Systems and methods for treating a subsurface formation are described herein. A system for treating a subsurface formation may include a plurality of wellbores in the formation. The system may include at least one heater positioned in at least two of the wellbores. The system may include a self-regulating nuclear reactor. The self-regulating nuclear reactor may function to provide energy to at least one of the heaters to raise the temperature of the formation to temperatures that allow for hydrocarbon production from the formation. A heat input to at least a portion of the formation over time may approximately correlate to a rate of decay of the self-regulating nuclear reactor. A spacing between at least a portion of the plurality of wellbores in the formation may correlate to a rate of decay of the self-regulating nuclear reactor. The self-regulating nuclear reactor may decay at a rate of about 1/E.