Electric charge

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Electric charge
Density None
Transferable Yes
Tweakable Yes
Drainable No
Flow mode Everywhere
Cost None
Since version 0.18

Electric charge, also called electricity or energy, is a resource that is needed to operate various parts in the game. It is critical for unmanned spacecraft, which are generally uncontrollable without any electric charge. However, manned spacecraft usually also need some electricity, mainly for reaction wheels.


Type Name Output Usage
Rocket engines LV-T30 Liquid Fuel Engine 7.0 ⚡/s 1.691 Units of fuel/⚡
LV-T45 Liquid Fuel Engine 6.0 ⚡/s 1.835 Units of fuel/⚡
Toroidal Aerospike Rocket 5.0 ⚡/s 1.828 Units of fuel/⚡
LV-N Atomic Rocket Motor 5.0 ⚡/s 0.3055 Units of fuel/⚡
Rockomax "Poodle" Liquid Engine 8.0 ⚡/s 1.436 Units of fuel/⚡
Rockomax "Skipper" Liquid Engine 10.0 ⚡/s 3.782 Units of fuel/⚡
Rockomax "Mainsail" Liquid Engine 12.0 ⚡/s 7.715 Units of fuel/⚡
Kerbodyne KR-2L Advanced Engine 12.0 ⚡/s 11.176 Units of fuel/⚡
S3 KS-25x4 Engine Cluster 12.0 ⚡/s 15.102 Units of fuel/⚡
Jet engines Basic Jet Engine 4.0 ⚡/s 0.0239 Units of fuel/⚡
TurboJet Engine 5.0 ⚡/s 0.0716 Units of fuel/⚡

Engine alternators

Many rocket and jet engines have alternators installed which produce electricity. The exact output varies based on the throttle level, and engines not running will not produce any electricity. The adjacent table shows the engines which provide electricity, their production at full throttle and fuel usage in vacuum. Jet engines only generate electricity when supplied with intake air.

Solar panels

A solar-powered satellite

Solar panels are a lightweight source of electrical energy. However, they need direct sunlight to work, so they won't produce electricity on the night side of a planet, in the shadow of a spacecraft or during eclipses of the sun, although the craft is illuminated while in an eclipse. Due to this unreliability, it is recommended to have some energy storage as a buffer when supplying a craft solely with solar panels.

All panels, except for the OX-STAT Photovoltaic Panels and the OX-STAT-XL Photovoltaic Panels, need to be extended using the right-click menu (Extend Panels option, and for the retraction choose the Retract Panels) or action groups (using the Toggle Panels command, the player can extend and retract several solar panels with a single keystroke) before they will generate energy. Unpacked solar panels are very fragile and will easily break off when colliding or experiencing atmospheric drag, so they must be retracted during liftoff, aerobraking, or atmospheric re-entry. Note that, as of version 1.0, the unshielded OX-4 series solar panels can't be retracted once deployed, so they are not suited for aerobraking missions.

The energy output of solar panels depends on their orientation to Kerbol. Except for the surface-mounted OX-STAT Photovoltaic Panels (and its larger brother OX-STAT-XL Photovoltaic Panels, all panels will automatically pivot around one axis to face the sun as much as possible. Reorienting a vessel to manually aim the panels at the sun and eliminate shadows cast on them will also improve power generation.

Generated power will also decrease with increasing distance from Kerbol, following the real-life inverse-square law:

Distance (Gm) Power (%) Comment
5.263 668 Moho's semi-major axis
9.832 191 Eve's semi-major axis
13.600 100 Kerbin's orbit
20.726 43.1 Duna's semi-major axis
40.839 11.1 Dres's semi-major axis
68.774 3.91 Jool's semi-major axis
90.119 2.28 Eeloo's semi-major axis
136 1.00 50% farther than Eeloo
430 0.10 Very very far away

