How to pay for a Tron energy rental in TRX

Short answer

Put TRX on your balance first. The energy order spends that balance. It does not ask you to pay at the moment you rent. One USDT transfer is still a 65,000 or 131,000 order. The top-up is a separate TRX transfer, of the exact amount you were shown, to the address you were shown, within one hour.

There is no card, and "about 25 TRX" does not count

The account holds TRX. You add to it by sending TRX on-chain. You spend it by ordering energy. If the balance is short, the order stops. That is the moment to top up, not after you have already signed the USDT transfer and watched it burn.

The amount has to match, including the awkward cents. A top-up opened for 25 TRX may ask you to send 25.03. Send 25.00 to the right address and it will not credit, because the match is the exact sum, not "close, and we will figure it out." The cents are how two top-ups can be open at once without grabbing each other's payment. It feels fussy until the first collision it prevents.

You can open one from the cabinet or from the API. Five can be waiting. A sixth waits until one of them is credited or expires. There is no bank invoice and no card. The TRX you deposit is the TRX the rental spends, on a price chosen when you order, not on a checkout page.

Why the sum is not always the round number you typed

You ask for a whole number of TRX, at least 1. The amount you are told to send has six decimal places. It is the number you asked for, or that number plus steps of 0.01 TRX, up to 1 TRX more, when each lower sum is already reserved by a top-up that is still open. Send the figure you were given. A different amount is not matched to this one.

You also get an address and a deadline. The window is one hour. While it is open, the top-up is waiting for the transfer. Once the transfer is on the network it still needs 19 confirmations before it is credited. If the hour closes and the transfer had already arrived inside the window, it can still be matched. After it is credited, it drops off the list of unfinished top-ups and shows up as a deposit in the account history. An expired one drops off too. You can still fetch either by its id.

Five unfinished top-ups is the cap. Opening another is refused. If every 0.01 step from your number through 1 TRX above it is already taken, that open is refused as well, and you wait or pick a different whole number. An idempotency key returns the original top-up when you retry the same request. The same key with a different amount is a conflict, so a retry cannot silently change what you owe.

The energy order does not send this transfer again. It debits the balance. There is no price in the order. The debit is the lowest eligible offer, plus activation if the target address was not on the network yet. At the 100-sun snapshot, the burn you are avoiding is 6.428500 TRX for 64,285 energy or 13.028500 TRX for 130,285. The rental debit is the quote for the 65,000 or 131,000 you actually ordered, and the reason to rent is that this quote is under that burn. If the balance is below the debit, nothing is delegated. For an inactive address the balance has to cover the energy and the activation together.

Cancel the energy order later and the energy debit comes back onto the balance. The top-up does not reverse. An activation fee that already created the account does not reverse either. The TRX sits there until a later order spends it. From code, the top-up and the order are both on the energy rental API. The rental itself is the same balance, without the calls.