Absolute Zero is the final upgrade of path 2 for the Ice Tower. It costs $1700 on Easy, $2000 on Medium, $2160 on Hard and $2400 on Impoppable. Upgrading to Absolute Zero unlocks the Absolute Zero Ability; when used, it will freeze the entire screen of bloons for 4 seconds (including White Bloons and Zebra Bloons). It does not affect any M.O.A.B. Class Bloons, however, Absolute Zero can freeze White Bloons, Zebra Bloons, and Camo Bloons, which the Ice Tower normally cannot. It takes approximately 30 seconds to recharge this ability on Fast Forward.
- This is the only upgrade for the Ice Tower that does not have an animated element to its appearance on the track.
- In some ways and some opinions by experts, this upgrade is the most useless ability of all as it has none damage to bloons at all. However, some people said it can be used to slow down bloon rushes, and it is true. Like in BTD5 Round 63, it can be used to freeze the ceramic rushes and slow down them. Then, we can pop them with hot weapons.
- Absolute Zero is the cheapest of the Special Abilities in Bloons TD 5, by the cost of the final upgrade alone.
- In the mobile versions of Bloons TD 5, Bloons TD Battles and Bloons Monkey City, Absolute Zero will behave like Sabotage Supply Lines against MOAB-Class and Boss Bloons with almost half the cost. This can be combined with Sabotage Supply Lines to reduce the speed of bloons to 25%.
- Absolute Zero, in real life, is the equivalent of 0 K, which means -459.67 °F or -273.15 °C. At this temperature, elementary particles are in a state of complete stasis. Attaining absolute zero is impossible since it would violate the 3rd law of thermodynamics and quantum mechanics. The position-momentum uncertainty principle in quantum mechanics states that the standard deviation in position times the standard deviation in momentum equals the reduced planks constant over 2. A particle at absolute zero would have 0 momentum and a standard deviation of momentum equal to 0. A standard deviation of position multiplied by 0 (the standard deviation of the momentum of a particle at absolute zero) equals zero and not Planck's reduced constant over 2, thereby violating the position-momentum uncertainty principle. Therefore, absolute zero is impossible to attain. Yet another reason quantum mechanics challenges every law of science. (Such as, on an atomic level, an atom can be in two places at once or not exist at all)
- With this information, it is illogical to have some moving frosty air during freezing.
- Also with this information, the Zero Point Energy Machine description mentioning "pure coldness" is not possible in real life.
- It also is illogical that the MOAB-class remain unaffected by extreme coldness, even though all other bloons froze. However, in BTD Battles Mobile, this ability will slow MOAB-class but the Glue Striker ability will not.
- This ability can backfire if you do not have any towers that can pop frozen bloons, so you might need to buy Splodey Darts, or a Bomb Tower to be able to pop the bloons that were frozen.