# Fusion energy, 2MJ input or 200MJ to get 3.5MJ out
**URL:** https://boards.straightdope.com/t/fusion-energy-2mj-input-or-200mj-to-get-3-5mj-out/976492
**Category:** In My Humble Opinion
**Created:** [December 14, 2022, 2:20am UTC](https://boards.straightdope.com/t/fusion-energy-2mj-input-or-200mj-to-get-3-5mj-out/976492 "2022-12-14T02:20:32Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)
#### Post date: [December 14, 2022, 2:20am UTC](https://boards.straightdope.com/t/fusion-energy-2mj-input-or-200mj-to-get-3-5mj-out/976492/1 "2022-12-14T02:20:33Z")
Ive heard that it took 200MJ of energy to create the 2MJ of energy the lasers used to produce the 3.5MJ of output.
Some people said this is an engineering problem, but how exactly is this a net positive fusion generation if the lasers are so inefficient?
Is any of this true, did it still require more energy input than came out of the fusion reaction?
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### Author:  [@Ruken](https://boards.straightdope.com/u/Ruken)
#### Post date: [December 14, 2022, 10:39am UTC](https://boards.straightdope.com/t/fusion-energy-2mj-input-or-200mj-to-get-3-5mj-out/976492/2 "2022-12-14T10:39:53Z")
It depends where you draw the box. Fusion gain is energy out of the fuel over energy into the fuel and doesn’t consider how you got that energy into the fuel.
> [@Wesley\_Clark](#):
>
> net positive fusion generation
No electricity was generated. NIF isn’t set up to generate electricity. And that will have its own losses associated with a typical thermal power plant, requiring even more gain for the overall system to break even.
There’s also a thread in MPSIM.