Nuclear power is the dense, late-game energy backbone of Factorio — a single reactor block can replace a sprawling field of solar panels or a forest of steam engines, and it scales beautifully thanks to the neighbour bonus. But getting there means taming a uranium supply chain that behaves differently from every other ore in the game. This guide walks through the complete pipeline: mining uranium with sulfuric acid, processing it in centrifuges, enriching scarce U-235 with the Kovarex process, building fuel cells, and laying out reactors, heat exchangers, and steam turbines in the correct ratios. Every number here is drawn from the official wiki tutorial, and the core mechanics are unchanged between Factorio 1.1 and the current 2.0 / Space Age line.
Version context: 2.0, Space Age, and what changed
Factorio 2.0 (the free base-game update) and the paid Space Age expansion both launched on October 21, 2024, and 2.0.x is the current stable line as of 2026. The good news for nuclear engineers: the entire fission system covered below — the 40 MW reactor, the +100% neighbour bonus, fuel-cell math, and Kovarex enrichment — is unchanged from 1.1. Space Age adds a separate, higher-tier fusion reactor system on the frozen planet Aquilo, but that is a distinct technology from the uranium fission covered here. So whether you’re on a vanilla 2.0 server or an expansion playthrough, the reactor build math in this guide holds.
One important caveat for older guides you may find elsewhere: 2.0’s fluid rework changed several power ratios. We’ll flag the big one (steam offshore pumps) in the comparison section so you don’t copy a 1.1-era blueprint that no longer balances.
Mining uranium: why you need sulfuric acid
Uranium ore is the one resource that an ordinary electric mining drill cannot extract on its own. The drill must be fed sulfuric acid as a fluid input, consuming it at a rate of 10 sulfuric acid per 10 ore — exactly 1 sulfuric acid per ore mined. Productivity-bonus ore is free: the extra ore generated by productivity modules does not consume additional acid.
This means your uranium outpost needs a fluid supply line, not just a belt. The standard approach is to produce sulfuric acid centrally (sulfur + iron plates + water via chemical plants) and pipe it out to the mining patch, or to set up a local acid plant. Burner drills will not work here at all — you need electric mining drills with the acid pipe connected. Plan your patch layout around getting acid in as much as getting ore out.
Processing: the brutal ~0.7% U-235 yield
Raw uranium ore goes into a centrifuge, which runs uranium processing: 10 ore every 12 seconds. The output is where nuclear power earns its reputation for patience. On average, every 10,000 ore yields roughly 7 U-235 and 993 U-238 — a U-235 rate of about 0.7%. U-238 is common and used in bulk; U-235 is the rare, precious isotope that powers everything.
That 0.7% figure is why uranium feels slow at first. You can mine ore all day and still be starved for U-235. The solution to that scarcity is the Kovarex enrichment process.
Kovarex enrichment: turning U-238 into more U-235
The Kovarex enrichment process is a research-gated centrifuge recipe that lets you convert your abundant U-238 stockpile into the scarce U-235. The recipe is:
Kovarex enrichment (60 s, in a centrifuge):
INPUT: 40 U-235 + 5 U-238
OUTPUT: 41 U-235 + 2 U-238
Net per cycle: +1 U-235 for -3 U-238The trick is that the 40 U-235 and 2 of the U-238 act as catalysts — they go in and come straight back out. The true exchange per 60-second cycle is a net +1 U-235 in return for −3 U-238. The catch is the activation cost: you must already own 40 U-235 just to start a single centrifuge running Kovarex, which is a significant up-front investment when you’re earning U-235 at 0.7%.
The practical workflow is to bootstrap one Kovarex centrifuge with your first hard-won 40 U-235, then use circuit conditions to insert exactly 40 U-235 + 5 U-238 per cycle and extract the surplus, looping the catalyst back in. Once one centrifuge is self-sustaining, you can fund more, and your U-235 supply becomes effectively unlimited as long as U-238 keeps flowing.
Uranium fuel cells
Reactors don’t burn raw isotopes — they burn uranium fuel cells. The recipe combines a little of the rare isotope with a lot of the common one:
Uranium fuel cell recipe:
1 U-235 + 19 U-238 + 10 iron plate → 10 uranium fuel cells
Each cell stores: 8 GJ
Reactor consumes: 1 fuel cell per 200 sEach cell holds 8 GJ of energy, and a reactor consumes one cell every 200 seconds. Because one batch of the recipe produces 10 cells from a single U-235, a single enriched isotope keeps a reactor fed for over half an hour. This is why the painful early scarcity pays off so dramatically: once U-235 is flowing, fuel becomes almost an afterthought.
