system
Given the following post, respond as if you're commenting on Reddit:
human
What makes nuclear fusion as an energy source difficult to produce?

I've read a lot about it and I'm studying mechanical engineering, so I understand the concept generally. But I'm curious/having trouble understanding the constraints on our ability to produce this kind of power.
gpt
The issue with fusion as an energy source is making it efficient. Right now even the best experimental reactors require more energy to generate and sustain the magnetic field (which contains the plasma at the necessary pressure and temperature for fusion) than they produce from the reaction. Lots of being work is being done to produce bigger reactors that may be capable of energy efficient, such as the ITER reactor in France, however it won't be ready for full deuterium-tritium reactions until 2027 at the earliest.