The V-Capacitor is one of the most important V-Buildings as it helps prevent the most common danger of using the V-Grid, brownouts and deficit stalling. The additional energy storage is exceptionally useful for the V-Grid and Rift Lab energy production stability.
During brownouts, the V-Reactor can stall²⁾ which can complicate the energy and V-Grid management though this is actually only a bit more than a nuisance. The additional buffer of energy storage provided by V-Capacitors prevents far more dangerous and disasterous problems typically caused by instances like mass-Bomber squad landings, sudden Sniper barrages, and sudden Mortar volleys/activity which can suddenly drain all stored energy and create a deficit-feedback-loop. When at a deficit, units stop getting the maintenance energy they request and in response, begin to increase their demand which was originally satisfied by the energy packets sent upon request which didn't need to arrive, only be sent. This immediate satisfaction caused the demand of individual units to be short-lived and small, essentially being an energy tax of say, 1 every 10 seconds as opposed to a recharge which would have 2 per second or 20x the demand. Now however, the demand is constant and when just before you had a stable energy flow from only maintaining units, because you had 0 energy for more than a moment, you are now deep within 40+ deficit as more and more units now demand energy for recharging rather than for ammo maintenance and on top of that, the V-Reactors can stall and make it even worse at unpredictable times and frequencies. \\This is a massive danger especially and hazardously caused by units with a high demand rate for energy. The more energy a unit can demand in less time, the more it can demand when trying to recharge. This is why my (Vertu) units like the Fighter and Blaster cause a deficit of over 40 from having only one Fighter or Blaster requesting ammo when energy storage is at 0. This is also why reducing the request rate of ammo for Fighter(s) can cause a 40+ deficit to turn into a 0 deficit instantly. When a squad of Fighters comes to restock during any deficit, they worsen then deficit by adding over 40 to it. Telling them to only request energy at a default rate (2 per second) in response however, typically instantaneously solves the deficit or brings it back to reasonable levels and once you tell them to request energy back at their maximum rate when no longer in a deficit and with no change in energy generation, you can typically sustain their energy demand because they didn't begin requesting significant amounts of ammo when you where at any deficit. This phenomenon can quickly cause deficits of over 100 which is enough to cause Nullifiers to no longer sustain operation once there are multiple of these high-demanding units requesting recharge during a deficit. The V-Capacitor becomes ever more important from this phenomenon as with high-demanding units, entering into any deficit increases energy demand which creates more deficit which increases energy demand which creates more deficit and so on until every unit is requesting a recharge at their maximum rate of demand.

Units which can request 30 energy a second don't request 30 energy a second unless they are lacking 30 ammo which have not already been sent. So more realistically if we stick to our time in seconds and not frames, when lacking 60 ammo.
The only time this unit is missing 60 ammo is when the ammo maintenance of the unit is not met because a deficit is in effect, when it completed building, or a script altered it's current ammo directly.
V-Capacitors prevent the most common and deadly version of this which is when a deficit is in effect because when something suddenly needs energy for recharging rather than maintenance, there is more stored energy to provide for this temporary increase of demand while still keeping all other units happy and energy demand from them low. Without this additional buffer, 100 energy is nothing when there are high-demand units in action and even still, is very small in vanilla CW4. The moment a deficit occurs for what ever reason, all units using energy can no longer be given the energy from their maintenance demand as energy use is greater than energy generation at this moment in some way along with the lack of stored energy. There is no longer enough available energy to distribute to all sources of demand at this very moment. In cause of this, some units no longer have 1 unit of ammo in need of refilling as maintenance, they now have 2 as energy has yet to be sent to them because there is no longer enough energy to distribute to all sources at their demand simultaneously. With the unit's maintenance demand unmet, the units now demand more maintenance energy up until their maximum/assigned request rate which would then mean they request energy for recharging and not maintenance.
This quickly spirals out of control and can be very difficult to resolve as ideally, you would want to have an energy use equal to energy generation, meaning no energy is being wasted (going to energy storage rather than being used is also a case of not wasting energy, yet another bonus from using V-Capacitors) but since units request less energy after recharging and instead request energy for maintenance, you are no longer using available energy efficiently (since it just lowered) and so build more units to use more energy as their maintenance while in action. So on and so on until a neat balance is reached where the normal activity of all active units causes a maintenance demand of energy very similar to the amount of energy being generated while not being greater than. But as said before, the moment a deficit occurs, this balance is ruined and every unit now demands energy at their maximum rate rather than for maintenance and a 40-100+ deficit occurs instantly. V-Capacitors make it harder for a sudden increase in energy demand to cause a deficit and create this death-spiral of energy demand.