Factorio steam power: the boiler-to-engine ratio

The numbers behind the ratio

A normal-quality boiler produces up to 60 units of steam per second. A normal-quality steam engine consumes up to 30 units per second at its maximum effective temperature of 165°C. Dividing the boiler's output by the engine's consumption gives two engines per boiler.

Component	Normal-quality capacity	What to plan around
Boiler	60 steam/second; 1.8 MW heat output	Enough steam for two engines at full load
Steam engine	30 steam/second; 900 kW electrical output	Each engine adds up to 0.9 MW
One boiler and two engines	Up to 1.8 MW electricity	Requires uninterrupted fuel, water and connections

These are maximum operating figures. Steam engines automatically reduce their consumption and production when the network needs less electricity. Low output on an idle factory is not, by itself, a fault.

Build and check the complete chain

1. Supply water to the boiler's water connection. Check the entity's fluid information instead of assuming that a pipe drawn nearby is connected.
2. Keep the boiler supplied with a compatible fuel. A boiler without fuel cannot keep producing steam.
3. Connect the boiler's steam output to two steam engines. Use the fluid connections shown when placing each machine.
4. Place electric poles so their supply areas cover the engines and the machines you want to run. The poles must also form a connected network.
5. Add a real load, then inspect the boiler, the engines and a pole. Confirm that steam reaches the engines and that electricity reaches the factory.

If something stops along this chain, adding more engines at the end will not repair the missing input. Use the power troubleshooting guide to distinguish an input problem from a capacity problem.

Size a bank for your actual demand

For 9 MW of demand, ten normal-quality steam engines provide exactly 9 MW of capacity. Five boilers can supply those engines at full output.

If you want 20% extra capacity for that same 9 MW load, the target becomes 10.8 MW. That means twelve engines and six boilers. The extra capacity is a planning choice; it does not create fuel or water reserves.

Use the steam power calculator to enter demand and a capacity margin. It rounds engines up to a whole machine, then rounds boilers up to the number needed to support them. Odd engine counts are valid: the last boiler simply has room to support a second engine later.

Why older pump ratios can mislead

Do not extend the boiler-to-engine ratio into an offshore-pump layout without checking your version. The current Factorio Wiki power-production page lists 1 offshore pump : 200 boilers : 400 steam engines. Older layouts commonly quote 1:20:40.

That difference is large enough to make an old diagram a poor reference for current supply planning. Our calculator deliberately leaves out pumps, pipe networks and fuel logistics. Use the linked wiki for the version you are playing and confirm fluid delivery in your own setup.

Quality and mods change the assumptions

This guide covers normal-quality machines with the listed statistics. Quality can change machine performance, and mods may change the entire production chain. Check an entity's displayed statistics before copying the ratio into a modified or mixed-quality setup.

Steam turbines are a different planning problem. This guide is about boilers and steam engines; it does not size nuclear reactors, heat exchangers, turbines or steam storage.

Do I always need more engines when output looks low?

No. First compare supply and demand in the electric-network information. A lightly loaded system does not need to produce its theoretical maximum. If the factory has unmet demand, determine whether the engines lack steam, are disconnected, or have reached their available capacity. Those cases require different fixes.