Energy, health, or life is the power that the Power Suit uses for its functions. Samus Aran needs energy for her Power Suit to function properly and for her to survive. If Samus were to run completely out of energy, she would die. Upon taking damage from enemies or environments, Samus's energy is drained. Samus can replenish energy, however, by finding Energy Balls, Phazon Units, Anti-Phazon Units, or various other forms of health regeneration. If Samus's Energy Tanks are full, she can still obtain energy units, but they will not have any effect whatsoever. She can increase how many Energy Tanks she can hold by finding the Energy Tank expansions.