Elon Musk explains the Kardashev Scale：

"That's the most objective metric that any alien species， say， visiting us would calibrate how much progress we've made as a civilization， and one of the most objective ways to do that is the amount of power that any given civilization has been able to harness， and there was a Russian physicist， actually， who thought about this， and it's， I think， it's a good way to characterize it， which is you can have， you can assess how well a civilization is harnessing the power available on the planet， that's type I. And then type II would be how much of the star's power are you harnessing， and then type III would be how much of the galaxy's power are you harnessing. These are very objective and measurable numbers， so right now we're very low on the Kardashev I scale， like， what proportion of our planet's power are we harnessing， it's a very， very tiny number， and basically we're harnessing almost nothing of our stars' power， so the sun is truly an immense state. We don't even know how to do level III， really. AI will figure it out. One way to appreciate the size of the sun is to think about how heavy is the sun compared to all the rest of the mass in the solar system. So， the sun is about 99.86% of all mass in the solar system. It's everything， and then all the remaining 1.14% most of that is Jupiter， one planet."