The healing item that restores energy in Mega Man is the E-Tank, short for Energy Tank. It stores reserve energy that Mega Man can use to refill his health during a difficult stage or boss battle.
The E-Tank first appeared in the original Mega Man, released in 1987. Unlike ordinary health pickups, which restore energy immediately, an E-Tank remains in the inventory until the player activates it. This makes it especially valuable when preparing for a Robot Master or Dr. Wily encounter.
The letter E stands for energy, matching the series’ terminology for both Mega Man’s health and weapon reserves. Later games introduced related items with different functions, including the W-Tank for weapon energy and the S-Tank for a broader refill effect. M-Tank is not the standard healing item in the classic series, making E-Tank the canonical answer.