The Streamline mod increases your warframe's Power Efficiency, which decreases the energy cost of abilities. The cost of activating an ability when using the Streamline mod is:
- Cost = Base Energy Cost divided by (1 + X), where X is the percent power efficiency expressed as a decimal, and the result is rounded up.
Streamline is not a percentage reduction in the energy cost needed to activate an ability, but is instead a percentage increase in energy value. It makes 1 point of energy worth 1.3 at maximum Streamline which effectively reduces the energy cost of abilities.
Below are examples of the base energy cost, and reduced energy cost associated with using a max level Streamline mod, which gives a Power Efficiency of 30%.
|Base Cost||Reduced Cost|
It is important to note, that streamline is not an ability base cost reduction. Thus, a max streamline does not reduce a base cost 100 ability to 70, it reduces it to 76.923 and then rounds up to 77.
If used in conjunction with Essence Loki Helmet, they stack such that:
- Cost = Base Energy Cost divided by [1 + (X+0.15)]
- where X is the percent power efficiency expressed as a decimal
- and +0.15 is Essence's Power Efficiency rating.
Although your energy is displayed in whole numbers, it is not calculated as such. Because of this, using abilities in succession will sometimes result in Power Efficiency causing an ability to cost 1 point more or less energy than its reduced cost would otherwise have been. This is because rounding is only done on your displayed energy, and not on the actual amount of energy remaining.
When using Streamline and activating an ability, the base cost will be shown above your warframe, however your energy will instead be reduced by the reduced cost associated with Streamline.
The example reduced costs associated with base cost 35, and 75 have not been verified in game, and are based only on the formula. If you are capable of verifying either of these two in game, please leave a comment with your findings.
For further reading, and to learn how these numbers were ascertained, check the Power Efficiency page.