Subnautica Thermal Plant guide: fragment locations in the Grand Reef, Dunes, Sparse Reef and Jellyshroom Cave, plus the build recipe and best hot spots.
Thermal Plant Subnautica — Recipe, Fragments & Placement
The Thermal Plant is a base power generator in Subnautica that converts ambient heat (>25°C) into energy: output scales linearly with temperature, up to 99 energy per minute at 100°C, with 250 energy of internal storage. You unlock it by scanning 2 fragments in the Grand Reef, the Dunes, the Sparse Reef or the Jellyshroom Cave Degasi base, then build it with the Habitat Builder for 5 Titanium + 2 Magnetite + 1 Aerogel. The single best placement is a Jellyshroom Cave lava geyser (~110°C), which powers a Safe Shallows base indefinitely. This guide covers every fragment location, the recipe, the output math and the wiring.
Here's what you'll learn:
- All Thermal Plant fragment locations, including the easiest early unlock
- The exact recipe and the output formula
- The best heat sources and how to wire power to your base
- Thermal Plant vs Solar, Bioreactor and Nuclear Reactor
Official resources: Steam store page · Official Subnautica Wiki — Thermal Plant · IGN Subnautica page
What Is the Thermal Plant?
The Thermal Plant is an Exterior Module built with the Habitat Builder. It converts nearby heat into energy and displays the local temperature on a small screen. Its output is unlimited in principle — given enough time and proximity to heat, one plant can run a base forever. The math is worth knowing before you place one:
Per the official Subnautica Wiki — Thermal Plant: "The energy output per minute is linear and can be calculated with °C*1.32-33: so zero at 25°C, 33 at 50°C, 66 at 75°C, 77.88 at 84°C and at or above 100°C the energy output reaches the maximum of 99."
Key numbers: output formula energy/min = °C × 1.32 − 33, max 99/min at 100°C+, 250 energy storage per plant.
How to Unlock the Thermal Plant
Scan 2 Thermal Plant fragments — the blueprint is a fragment item, not a databox. Official wiki locations:
| Location | Notes |
|---|---|
| Grand Reef | Seabed fragments and around wrecks |
| Dunes | Seabed fragments (Reaper territory — go in prepared) |
| Sparse Reef | Seabed fragments |
| Jellyshroom Cave | Degasi Seabase — the easiest early unlock, directly under the Safe Shallows |
The Jellyshroom Degasi base is the community-favorite route: it's reachable in the first hour with a Seaglide and a High Capacity O₂ tank, and you're collecting the base's other goodies (including the Alien Containment blueprint) in the same trip. A Steam discussion also reports fragments "commonly near wrecks within the red grassy plateau region" — treat that as an unverified bonus spawn.
Drop a Scanner Room over the Jellyshroom Cave entrance (the glowing openings on the Grassy Plateaus border) and scan for fragments — the orange blips will point straight at the Degasi base pieces. It's the same trick that works for every other fragment hunt; see our Multipurpose Room and Scanner Room guide for the setup.
Thermal Plant Recipe & Energy Rates
The recipe is crafted with the Habitat Builder:
| Ingredient | Count | Where it comes from |
|---|---|---|
| Titanium | 5 | Metal Salvage, Limestone Outcrops |
| Magnetite | 2 | Jellyshroom Cave, Mountains, Lost River — see our Magnetite guide |
| Aerogel | 1 | 1 Ruby + 1 Gel Sack in the Fabricator — see our Aerogel guide |
Several older guides and forum posts list the Thermal Plant at 2 Titanium + 1 Magnetite + 1 Aerogel. The current game files, the official wiki and subnauticamap.io all agree on 5 Titanium + 2 Magnetite + 1 Aerogel — the extra Magnetite is exactly why you farm the Jellyshroom Cave before building your first plant.
Output rates at useful reference temperatures (formula: °C × 1.32 − 33):
| Temperature | Energy / minute |
|---|---|
| 25°C | 0 (threshold) |
| 30°C | 6.6 |
| 50°C | 33 |
| 75°C | 66 |
| 84°C | 77.88 |
| 100°C+ | 99 (max) |
Where to Build It
- Jellyshroom Cave lava geysers — the best spot in the game. Geyser centers reach ~110°C, which pins the plant at max output. The cave is within reasonable range of the Safe Shallows, so a single plant (plus transmitters) runs your main base forever. Lava eruptions don't damage the plant — but the heat can kill you while you place it, so drop it from a distance with the Habitat Builder.
- Inactive Lava Zone / Lava Lakes — extremely hot for endgame bases, but you'll usually power those with the Prawn dock instead.
- Deep Grand Reef vents — moderate output for deep forward bases; watch for the Crabsquid nearby (see our Crabsquid guide).
Placement colors tell you everything: red = can't place here, yellow = buildable but too cold (no power), green = building, will generate power.
Wiring: because the plant must sit outside a seabase near the heat source, connect it with Power Transmitters (crafted for 1 Gold + 1 Titanium). A blue line shows the connection chain — place transmitters in line-of-sight segments from plant to base.
If the Thermal Plant hologram is yellow, you're too far from the heat — it will build but produce nothing. Check the temperature on the plant's screen after placement: anything below 26°C is a wasted slot. Move it closer to the geyser until the hologram turns green.
Thermal Plant vs Other Generators
| Generator | Best for | Limitations |
|---|---|---|
| Solar Panel | Surface bases, early game | ~15/min at the surface, 75 storage, useless below ~100 m, no output at night |
| Bioreactor | Mid-game bases anywhere | Needs feeding with organic fuel; 500 storage |
| Thermal Plant | Deep bases near any heat source | Placement-dependent; needs transmitters for distance |
| Nuclear Reactor | Endgame megabases | Expensive, needs Reactor Rods — see our Nuclear Reactor guide |
The verdict: the Thermal Plant is the best unlimited mid-game power for anything below the sun zone, and the Jellyshroom geyser is the single highest-value power spot on the map — two or three plants there plus transmitters outclass every solar setup and never need feeding. For the endgame Lava Zone base, keep the Power Cell Charger running off one and you'll never swap cells again.
FAQ
Where do I find Thermal Plant fragments in Subnautica?
The Grand Reef, the Dunes, the Sparse Reef and the Jellyshroom Cave (Degasi Seabase). Scan 2 fragments to unlock the blueprint. The Jellyshroom Degasi base is the easiest early source.
What is the Thermal Plant recipe?
5 Titanium + 2 Magnetite + 1 Aerogel, built with the Habitat Builder. Aerogel is made from 1 Ruby + 1 Gel Sack.
How much power does a Thermal Plant make?
It follows the formula °C × 1.32 − 33 energy per minute — zero at 25°C, 33/min at 50°C, and a maximum of 99/min at 100°C+. It stores up to 250 energy.
Where should I build a Thermal Plant?
Beside a Jellyshroom Cave lava geyser (~110°C, max output, close to the Safe Shallows), then chain Power Transmitters back to your base. Deep Grand Reef vents work for forward bases.
Do lava geysers damage the Thermal Plant?
No — eruptions don't damage the plant. The heat can kill you while you're placing it, so build from a distance.
Related Guides
- Subnautica Magnetite — Where to Find It
- Subnautica Aerogel — Recipe and Where to Get Ruby & Gel Sacks
- Subnautica Nuclear Reactor — Setup Guide
- Subnautica Multipurpose Room — Base Building Guide
Last updated: August 13, 2026.
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