting the panel count.

Note that the accumulator side does not scale with the planet's solar figure. Accumulator capacity and discharge rate are the same everywhere. What changes is how many panels you need to charge those accumulators during daylight, which is the next question.

Charging: the constraint the panel count hides

Sizing panels by average load assumes the daylight surplus is enough to refill every accumulator before dusk. The surplus depends on how much excess panel output exists beyond the factory's daytime draw, and on how long daylight lasts. The table below shows how many Nauvis-equivalent panels it takes to charge one accumulator from empty in a given number of seconds.

Charging window (seconds)	Charging power required	Nauvis panels per accumulator
60	83.3 kW	1.39
120	41.7 kW	0.69
180	27.8 kW	0.46
240	20.8 kW	0.35
300	16.7 kW	0.28

On high-solar planets these numbers drop by the same factor as panel output (Vulcanus needs half as many), but the structure of the problem does not change: your panel field must produce enough surplus above daytime demand to refill the bank, and a shorter charging window means more surplus panels. If you size purely by average output, you may find that the factory runs fine during the day but accumulators never reach full charge before nightfall.

This is also why the four-step procedure below asks for average load rather than peak: solar is inherently an averaging system. Panels do not respond to demand spikes. If your factory has a burst load (laser turrets, radar sweeps, artillery), accumulators must cover the spike regardless of whether it is day or night, which adds a third sizing constraint beyond energy storage and discharge flow.

A worked sizing example

The four-step procedure is clear in the abstract. Here is what it looks like with concrete numbers for a mid-game Nauvis base drawing a steady 10 MW.

1. Average night-time load. Assume the factory draws a steady 10 MW (10,000 kW) through the dark period.
2. Energy to bank. Suppose the dark stretch is approximately 42 seconds. The bank must hold 10 MW × 42 s = 420 MJ.
3. Accumulator count by storage. Divide by 5 MJ per accumulator: 420 / 5 = 84 accumulators.
4. Discharge flow check. 84 accumulators × 300 kW = 25.2 MW, which comfortably exceeds the 10 MW load. The flow constraint is not binding here.

Now consider the same factory on Fulgora, where a panel produces 40% of its Nauvis output. The accumulator count does not change — the load and the dark period are the same. What changes is the panel count: you need 2.5 times as many panels to generate the same surplus for charging. If you built 200 panels on Nauvis and copied the blueprint to Fulgora, the factory would run during the day but accumulators would never fully recharge, because only 80 panels' worth of charging capacity is present where 200 were needed.

The reverse holds on Vulcanus. A Nauvis-sized panel field produces twice the surplus, charging accumulators faster than necessary. This is not harmful — excess panel output is simply not used — but it means a blueprint copied from Nauvis is overbuilt by a factor of two on Vulcanus. The savings in panel count can be redirected to accumulators or to expanding the factory.

Burst loads add a third constraint

The worked example above assumes a steady load. Real factories have bursts: laser turret volleys, radar sweeps, artillery auto-targeting, even a large train arriving at a station. A burst of 30 MW for two seconds draws 60 MJ, but the more demanding requirement is the instantaneous 30 MW flow rate.

A bank sized for 10 MW steady load — 84 accumulators — can deliver 25.2 MW, not 30. During a laser barrage, voltage would sag even though total stored energy is sufficient. The fix is to add accumulators until the discharge flow rate exceeds the burst peak, regardless of what the energy calculation says. This is why large military outposts often have visibly oversized accumulator banks: they are sized for the instant a biter wave hits, not for the average night.

There is no formula in the prototype data for how often bursts occur or how long they last — those depend entirely on factory design and biter activity. The two data-backed constraints (storage and flow) define the minimum bank; burst coverage is a judgement call built on top of them.

Solar versus nuclear as base load

The numbers on this page describe solar in isolation, but the practical question for most players is whether to build a solar field or a reactor block. Both ultimately answer "how do I power my factory", and they have different scaling curves.

Solar scales linearly: every panel adds 60 kW on Nauvis at peak, every accumulator adds 5 MJ of storage and 300 kW of flow. There is no economy of scale — the 10,000th panel costs as much iron as the first. The upside is zero fuel cost, zero pollution, and zero active management once built. A solar field that can power a megabase is very large, but it is also entirely passive.

Nuclear scales with the neighbour bonus. A single reactor produces 40 MW; a 2 by 8 block produces 2,400 MW from 16 reactors, which is 3.75 times the output of 16 isolated reactors. The fuel chain requires active management — uranium mining, centrifuging, Kovarex enrichment — but the physical footprint per megawatt is far smaller than solar. The crossover point depends on how much land a player is willing to cover in panels, and on the planet's solar figure.

On Vulcanus, where a panel produces 120 kW at peak, solar is competitive with nuclear at medium scales. On Aquilo, at 12 kW per panel, the same megawatt requires ten times the footprint, and nuclear becomes the obvious primary source regardless of factory size. The planet's solar figure does not change the reactor's output — nuclear is the same everywhere — so the relative attractiveness of solar shifts planet to planet while nuclear stays constant.

One final note on accumulator placement: like solar panels, accumulators perform identically on every planet. The 5 MJ buffer and 300 kW flow limit are properties of the entity, not the surface. Moving from Nauvis to Aquilo changes how many panels you need to charge the bank, but never how many accumulators the bank itself requires. That separation — panels scale with solar figure, accumulators scale with load and darkness — is the core reason the ratio cannot be reduced to a single number that works everywhere.

Applies when…

• Panel output figures are peak values in full daylight. Average output across a full cycle is lower, and depends on the surface's day length.
• The per-planet figures come from each planet's solar statistic in the prototype data. Space platforms use a separate figure that varies with distance from the sun and is not covered here.
• Day length is a map setting rather than a prototype value, so this page states the sizing procedure rather than quoting a single ratio.
• Accumulator charge and discharge limits apply per accumulator, not to the bank as a whole.

Related

• Production Ratio Calculator — how much power a production line actually draws
• All ratio pages