Factorio steam power ratio: 2 steam engines per boiler
Build 2 steam engines for every boiler, and 20 boilers for every offshore pump: the 1 : 20 : 40 ratio. That block makes 36 MW at full load and burns 9 coal per second.
Where the ratio comes from
| Building | Rate |
|---|---|
| Offshore pump | 1,200 water per second |
| Boiler | Turns 60 water per second into 60 steam per second, using 1.8 MW of fuel |
| Steam engine | Uses 30 steam per second and makes 900 kW |
1,200 ÷ 60 = 20 boilers per pump, and 60 ÷ 30 = 2 engines per boiler. 40 engines × 900 kW = 36 MW.
Fuel
Each boiler burns 1.8 MW. Coal holds 4 MJ, so one boiler uses 0.45 coal per second and a full block of 20 uses 9 coal per second, well within one yellow belt. Solid fuel (12 MJ) lasts three times as long per item.
You do not need the full block at once
Steam engines only use steam when power is drawn, so building the full ratio early wastes nothing but materials. Start with a few boilers and engines in the 1 : 2 ratio and extend the line as demand grows.
Ready-made layouts: power blueprints.