The Energy Upgrade Dropdown

The Energy Upgrade Dropdown contains numerous upgrades that can be purchased with energy. Energy will regenerate and you can speed up that regeneration by spending plutonium in the Plutonium Upgrade Dropdown.

There's 2 columns that each represent Raw Materials, and Factories. The energy upgrades apply to all the resources for the given type.

There are also a special upgrades at the bottom, an upgrade to increase the amount of plutonium you earn when watching an ad.