Hearts of Iron IV’s economy is a chain of conversions. Civilian factories build the buildings that become military factories; military factories turn resources into the equipment your divisions need; and your economy and trade laws decide how much of that chain you actually keep each month. For a major power the sequence is forgiving. For a minor trying to hold a region by 1941, the order you build in is most of the plan.
This guide covers the factory types and their output, the civilian-versus-military tradeoff, construction queue priority, and the wiki’s own payback math for deciding when to stop building industry and start building equipment.
What this covers: How civilian factories, military factories, the construction queue and economy laws fit together in Hearts of Iron IV. What changed: Coal now powers factories for extra output, and Paradox has said the resource’s effects were nerfed and are still being adjusted. Who should pick this: Players running a minor or middle power who want a working industry by 1941 rather than a queue of half-finished buildings.
The three factory types
The Production page sorts industry into three producing buildings, and their output figures are the foundation for everything downstream.
- Civilian factories — base output 4 industrial capacity per day, rising to 5 when powered. They build and repair everything in the Construction tab, and they also pay for trade, equipment licenses and intelligence agencies.
- Military factories — base 3.5 per day, 4.5 powered. They make land and air equipment: infantry weapons, artillery, tanks, planes.
- Naval dockyards — base 2 per day, 2.5 powered. They build ships, submarines and convoys, and they are not affected by production efficiency.
| Factory | Base output/day | Powered output/day | Produces |
|---|---|---|---|
| Civilian | 4 | 5 | Construction, repair, trade, licenses |
| Military | 3.5 | 4.5 | Land and air equipment |
| Naval dockyard | 2 | 2.5 | Ships, submarines, convoys |
Civilian output is what construction and economy laws multiply; military output is multiplied by factory output modifiers and by each line’s own production efficiency. The two behave differently enough that treating “a factory” as a single resource is the first mistake a new player makes.
Civilian versus military: the tradeoff in cost and time
A military factory has a base construction cost of 7,200 industrial capacity; a civilian factory costs 10,800. The military building is the cheaper one on purpose. What you pay for with the civilian factory is the ability to build more of everything — including more military factories — later.
The wiki treats a civilian factory as an investment that must earn back its price. Its payback time depends on the local infrastructure modifier, the current construction speed bonus, and how many civilian factories the economy law locks into consumer goods:
Payback Time = 10800 / ( Infrastructure Modifier × 5 × (1 + Construction Speed Bonus) × (1 − Consumer Goods Factories / 100) )
Because consumer goods eat into civilian output, the same factory pays back faster under a wartime economy than under a civilian one. The wiki’s worked table, for a typical state with four of five infrastructure levels, shows the spread:
| Economy Law | Payback, minimum speed (−70%) | Payback, 0% | Payback, maximum speed (+65%) |
|---|---|---|---|
| Undisturbed Isolation | 4444 | 1333 | 1159 |
| Isolation | 3077 | 1231 | 985 |
| Civilian Economy | 2286 | 1143 | 847 |
| Early Mobilization | 1524 | 1067 | 688 |
| Partial Mobilization | 1250 | 1000 | 606 |
| War Economy | 1232 | 942 | 571 |
| Total Mobilization | 1111 | 889 | 539 |
The same page gives the switching rule that turns payback into a decision. The ideal moment to stop building civilian factories and start building military ones, to have the most equipment by a chosen target date, is:
Switch Time = Target Time − (2 / ln(2)) × Payback Time
The wiki’s own example: with a payback time of 800 days and a target of January 1944, the switch should happen in September 1937. A 1941 target moves that switch earlier, and a slow, low-speed economy moves it earlier again — which is exactly the bind a minor power is in when its construction speed bonuses are thin.
Construction queue priority
Construction speed in a state scales with its infrastructure level:
Construction speed × ( 1 + State infrastructure × Max Infrastructure Construction Cost Effect / State Infrastructure Max Level )
With the default maximum effect of 1 and five infrastructure levels, a state at three of five infrastructure gets a 1.6× construction multiplier; a fully built state reaches 2×. That is why the wiki recommends filling one state’s building slots at a time, starting with the states that already have high infrastructure. Spreading identical factories across low-infrastructure provinces wastes the multiplier.
Slots, not factories, are the hard limit. Every state has a category that sets its base number of shared slots, and total slots are capped at 25.
| State category | Base shared slots | Example |
|---|---|---|
| Megalopolis Region | 12 | Greater London Area |
| Metropolismetropolis. The largest tier of a player-grown settlement/node; a major economic and political hub in the world. Region | 10 | New England |
| Dense Urban Region | 8 | Southern Ontario |
| Urban Region | 6 | Svealand |
| Sparse Urban Region | 5 | Nebraska |
| Developed Rural Region | 4 | Sardinia |
| Rural Region | 2 | Madagascar |
| Pastoral Region | 1 | Hejaz |
A minor with a handful of Rural and Pastoral states simply cannot match a major’s factory count, so its construction plan has to spend every slot where the multiplier is highest and the resources are already pooled.
