Energy is a resource in They Are Billions.
Energy is mainly gained from mills, with power plants and advanced mills being alternative options in the late game. It can also be found in batteries on the map.
Almost all buildings require energy. You cannot build new buildings if you don't have the Energy supply for them.
If your colony has negative Energy, attack towers, such as Great Ballistas will begin to shut down.
Note that you don't need Energy supply to repair infected buildings, but they will consume Energy supply after fully repaired, which may lead to negative Energy supply.
| Column 1 ⇅ | [Lightning Spire](/the-lightning-spire) ⇅ | 26 [Mills](/mill) ⇅ | Five [Power Plants](/power-plant) and five average [Sawmills](/sawmill) ⇅ | 13 [Advanced Mills](/advanced-mill) ⇅ |
|---|---|---|---|---|
| Energy provided | 800 | 780 | 780 | 780 |
| Initial cost | 16000 gold, 300 stone, 400 iron, 200 oil (building and research) | 7800 gold, 520 wood | 5500 gold, 250 wood, 150 stone | 10400 gold, 130 iron |
| Minimum footprint | 25 tiles | 104 tiles | 55 tiles | 52 tiles |
| Maximum spaces around buildings | 24 tiles | 312 tiles | 140 tiles | 156 tiles |
| Workers | 60 | 104 | 60 | 52 |
| Maintenance | 100 gold | 156 gold | 220 gold | 520 gold |
Lightning spire is the most space and maintenance efficient source of energy in the game. Power plants are the second most efficient - while they have higher upkeep, they use 2-4 times less space than mills, which can be filled by dwellings and other buildings. Also, power plants require less time to look for placement spots, making them better power source for no-pause runs. Mills have second lowest maintenance, but require much more space and attention, and may hinder productivity of other buildings such as Farms. Advanced mills are the least efficient, having footprint comparable to Power Plant/Sawmill combo and 2.36 times their upkeep.