Power Units (PU), will give the necessary energy for your miners work nonstop.
Power Units (PU) is the most valuable resource, without them your miners wont work!
To buy Power Units (PU):
Left menu -> City -> Miner Shop -> Buy power
You will be redirect to the shop, just change tab to power units.
Now choose the pack you want, you can buy 1x,2x or 3x packs at once.
Pay attention to the price of the packs, Every pack increases after a set amount of PU you buy.
That means the more PU you have on stock or using the more you will pay per pack.
After you buy the packs, packs will be stored in your inventory.
On the same page press "My inventory" or "Use power"
You will find all your PU available to use.
Tip: Dont buy to many PU or else you will end up paying alot more than you should.
Tip: Houses can only hold a certain amount of PU, make sure you check your limits.