From Resonant Rise Wiki

Charge is Factorization's form of energy. It is currently produced only by Solar Turbines (prior to Factorization v0.7.15) or Steam Turbines and Reflective Mirrors (After v0.7.15) or by a Caliometric Burner It can be stored in Battery Blocks or Leyden Jars.

Charge is used to power Furnace Heaters, Grinders, and Mixers. It can be measured by the Charge Meter.