This screenshot shows a heads-up display provided for monitoring the status of a character’s power armor in the power armor overhaul mod Powered Power Armor, released for Fallout 3 and Fallout: New Vegas on the Nexus Mods website.
The Vault Tec boy in power armor icon (recycled from existing game assets) indicates armor charge by cycling from green (fully charged) to red (nearly discharged) to grey (dead battery) as the user operates their armor. The exact amount of power remaining is shown in kilowatt-hours to the right of the icon. In the case of atomically powered armors, the kilowatt-hour readout is replaced by a radiation symbol (see video below.)
The two temperature displays above and below the power level readout indicate the armor's operating temperature, changing from green to red as the hydraulically powered arms or legs overheat due to excessive inventory weight, melee combat, sustained sprinting or recoil reduction, etc.
The flame symbol indicates the currently equipped armor-integrated defense system, in this case a pyrotechnic discharge, with color and transparency conveying the charge status.
Night vision power armor helmet upgrade.
Retextured laser rifle that integrates with power armor (draws on common power supply for ammunition)
This video shows the power armor initialization sequence that plays when a user equips power armor (Fallout: New Vegas version only.) The icons that cycle during calibration, drawn by Bethesda forum member The 3rd Type, indicate which of the user's available armor upgrades are compatible with their currently equipped power armor, in this case the Energy Pulse Generator armor defense system, Neural Targeting Interface ranged weapon targeting assist, Proximity Alert combat scanner, and StimJak stimpak delivery system.
