Alex_brunius wrote:
In my current game I have 50 core provinces for each 1 province producing oil, and they all cost 5000 oil to fully upgrade infrastructure on.
Alex there is no need to build infrastructure on non-productive provinces. Infrastructure only increases production in that province where it is constructed. So if you have one oil province, a couple of metal provinces, a couple of food provinces and a rare materials province that should be 6 provinces that you need to invest L3 infrastructure in to maximize production. Now Infrastructure does have other uses, such as higher speed roads for units and morale, but that doesn't factor into payback. You may want a nice shiny railroad on every province, but it does not pay the bills.
So lets deal with One oil province.
Base rate of production lets say 3000 tons of oil per day.
A level 1 infrastructure costs you 1000 tons of oil, and takes a day to build. That increases production to +10%
So on day two you make 3,300 tons of oil. If you stop building here you are going to "pay" for the 1,000 tons of oil used to construct the infrastructure in 3.3 days.
If on day two you start a Level 2 infrastructure, that takes 2 days. Another 2,000 tons of oil used for that. So far you have spent 3,000 tons and produced 6,300 tons.
Day three you produce your 3,300 tons of oil.
Day 4 your L2 infrastructure boost oil production to +30%. So 3,900 tons of oil produced.
So at this point on day 4 you have invested 3,000 tons of oil into your infrastructure. Without the infrastructure your oil wells would have produced 12,000 tons of oil. With the infrastructure your wells have made 13,500 tons of oil. Complete payback if you stopped with L2 infrastructure would be in the middle of day 6.
If you continued to make a L3 infrastructure as soon as the L2 was finished it would cost you another 2,000 tons of oil and take 2 days. That would increase production to +50%
Day 5 production is 3,900 tons
Day 6 production is 4,500 tons.
Day 7 production is 4,500 tons. You have achieved payback on the oil production. Without improvement oil production would have held steady at 3,000 per day, making 21,000 tons in total by day 7. The improvements consumed 5,000 tons of oil. With the infrastructure upgrades the oil wells have produced 26,400 tons. So at the end of day 7 you have 400 tons of oil to stick in your pocket, and the following days you have 1,500 tons more each day than you would have had.
So even with the argument that you have to upgrade other resource provinces too, it does pay off. Lets say that you have to build up 5 other provinces at the same time. That will take 25,000 oil. Divide 25,000 by the 1,500 more you are producing each day and it will take just over 16 days to produce. So by day 23 you can start swimming in oil. I know that seems like forever, but it seems to me that day 20 signals the start of heavier action and needing to replace units lost in combat. Might as well have the resources to rebuild the army when needed.