How to get free energy?

You can use the Rocket Stove. This is unlocked early in the game, keep checking the quests. With the Rocket Stove you can cook some items that you have collected and they will give you more energy. You can also use the campfire. Again, drag your ingredients onto the stove, and once a bar is filled, the campfire will start to produce energy.

Another cool way to get more free energy is to level up! That will restore your energy to full immediately.

Level up for free energy