A worthwhile efficiency note: spent fuel cells return used-up uranium fuel cells, which can be reprocessed in a centrifuge to recover some U-238 — a closed loop that softens U-238 demand over time. Insert fresh cells and pull spent ones with inserters reading the reactor’s fuel state, and you’ll never waste a cell.
Reactors and the neighbour bonus
A single nuclear reactor produces exactly 40 MW of heat. On its own that’s respectable, but the reactor’s defining mechanic is the neighbour bonus: every reactor gains +100% heating power for each active neighbouring reactor placed directly adjacent to it. The reactors must align fully on the shared side — you place them in a tight, gapless grid for the bonus to apply.
This turns reactor layout into a math problem worth solving, because the bonus compounds dramatically. Consider the classic 2×2 block of four reactors. Each reactor in that block touches two neighbours, granting +200% — so each reactor outputs 3× its base, or 120 MW. Four reactors that would individually make 160 MW instead make:
Lone reactor: 40 MW
2x2 block (4 reactors):
each has 2 neighbours -> +200% -> 120 MW each
4 x 120 MW = 480 MW (vs. 160 MW unbonused)The same logic extends to long 2×N rows — the standard mega-base layout — where interior reactors each touch three neighbours. The more reactors you pack into a contiguous block, the higher the per-reactor multiplier, which is why serious nuclear builds favor one big array over several small ones.
Heat exchangers and steam turbines: the conversion chain
Reactor heat doesn’t generate electricity by itself. It heats a connected network of heat pipes, which feed heat exchangers that boil water into high-temperature steam, which then drives steam turbines to make power. Each link in the chain has a fixed throughput:
- Heat exchanger: transfers 10 MW, heating ~10.3 water/s into ~103 steam/s at 500 °C. It produces nothing until the heat network reaches 500 °C.
- Steam turbine: consumes up to 60 steam/s at 500 °C.
From these two numbers the build ratios fall out cleanly. A lone reactor outputs 40 MW, and each heat exchanger consumes 10 MW — so you need 4 heat exchangers to fully consume one lone reactor. Each exchanger produces ~103 steam/s while each turbine drinks up to 60 steam/s, so you need roughly 1.72 turbines per exchanger (103 ÷ 60), which rounds up to about 1.75 at scale.
| Component | Key rate | Per lone reactor (40 MW) |
|---|---|---|
| Nuclear reactor | 40 MW heat (×neighbour bonus) | 1 |
| Heat exchanger | 10 MW → ~103 steam/s @ 500 °C | 4 |
| Steam turbine | up to 60 steam/s | ~7 (≈1.75 per exchanger) |
That gives the famous beginner build-rule: 1 reactor : 4 heat exchangers : 7–8 turbines, sized before counting the neighbour bonus. Once you add the bonus, you scale the exchangers and turbines up to match the extra heat. For a packed 2×N array, plan for roughly 16 heat exchangers and ~27.5 turbines per 16 exchangers per interior reactor’s bonused output. The simplest rule of thumb: build the 1:4:7 ratio first, then multiply the exchanger/turbine side by each reactor’s bonus multiplier.
Buffering heat for steady output
Because reactors consume fuel in discrete 200-second chunks, a naive setup wastes energy whenever heat overshoots. The standard fix is to run the heat network up to its maximum temperature and let the heat pipes themselves act as a thermal buffer, only inserting a new fuel cell when reactor temperature drops below a threshold (read with a circuit wire). This keeps the array near peak output without burning cells while the network is already saturated — the nuclear equivalent of accumulators smoothing a solar grid.
Nuclear vs. steam and solar: when to switch
Nuclear is dense and fuel-cheap once running, but it’s not the only option, and the right choice depends on your stage. Here’s how the three main grids compare — including the one ratio that changed in 2.0 and trips up players following old guides.
| System | Core ratio / figure | Notes |
|---|---|---|
| Boiler steam (1.1) | 1 offshore pump : 20 boilers : 40 engines (≈40 MW) | Outdated — do NOT use on 2.0 |
| Boiler steam (2.0) | 1 offshore pump : 200 boilers : 400 engines (≈360 MW) | 2.0 pump now outputs 1200 water/s |
| Boiler : engine | 1 : 2 (unchanged) | One boiler feeds two steam engines |
| Solar : accumulator (Nauvis) | 25 panels : 21 accumulators (~0.84 each) | Nauvis-only; other planets differ |
| Nuclear (per lone reactor) | 1 reactor : 4 exchangers : ~7 turbines | Scale up by neighbour bonus |
The 2.0 offshore-pump warning: in 1.1 the optimal steam ratio was 1 pump : 20 boilers : 40 engines for about 40 MW. The 2.0 fluid rework boosted the offshore pump to 1200 water/s, and since water-to-steam is 10:1, the new optimal ratio is 1 pump : 200 boilers : 400 engines for roughly 360 MW. If a guide tells you 1:20:40, it’s a 1.1-era guide. The 1 boiler : 2 engine sub-ratio, however, is unchanged. For the full breakdown of every power source, our comprehensive guide to power management in Factorio covers brownouts, accumulator buffering, and the power-switch backup circuit in detail.
