Plug Slug

Plug Slug is a critter found in Oxygen Not Included that can be ranch-ridden for power. Unlike most power generators, it does not consume fuel in a building; instead, the critter itself produces electricity while it is awake at night, and also excretes Hydrogen after eating metals. Plug Slugs have three variants: the power-producing Plug Slug, the liquid-handling Sponge Slug, and the gas-handling Smog Slug. The family shares the same diet preferences, but each morph has a different secondary function.

A Plug Slug can eat unrefined metal ores and refined metal. When it does, it produces power and also generates Hydrogen, which can be captured and used in a Hydrogen Generator. Wild Plug Slugs produce up to 400 W, while tamed ones produce up to 1600 W when well fed. Their output drops if they are hungry, to 1200 W below 5000 kcal, 800 W below 3000 kcal, and 40 W when starving. Power output is independent of happiness and other statuses. Over a full night, a well-fed tame Plug Slug can provide about 120 kJ of direct electrical energy, plus enough Hydrogen for another 24 kJ of stored energy, for a total of 144 kJ per critter per day.

Plug Slugs behave very differently from buildings. They can climb walls and walk along ceilings, and during the night they nest on a ceiling and hang down, creating a socket two tiles below the ceiling from which power can be drained. They prefer to plug into exposed wires. Two Plug Slugs cannot sleep on the same tile, and their socket cannot overlap buildings such as Storage Bins. Because they only produce power during the night, their average output over a full cycle is much lower than the peak values suggest.

Their practical use is strongest in wild ranching or in low-infrastructure power setups. Wild Plug Slugs produce free electricity wherever they are brought, and this can be especially useful on planetoids where establishing conventional power is inconvenient. They are also a valid alternative to solar in locations where surface access is not desirable. Since they do not require access to the surface, they can be useful when colonizing asteroid types with heavy Regolith exposure.

The main drawback is resource cost. Plug Slugs consume metals and metal ores, which are valuable construction materials, so maintaining them as a long-term power source is usually less efficient than their raw output implies. They are most useful when the player wants a niche, low-setup source of electricity, or when a ranch is already producing excess metal and Hydrogen handling is not a problem.

A few useful details:

• Plug Slug eggs crack into 1000 g of Raw Egg and 100 g of Egg Shell.
• A dead Plug Slug drops 3200 kcal of Meat.
• Starving Plug Slugs can be fed just before nightfall to greatly improve energy efficiency for that cycle, since their nighttime output is decided when they become drowsy.
• The Super Sustainable achievement is not disabled by using Plug Slugs, and their electricity counts toward its progress.

Plug Slugs can appear on the Swampy Asteroid in the Spaced Out! DLC, where at least five mature individuals may be present. Additional Plug Slugs can also be printed or found in swampy pockets on other asteroids. Their variants are influenced by environment: time spent in unbreathable gas increases the chance of producing a Smog Slug egg, while time spent in liquids increases the chance of producing a Sponge Slug egg.