Production

Production refers to the manufacturing of equipment such as tanks, guns, planes and ships used by the military to conduct a country's war. The construction of buildings in states and provinces, including both military installations and economic development, is known as construction.

Factories

There are three types of factories:

• Civilian factories: Construction (including repair), trade, and consumer goods.
• Military factories: Infantry equipment, transport, artillery, armor, and aircraft. These have a base output of  5. This value is then multiplied by Production Efficiency.
  Thus, the production formula is : ${\text{Production}}=({\text{Base Output}}\cdot {\text{Output Modifier}})\cdot {\text{Production Efficiency}}$
  For example, at 50% Production Efficiency with a 10% Modifier on Factory Output, the production would be $({5}\cdot {1.10})\cdot {0.50}={2.75}$
• Naval Dockyards: Ships, Submarines and Convoys. Have a base output of  2.5, but always have a production efficiency of 100%. Output do effect.

The main output modifiers for military factories and naval dockyards are Concentrated or Dispersed industry technology, while civilian factories are mainly affected by Construction industry technology and the economy law.

Production lines

See also: Construction
for production by civilian factories

Production of military and naval factories/dockyards are organized into production lines, each of which produces a single type of equipment at a time. Up to 150 factories may be assigned to a single production line, but a country can operate lines producing the same item. Ships have a lower limit of dockyards that can be assigned to build them. Capital ships may, at any given time, have no more than 5; screen ships, 10; submarines and convoys, 15.

Production Efficiency

Loss in production with respect to the fraction of starting production efficiency versus the production efficiency cap. This is measured in factory-days relative to running at production efficiency cap for the entire period.

Each production line has its own efficiency level which determines how good it is at producing its current equipment. The higher the efficiency, the faster the production line produces equipment, up to a maximum value. Running the same production line continuously gradually increases its efficiency.

Production efficiency starts at a base (10% without modifiers) and increases each day up to a production efficiency cap (50% without modifiers). All of these can potentially be increased by industry technology, research, and national focuses. The base production efficiency growth per day is:

${\text{Production Efficiency Growth per day}}=0.001{\frac {\left({\text{Production Efficiency Cap}}\right)^{2}}{\text{current Production Efficiency}}}$

(All quantities can be expressed in terms of percent or as a fraction, as long as they are expressed in the same terms everywhere.)

The minimum possible base growth per day is thus about 0.05% (near the starting cap of 50%), and the maximum 1% (10%/100% production efficiency).

Alternatively, the relative time in days to reach a particular level of production efficiency is given by

$t=500\left({\frac {\text{Production Efficiency}}{\text{Production Efficiency Cap}}}\right)^{2}$

For example, going from 25% of the cap to 75% of the cap takes $500\cdot 0.75^{2}-500\cdot 0.25^{2}=250$ days.

Therefore it takes at most 500 days for a fully-supplied line to reach the cap. This represents a shortfall of at most 166.6 factory-days of output relative to a factory running at cap for the same period.

Production efficiency is tracked separately for each factory. Adding one or more new factories to an existing production line reduces production efficiency of the added factories. It is important to know that the factories already in the line do not lose efficiency - what they are making has not changed. Only the new factory has minimum efficiency.

Caution: When military factories are lost or damaged and total factory count declines, the loss comes off the bottom of the list and those factories lose their efficiency. A wise precaution is to move your high priority and high efficiency production lines up in the list.

Production Efficiency Retention

Also, switching a production line to a related type of equipment cancels production of the current unit and the time spent on it, and reduces its efficiency depending on how drastic the change is. However, the player gets to keep a % of efficiency based on the change type. See below.

• 90%: Different variant of the same model (e.g. Panzer III Ausf. F -> Panzer III Ausf. G [variants of the German medium tank 1])
• 70%: Different model of the same chassis or airframe (e.g. Panzer III -> StuG III [German medium tank 1 to medium tank destroyer 1])
• 30%: Direct upgrade of the equipment of the same type (e.g. Panzer III -> Panzer IV [German medium tank 1 to medium tank 2])
• 10%: Any other change (e.g. Infantry Equipment 1 to Towed Artillery 1)

Except for changing of variant which is always a loss of 10%, these effects can be reduced by researching

• Dispersed Industry I to IV
• Flexible Line (the 1943 technology in the Machine Tools tree)

Each of those tech provide a production efficiency retention bonus, which serves to limit the production efficiency loss when switching production lines.

