# How do you get energy from matter with 100% efficiency?

Using $$E=mc^2$$, how can you make some energy from matter 100% efficiently? For example, if I gave you about 1 kg of mass you could get a whopping (9*10^16) joules of energy with 100% efficiency. The problem is how do I get the perfect 100% efficiency? Do I use positrons? Do I use antimatter annihilation?

So just to clarify how do I get 100% efficiency? That is the summary of the question. Can you please answer this question for me? It will help me by 1000%. Thank you for reading this and can you please comment on this? If you answer that will be exlemporary!

• This is too vague to answer. You should include more detail. Commented Nov 15, 2022 at 7:48
• Electron-positron annihilation Commented Nov 15, 2022 at 7:49
• You might have more luck asking this on engineering.SE. The question is about extracting energy with the highest efficiency. Commented Nov 15, 2022 at 8:08
• @josephh vague, how? the question could not be any clearer IMO. In any case Ghoster has answered it. Commented Nov 15, 2022 at 9:52
• @m4r35n357 The original question was just “using e=mc2 how can you make some energy from matter 100% efficient please tell me!” That’s it. My comment applied to that version of the question. Since then the OP took the advice to include more detail, and has substantially edited the question to include more detail, so my original comment may not be as relevant to this latest version. Thanks Commented Nov 15, 2022 at 19:17

It depends what you mean by 100% efficiency. If 0.5kg of matter is anhilated by another 0.5kg of antimatter, then you would have released $$9*10^{16}$$ joules of energy into the universe. However, if you want to harvest 100% of this energy to do useful work, then you are out of luck because of the laws of thermodynamics. In layman's terms, whenever any energy changes form, some energy must be lost to useless heat. This principle is true for any kind of energy source, be it solar power, wind power, etc.