Energizer

"Reduces ability cooldowns everywhere by 20%. While in radius, heroes earn XP 50% faster and water Monkey ability cooldowns are halved."

- In-game description

 is the final upgrade of Path 1 for the Monkey Sub in Bloons TD 6. It makes Heroes earn XP 50% faster while in the radius, reduces ability cooldowns of all nearby water monkeys by 50% (doesn't stack with Bloontonium Reactor), as well as reducing ability cooldowns for ALL other towers on screen by 20%. It also increases the pierce of the Bloontonium Reactor attack from 50 to 1000 and the damage from 1 to 3.

It costs $27,200 on Easy, $32,000 on Medium, $34,560 on Hard, and $38,400 on Impoppable.

Summary
Energizer has the exclusive benefit to grant both additional Hero XP and to grant all abilities on screen with a faster cooldown. Although quite expensive, it is quite effective in combination with slow-leveling heroes, water-based towers and heroes, and ability-dominant defenses. It shines mostly in epic late-game, where much of the main power comes from the various abilities in the player's arsenal, most specifically Grand Saboteur, Homeland Defense, multiple Call To Arms, and Overclocks.

However, outside of custom challenges such as 2MPC, "Axis of Subs", and Level 20 Churchill CHIMPS challenges, its limited niche makes Energizer a less popular option on CHIMPS Mode compared to simply affording additional defense for a similar cost. Energizer is still fairly usable otherwise, and it can greatly enhance the player's defenses if relying heavily on activated abilities, especially water-based abilities.

Tips

 * Just as with its previous upgrade, crosspath with Path 3 to increase its damage output. However, crosspathing 5-0-0 does not really hurt since the tower benefits more from a supporting role in the late game.
 * It is notable that since 18.0, Admiral Brickell's Naval Tactics and Sub Commander can buff Energizer's DPS and this may combo better with the bottom crosspath.
 * This upgrade is very useful when defenses are ability-heavy, particularly with income-related abilities such as Jungle's Bounty, Supply Drop, and Support Chinook's Crate Drop Ability.
 * It is worth noting that the Energizer also affects the life-loss passive abilities of Bomb Blitz, Elite Defender and Legend of the Night.
 * The water heroes Pat Fusty and Admiral Brickell both synergise well with Energizer, as they benefit from both the increased Hero XP and the reduced cooldown on their abilities, especially since their abilities are extremely powerful buffs.
 * Admiral Brickell is arguably the best hero to pair with the Energizer, as her abilities are highly effective for water-based terrain. Similar to Pat, her buff has a much higher uptime.
 * Additionally, with the "Ability Mastery" Monkey Knowledge, it is possible for Brickell in range of an Energizer to provide near-permanent buffs with her Naval Tactics ability.
 * The hero who benefits the most out of the Energizer's bonus Hero XP benefits is Psi. This is because Psi's earlier levels are quite weak, and Energizer's Hero XP buff allows Psi to scale better for the later rounds, where MOAB-class bloons form the majority of the rounds. Captain Churchill is another valuable hero to pair with Energizer because of how slowly he naturally levels up and because of how strong he plays as a pure offense hero. Although Adora levels just as slowly, she has her Blood Sacrifice ability to speed up leveling at a lower cost.

Bugs

 * The visual indicator in the buffs section above a tower inconsistently displays the submerged and unsubmerged buffs. Additionally, sometimes, the bug shows both sprites indicating a submerged and unsubmerged buff. This bug has been known since 12.0 and occurs as of 14.0.
 * When upgraded to 5-2-0, submerged radiation does not increase against leads or DDTs damage unlike previously upgrade.

Sounds
When changing to Submerge target priority: When switching from Submerge to other priorities:
 * [Sonar pulse]
 * [Wave sound]

Trivia

 * The description used to be "Hero earns XP 50% faster while in Energizer's radius. Cooldowns for abilities of water Monkeys in the radius are halved." but has changed due to the changes in Version 2.0.0.
 * The XP boost only works for Heroes in the radius, as verified by Challenge Editor.
 * When crosspathed with upgrades on the bottom path, two guns appear on the bottom of the Energizer.
 * Since Pat Fusty can be placed on water or land, he can benefit from either 50% ability cooldown or 20% depending on where he is placed.
 * Energizer was used to complete the first ever 2 Towers CHIMPS with The Anti-Bloon.
 * The Version 2.0 buff was likely inspired by the High Energy Beacon from BTD5, which grants 20% decreased ability cooldowns for nearby towers, although the Energizer's buff in Version 2.0 affects on a global range.
 * Before the version 10.0 nerf, this used to be very powerful with towers such as Grand Saboteur which has 50% uptime, as it could allow these towers to be active 100% of the time.
 * In Version 23.0, there is a strange interaction where the pierce reworks for Bloontonium Reactor do not equate the same ratio when compared to Energizer, so somehow the Energizer only had an additive +20 pierce and +30 pierce on top for Energizer with Path 2 upgrades.