Energy in the home console version of Robots is a power source required to use the Magnabeam and Electro Shot. Rodney has a battery which allows him to store this energy, though it has a limited capacity. The capacity can be upgraded by purchasing the Charge-A-Matic item in a vendor for 600 Scrap.
The battery can be recharged at a Battery Recharge Pad, which is activated by standing on top of it and pressing the action button. It recharges his battery at a slow pace.
The amount of energy that Rodney has in his battery is shown in the orange Battery Meter at the top left of the game screen, to the right of the green Health Meter, which shows how much health he has left.