nettoenergiegain

Nettoenergiegain, or net energy gain, refers to the surplus energy produced by a system after accounting for energy inputs and losses. It can be expressed as the difference E_out − E_in in energy units or, sometimes, as a gain factor G = E_out / E_in. A positive net energy gain means the system delivers more energy than it consumes to operate. The concept is central to evaluating the viability of energy technologies and their long-term sustainability.

In nuclear fusion research, net energy gain means obtaining more energy from fusion reactions than is expended to heat, confine, and sustain the fuel. The goal is breakeven or ignition. Practically, researchers compare the energy delivered by the reactor to the energy put into external power sources, such as lasers or magnetic confinement systems. The Lawson criterion describes the plasma conditions required to reach net gain in fusion devices.

In other domains, net energy gain is used to assess solar, wind, chemical, and other energy systems. The calculation accounts for conversion efficiencies, storage losses, and transmission, as well as energy embedded in manufacturing and maintenance. A process might release large amounts of energy per event, but the net gain depends on the total energy invested and recovered over the system’s lifetime. For viability, a positive net gain with a practical margin is typically sought.

The term emphasizes energy quantities rather than monetary cost and should not be confused with profitability or return on investment. It is a measure of how effectively a technology converts input energy into usable output energy.