There are currently 11 solar panels in-game

Image Part Radial size Cost
Max. Temp.
Electricity per mass
Fuel consumption
(Units of fuel/s)
Gigantor XL.png
Gigantor XL Solar Array Radial mounted 3 000 0.3 1 200 8 50 24.4[Note 1] 81.33
OX-4W 3x2 Photovoltaic Panels Radial mounted 380 0.0175 1 200 8 50 1.64[Note 1] 93.71
OX-4L 1x6 Photovoltaic Panels Radial mounted 380 0.0175 1 200 8 50 1.64[Note 1] 93.71
OX-10C front deployed.png
OX-10C Photovoltaic Panels Radial mounted 1 200 0.09 1 200 8 50 8.25[Note 1] 91.66
OX-10L front deployed.png
OX-10L 1x5 Photovoltaic Panels Radial mounted 1 200 0.09 1 200 8 50 8.25[Note 1] 91.66
SP-W 3x2 Photovoltaic Panels Radial mounted 440 0.025 2 000 8 50 1.64[Note 1] 65.60
SP-L 1x6 Photovoltaic Panels Radial mounted 440 0.025 2 000 8 50 1.64[Note 1] 65.60
SP-10C deployed.png
SP-10C Photovoltaic Panels Radial mounted 1 400 0.13 2 000 8 50 8.25[Note 1] 63.46
SP-10L deployed.png
SP-10L 1x5 Photovoltaic Panels Radial mounted 1 400 0.13 2 000 8 50 8.25[Note 1] 63.46
OX-STAT Photovoltaic Panels Radial mounted 75 0.005 1 200 8 50 0.35[Note 1] 70.0
OX-STAT-XL Photovoltaic Panels.png
OX-STAT-XL Photovoltaic Panels Radial mounted 600 0.04 1 200 8 50 2.80[Note 1] 70.0
  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Energy output depends on the distance and angle to the Sun. The value is achieved at Kerbin's distance, with the panel pointed directly at the Sun.

Radioisotope thermoelectric generator

The PB-NUK Radioisotope Thermoelectric Generator is a constant and reliable source of energy that doesn't require any sunlight and is much more resistant to atmospheric drag than solar arrays. Unfortunately, it has a very impractical shape and is significantly heavier than solar panels with a comparable output of electricity.

Fuel cells

The fuel cell, like the Fuel Cell and Fuel Cell Array, converts liquid fuel and oxidizer directly into electric charge, similarly to generators. As now the electricity production is the only purpose: they consume 0.0025 units of fuel for each electric charge unit (0,0025 Units of fuel/⚡), means they produce 400 units of electricity from a single unit of fuel.

Launch clamps

TT18-A Launch Stability Enhancers provide the attached craft with 1.0 charge units per second per clamp and thus prevent running out of energy on the launch pad.


Storing electric charge helps a craft survive longer without energy supply, deal with peak loads (like transmitting science results) or bridge time gaps when solar panels aren't usable. The following parts store energy:

  • Unmanned command modules such as the Stayputnik Mk. 1 and Probodobodyne RoveMate offer very low capacities and constantly consume energy.
  • Manned command modules offer significant storage capacities and do not consume energy (unless when reaction wheels or SAS are used) but are relatively large and heavy and put Kerbals at risk.
  • Batteries are small and offer high storage capacities at the same time. All have the same capacity/mass ratio of 50 g/⚡ or 20 ⚡/kg.
  • Fuel Cells also store a modest amount of electric charge in addition to their fuel to electricity conversion function.

All energy storage modules on a craft are fully loaded at launch by default.

Consumption and requisition

  • Unmanned command modules constantly use 1.7 or 3.0 units of electric charge per minute and can only store enough internally for a few minutes of operation.
  • Reaction wheels, both the stand-alone parts and as part of command capsules, consume energy while operating.
  • In science and career modes, antennae require large amounts of energy for a short time when they transmit science to the space center.
  • Electric lights and environmental sensors use small quantities of electricity when switched on.
  • Ion engines and rover wheels require particularly large amounts of electricity to operate.

If an unmanned craft has no electric charge available, it becomes entirely nonfunctional and no parts may be operated (notably, this includes motorized solar panels which might have allowed it to recover). However, it can still be saved if another craft docks to it and supplies it with electricity (using either a docking port or an Advanced Grabbing Unit) or if a kerbonaut on EVA manually extends the solar panels. This is why it is good design practice to always include at least one surface mount solar panel or a RTG.


  • Added display name
  • Added abbreviation (used in KerbNet)
  • Changed flowMode from ALL_VESSEL to STAGE_PRIORITY_FLOW
  • Added hsp value (heat capacity)
  • Added cost
  • Resource is now tweakable in the VAB/SPH
  • Initial release