Economy laws matter here too, because they set how many of your civilian factories are locked into consumer goods. That number is computed as a percentage of your total factories — military factories and factories received through trade included, naval dockyards excluded — and rounded down.
| Economy law | Share of factories on consumer goods |
|---|---|
| Civilian Economy | 35% |
| Early Mobilization | 30% |
| Partial Mobilization | 25% |
| War Economy | 20% |
| Total Mobilization | 10% |
Moving up that ladder is one of the largest single swings available to a minor, because it converts consumer-goods factories back into construction capacity. It also brings other costs, so it is a deliberate step rather than a reflex.
Finally, factories are not permanent. A civilian factory can be converted into a military one for a base cost of 4,000, and a military factory back into a civilian one for 9,000. Conversion is a way to repurpose an industrial base that no longer matches the war you are fighting.
What military factories actually deliver
A military factory is only as good as the production line it sits on. Each line has its own efficiency, starting at a base of 10% and climbing toward a cap of 50% before technology. The wiki notes the full climb from 0% to a 100% cap takes at most 500 days, and that adding new factories to a line does not drag down the factories already on it — only the newcomers start at minimum efficiency.
Switching what a line produces costs efficiency, and the size of the loss tracks how similar the new item is:
| Change | Efficiency retained |
|---|---|
| Different variant of the same model | 90% |
| Different model of the same chassis | 70% |
| Direct upgrade or downgrade, same type | 30% |
| Indirect upgrade or downgrade, same type | 20% |
| Any other change | 10% |
That table is the argument for committing to a few equipment families early. The Dispersed Industry research branch raises efficiency retention, which softens exactly these penalties.
Resources are the other brake. A production line that lacks a resource takes an efficiency penalty of −5% per missing unit, per resource type, applied per factory and stacking up to −100% on the lowest-priority lines. The wiki’s own example ends with a line showing an average −50% penalty. Resources cannot be stockpiled, so the practical fix is either to buy more on the market — one civilian factory imports up to 8 units of a resource — or to design cheaper equipment.
The industry technology tree frames the strategic choice. Concentrated industry gives more raw factory output; dispersed industry trades some of it for efficiency retention, a higher efficiency base and resistance to strategic bombing.
| Modifier | Concentrated industry | Dispersed industry |
|---|---|---|
| Factory output | +75% | +50% |
| Dockyard output | +50% | +50% |
| Max factories in a state | +100% | +100% |
| Production efficiency retention | — | +50% |
| Production efficiency base | — | +25% |
| Factory bomb vulnerability | — | −55% |
The wiki’s summary: concentrated industry produces more after roughly a year to a year and a half on the same line, while dispersed industry produces more in the first year or so of a new line, and in the first two to three years of a line switched to an upgraded version of the same equipment.
Ramping a minor into a regional power by 1941
Put the pieces together and the 1936-to-1941 run for a minor power looks like a plan rather than a pile of construction orders.
Start in construction. Pick the two or three states with the highest infrastructure, fill their slots, and let civilian factories build more civilian factories while the payback is still short and the consumer-goods share is still high. Research Construction I and its successors — each gives +10% construction speed and +10% factory repair speed — and watch for the trade laws that add construction speed, since Free Trade gives +15% and Export Focus +10%.
Move your economy law up the ladder when you can absorb it, because every step frees civilian factories from consumer goods. Convert or repurpose once the shape of the war is clear; the 4,000-cost civilian-to-military conversion is the flexible tool, while the 9,000-cost reverse conversion is the expensive one.
Then switch. Use the payback formula against your own target date rather than a streamer’s. When the switch lands, commit military factories to a few equipment families and leave them there, because switching lines later pays the 90/70/30/20/10 retention tax. The equipment those lines produce is what fills the divisions in our HOI4 division template guide, so the two decisions should be made together, not in sequence.
Trade and licenses fill the gaps a minor cannot research alone. One civilian factory can import up to 8 units of a resource, and a production license for 1936-or-earlier technology costs one civilian factory, rising by one for each technology year beyond 1936. Licensed gear carries its own output penalty, so it is a bridge, not a destination.
The newest wrinkle is coal. The wiki lists coal among the seven strategic resources and ties it to powered factory output: civilian factories go from 4 to 5, military from 3.5 to 4.5 and dockyards from 2 to 2.5 when powered. In a Steam dev corner, Paradox said coal was added with the free update released alongside No Compromise, No Surrender, that its effects were nerfed until they “didn’t really matter anymore,” and that further changes are planned. For a 1941 minor, that means treating energy as a soft ceiling on how far a factory count can be pushed before the output stops being worth the slots.
None of this replaces battlefield skill — supply, naval defense and air cover all bite harder against a small economy. Our HOI4 naval and air warfare mechanics guide covers the layer that protects the trade routes feeding this economy. But a minor that plans construction, economy law and the military switch as one timeline reaches 1941 with an industry, not just a wish.
Next read
- For the templates that consume everything your factories produce, see HOI4 Division Templates: Combat Width and Stat Math.
- For the wider division and combat reference, see Hearts of Iron IV — The Division Templates & Combat Reference (Part 2 of the HOI4 Guide).
- For where the 2026 country packs fit around your next campaign, see HOI4 2026 Country Pack: Romania and Focus Trees.
- For the naval and air layers that protect your economy, see Hearts of Iron IV Naval and Air Warfare Mechanics: Task Forces, Missions, and Detection.