Calculating Production Efficiency with Retention bonus

When a production line is switched while having Dispersed Industry unlocked and/or Flexible Line unlocked, the new Production Efficiency is not the result of a simple addition of the base efficiency (listed in red in the previous section) and the Production Efficiency Retention bonus obtained from the technologies. The exact calculation is more complicated than that, partly due to the fact that if the bonus was simply added, we would achieve a Production Efficiency higher than 100%. Of if it was capped at 100%, high level Retention would become useless in some cases.

The new Production Efficiency can be calculated in three steps. First, the current Production Efficiency (not the cap) is multiplied by the Base Efficiency detailed above (ie. 90% when switching variants, 70% for same chassis or airframe, etc.). Second, the Production Efficiency lost is multiplied by Production Efficiency Retention. The remaining Production Efficiency lost means the difference between the initial Production Efficiency and the result obtained in the first step. For example, with a Production Efficiency of 80% and switching production from Panzer III to StuG III, the Production Efficiency lost is 80% - (80% * 30%) which equals 56%, multiply this value (56%) by the Production Efficiency Retention currently researched and this is the result of the second step. Finally, add the result from the first and second step to obtain the new Production Efficiency.

Note that a base production efficiency superior to this result will supersede it.

It is possible to express these three steps into one formula that will compute the new production efficiency:

${\text{Production Efficiency with Retention}}=CPE*\left({\text{RET}}+\left(1-{\text{RET}}\right)*{\text{BON}}\right)$

Where

• CPE: Current Production Efficiency;
• RET: Retention (the values in red above, or 10% for any other production switch);
• BON: Efficiency retention bonus obtained through Dispersed Industry I to V or Flexible Line.

With this formula we can see that bonus (BON) is more effective with high retention (RET)

To summarize, the real production efficiency will be given by ${\text{Real Production Efficiency}}=MAX\left({\text{Production Efficiency with Retention, Base Production Efficiency}}\right)$

Ships, submarines and convoys are produced in dockyards, which do not have production efficiency but are still affected by output tech. Instead, every dockyard produces a flat 2.5 per day, plus any output boost. Although all progress (and so time) on an incomplete ship is lost if the line changes to another ship, the dockyard will function at 100% efficiency as it starts work on a selected alternative ship design.

Resources

Each nation can use a percentage of the resources on its territory for military production. This percentage depends on the trade law, with Closed Economy giving 100%.

The total amount of resources can be increased by researching the Excavation technologies (under the tab 'industry'). Each level of Excavation technology gives a resource gain efficiency increase of +10% to the total of all extracted resources (extracted resources are those that come from the ground via drilling or mining or that are produced via a Synthetic Refinery; it does not include resources from trade). There are five (5) levels of Excavation technology; researching all of them will give a +50% bonus to the extracted resources total.

The total amount of resources can also be increased by building infrastructure. Each level of infrastructure gives a resource increase to the total of all extracted resources (except those resources produced by a Synthetic Refinery or resources acquired via trade) in a state. The increase varies with both the starting quantity of resources and starting level of infrastructure. This is shown in the example table below for the resource Steel.

Tag	State	Infrastructure Level	Total Steel	Steel Increase
GER	Moselland	7	100	0
GER	Moselland	8	106	+6
GER	Moselland	9	112	+12
GER	Moselland	10	118	+18
GER	Sachsen	7	90	0
GER	Sachsen	8	95	+5
GER	Sachsen	9	101	+11
GER	Sachsen	10	106	+16
USA	Tennessee	5	90	0
USA	Tennessee	6	96	+6
USA	Tennessee	7	102	+12
USA	Tennessee	8	108	+18
USA	Tennessee	9	114	+24
USA	Tennessee	10	120	+30

Resources cannot be stockpiled—they flow directly to production with any excess resources being effectively wasted.

Different kinds of equipment require different resources to produce. Lacking sufficient resources will apply an increasing efficiency penalty up to -100% to the lowest priority production lines. The penalty increases by -5% per missing unit of resource per type and the highest applicable penalty is applied to individual factories. For example, when having 2 units of steel and 0 units of aluminum available and adding a new production line for Support Equipment (needs 2 steel, 1 aluminum) with 11 factories, the first factory receives a penalty of -5% because it misses one unit of aluminum. The second factory receives -10% penalty because it both misses two units of steel and the second unit of aluminum. For each of the remaining factories the penalty increases by -10% because they need two additional steel, the last one getting a -100% penalty. The production line shows the average penalty across all factories, -50%. This penalty stacks multiplicatively with other modifiers.

