Factorio nuclear reactor ratio: heat exchangers and turbines

Every 10 MW of reactor heat needs 1 heat exchanger, and every heat exchanger feeds about 1.7 steam turbines. A 2 × 2 block of four reactors makes 480 MW and needs 48 heat exchangers and 83 steam turbines.

The numbers

• A nuclear reactor makes 40 MW of heat on its own.
• Neighbour bonus: each reactor gets +100% for every working reactor directly next to it. That is why reactors are always built in pairs or blocks.
• A heat exchanger turns 10 MW of heat into steam, and a steam turbine turns that steam into 5.82 MW of power, so 10 ÷ 5.82 ≈ 1.72 turbines per exchanger.
• One uranium fuel cell lasts 200 seconds in a reactor, whether the power is used or not. A reactor with no fuel cell gets no bonus and gives none.

Common layouts

In a 2 × N layout the corner reactors have 2 neighbours (40 × 3 = 120 MW) and the middle ones 3 (40 × 4 = 160 MW). Long double rows are the most fuel-efficient way to grow.

Water and steam

Each heat exchanger uses about 103 water per second and each turbine about 60 steam per second, so one offshore pump (1,200 water per second) supplies about 11 heat exchangers. A 2 × 2 block needs 5 offshore pumps.

Saving fuel

Reactors burn fuel cells even at low demand. Most players buffer steam in storage tanks and only insert a new fuel cell when the steam stored drops below a set level, using a circuit condition on the inserter. That stops a big nuclear plant from wasting uranium at night when solar takes over.

Ready-made plants: nuclear power blueprints.