The progression most players follow: boiler steam to bootstrap, solar + accumulators (the confirmed 25:21 Nauvis ratio) for a clean mid-game grid, then nuclear once you need raw density and have uranium flowing. Note that the 25:21 solar ratio is Nauvis-specific — Vulcanus, Fulgora, and the other Space Age planets have different day lengths and solar multipliers, so don’t copy it across worlds.
Defending your reactor and feeding it reliably
A uranium outpost and a reactor array are both high-value targets. Uranium patches are often far from your main base, deep in biter territory, so your acid pipeline and ore belts pass through contested ground. Pollution from centrifuges and the rest of your factory raises the evolution factor and draws attacks, so wall off the mining patch and keep turrets fed. Our detailed guide to dealing with biters breaks down evolution drivers and turret choices, and you’ll want construction and logistic robots auto-repairing walls with stocked repair packs so a stray spitter doesn’t open a hole in your defenses overnight.
For supply reliability, most large nuclear builds use a train to haul raw uranium ore from the patch to a central processing area, and to deliver finished fuel cells out to remote reactor stations. Trains keep the dense, slow uranium chain flowing without belt sprawl across the map.
If you’re running a dedicated multiplayer factory, a stable host matters when your whole team’s progress hinges on a single reactor array humming along. Renting a managed Factorio server keeps your base online 24/7 so construction bots keep repairing and centrifuges keep enriching even when you’re offline — and our step-by-step Factorio server setup documentation walks through getting a save running on dedicated hardware.
Frequently asked questions
Why does my mining drill need sulfuric acid?
Uranium ore is the only ore that requires a fluid to mine. An electric mining drill on a uranium patch must be piped sulfuric acid and consumes 1 sulfuric acid per ore (10 acid per 10 ore). Without a connected acid supply, the drill produces nothing. Productivity-bonus ore is free and consumes no extra acid.
How much U-235 do I get from uranium ore?
Centrifuge processing runs 10 ore every 12 seconds and yields about 0.7% U-235 — roughly 7 U-235 and 993 U-238 per 10,000 ore. U-235 is deliberately scarce, which is why the Kovarex enrichment process exists to convert your surplus U-238 into more of it.
What is the Kovarex enrichment ratio?
Kovarex takes 40 U-235 + 5 U-238 and returns 41 U-235 + 2 U-238 over 60 seconds. The 40 U-235 act as a catalyst, so the real result is a net +1 U-235 for every −3 U-238 per cycle. You need 40 U-235 banked just to start one centrifuge running it.
What is the reactor-to-exchanger-to-turbine ratio?
A lone 40 MW reactor pairs with 4 heat exchangers and about 7 steam turbines (each exchanger needs ~1.75 turbines). Use 1:4:7 as your base unit, then scale the exchanger and turbine counts up to match the extra heat from the neighbour bonus when reactors are packed together.
How does the reactor neighbour bonus work?
Each reactor produces 40 MW base and gains +100% heating power per adjacent active reactor. In a 2×2 block every reactor touches two neighbours (+200% each → 120 MW each), so four reactors output 480 MW instead of 160 MW. Reactors must sit in a tight, fully-aligned grid for the bonus to apply.
Is nuclear power different in Factorio 2.0 / Space Age?
No — uranium fission (reactors, neighbour bonus, fuel cells, Kovarex) is unchanged from 1.1. Space Age adds a separate fusion reactor system on the planet Aquilo as a distinct, higher-tier technology. The one related ratio that did change is conventional steam power: the 2.0 offshore pump now outputs 1200 water/s, shifting the optimal ratio to 1 pump : 200 boilers : 400 engines.
With acid-fed mining, a self-sustaining Kovarex loop, and a properly bonused reactor array feeding the right number of exchangers and turbines, nuclear becomes the most maintenance-free power source in the game. Build the 1:4:7 unit, pack your reactors tight for the bonus, buffer your heat, and your factory will never brown out again. For more Factorio systems mastery, see our full guides on mastering train systems to keep that uranium flowing.
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