There are six strategic resources:

Icon	Resource	Description	Equipment
	Oil	Oil is important for making any form of vehicle run.	Not used in manufacturing, but instead refined into fuel, which is used by ships, aircraft and ground vehicles to operate.
	Aluminum	Aluminum is important for the construction of specialized vehicles and aircraft.	Aircraft Support Equipment
	Rubber	Rubber is important for the construction of most vehicles.	Aircraft Motorized/Mechanized
	Tungsten	Tungsten is a rare hard metal mainly used for anti-tank munitions, but also machine tools and specialized parts.	Artillery and Anti-Tank Medium Tanks Light and Medium SP Artillery and Tank Destroyers Medium SP Anti-Air Jet aircraft
	Steel	Steel is the primary metal for most types of military machinery, whether it be tanks or ships.	Infantry Weapons and Support Equipment Artillery, Anti-Air and Anti-Tank Ships Tanks and Motorized/Mechanized
	Chromium	Chromium is a metal used for the construction of advanced engines.	Heavy, Super-Heavy and Modern Tanks and all variants Large ships (Carrier, Battleship, Super-Heavy Battleship, and Battlecruiser) Level IV small ships (Destroyer, Light Cruiser, Heavy Cruiser, Submarine)

Acquiring resources

There are several ways to acquire more resources:

• Trade for resources.
• Take resource prospecting decisions or certain national focuses.
• Construct Infrastructure in resource-producing states.
• Construct Synthetic Refineries.
• Change Trade Law to keep more domestic production.
• Research Extraction technology.
• Conquer states containing resources.

Equipment

Land divisions and air wings are not produced as atomic units. Instead, factories produce individual tanks, airplanes, and so forth. This equipment is then sent to fill out the country's land divisions and air wings. Unlike resources, equipment can be stockpiled. The stockpiles can be viewed under the Logistics Tab.

Equipment	Supplies
Anti-Air	Anti-air Support Anti-air
Anti-Tank	Anti-tank Support Anti-tank
Artillery	Artillery Support Artillery
Heavy SP Anti-Air	Heavy SP Anti-Air
Heavy SP Artillery	Heavy SP Artillery
Heavy Tank	Heavy tank
H. Tank Destroyer	Heavy Tank Destroyer
Infantry Equipment	Bicycle Battalion Engineers Infantry Marines Mountaineers Paratroopers Military police Recon Cavalry Motorized Mechanized
Light SP Anti-Air	Light SP Anti-Air
Light SP Artillery	Light SP Artillery
Light Tank	Light tank
L. Tank Destroyer	Light Tank Destroyer
Mechanized	Mechanized
Medium SP Anti-Air	Medium SP Anti-Air
Medium SP Artillery	Medium SP Artillery
Medium Tank	Medium tank
M. Tank Destroyer	Medium Tank Destroyer
Modern SP Anti-Air	Modern SP Anti-Air
Modern SP Artillery	Modern SP Artillery
Modern Tank	Modern tank
Modern Tank Destroyer	Modern Tank Destroyer
Motorized	Field hospital Logistics company Motorized Motorized Rocket Artillery Signal company
Motorized Rocket Artillery	Motorized Rocket Artillery
Rocket Artillery	Rocket Artillery Support Rocket Artillery
SH SP Anti-Air	Super Heavy SP Anti-Air
SH SP Artillery	Super Heavy SP Artillery
SH. Tank Destroyer	Super Heavy Tank Destroyer
Super Heavy Tank	Super heavy tank
Support Equipment	Bicycle Battalion Engineers Field hospital Logistics company Maintenance company Military police Recon Signal company

Production licenses

Nations may pay for production licenses from nations that already have researched a technology. The cost is generally 1 civilian factory. Unlike trading for resources, the licensor does not gain the benefit of the civilian factory.

A nation with good relations with a foreign nation can request a license from them to produce the foreign equipment. The equipment type a nation is willing to license out is dependent on their relations. Germany, for example, may not be willing to license out their latest tank or fighter designs, but would be happy to provide Panzer IIs to friendly or neutral nations. National focuses may also provide a way to gain licenses or provide bonuses to license production. Producing licensed equipment will not be quite as efficient as producing the player's own designs. A cutting edge licence production will have a noticeable output penalty, but a design a few years old will be almost as efficient to produce as a self-owned technology. If you aren't in the same faction as the owner of the design, you will also receive a little bit less technical support and manufacturing assistance.

Licensing equipment also gives a research bonus for the related technology if one is interested in unlocking it in the future.

External links

Spreadsheet: [Hearts of Iron IV Resource Distribution by Country]