I think it has potential already, and there are probably several different directions you could take with it. What do you want the focus of the game to be? I think it would be easier to give feedback if your goal as a designer was more clear.
Personally, I like difficult games if they feel rewarding enough. The challenge has to feel fair, so that death is my own fault for not playing it safe enough, and there has to be something that makes me want to get greedy and take risks.
Here I don't see a good way of playing it safe since returning to recharge just means I cover more distance, and there's little (or negative) gain from attempting to gather more gems. It would be different if I'd killed myself after taking a calculated risk, but here I feel like I'm going to die by simply playing without being able to do much to help it. Especially since the cost of recharging increases for each level whereas the gains from mining do not. I end up wanting to avoid any action apart from fetching the astronaut, and then I run out of energy. Making movement (and maybe also mining) less taxing would help a lot to push the balance towards something more sustainable, I think.
It also feels a bit counter-intuitive that failing to move should cost energy, since I'm not technically doing anything (and especially since I'll spend energy when I click on the screen to give the game focus).
Destroying a rock to move past it costs energy, but so does moving past it, making the total energy needed to get past a single rock four units or so, which makes them feel like fairly big obstacles. Having mining drain a single unit of energy would still make rocks twice as costly to traverse as ground.
I think it would feel more like a calculated risk if destroying the rocks occasionally yielded an item that would recharge your vehicle (although I think that actually might have happened once, but it was before I fully understood how the game worked, so I can't say for sure).
I feel like I'm being forced to explore instead of wanting to out of curiosity, or wanting to gather items which could expand the available mechanics or make the game easier (like a laser or something which could destroy more than one rock at a time, for instance). I don't think it's going to take more than a few additions (like different kinds of functional items or new types of obstacles) to give the game some more depth.
Maybe some more on-screen feedback would help, like numbers hovering over the adjacent tiles to show how much energy it'll cost to move there. Or maybe some kind of pathfinding which indicates the fastest path from your vehicle to the tile under the cursor, with an indicator of the energy you'll have to spare when you reach that tile (although that sounds like a lot of work). I think anything that reduces the amount of mental calculation you'll have to do per move would make it feel less tedious.
Looking forward to seeing what you'll do with this.
Bugs:
Sometimes the little astronaut spawned in the top left corner, outside of the level (-1, -1).