The famous Bitcoin expert Andreas Antonopoulos has published on Twitter a sort of mini-guide on how to avoid high commissions on BTC transactions.
In fact, as Antonopoulos points out, during periods of euphoria the capacity of the Bitcoin network is put to the test, resulting in congestion and slow and expensive transactions.
The first step he suggests to do is to control the level of network congestion.
In fact when a BTC on-chain transactions are sent, this does not end immediately in the blockchain, but in the so-called Mempool.
The Mempool is nothing more than the list of transactions in the queue, waiting to be placed in a blockchain and confirmed.
The suggested tool is the graph called „Johoe’s Bitcoin Mempool Size Statistics“, which shows minute by minute not only the amount of transactions in the queue, but also breaks them down by fee range, expressed in sat/B (ie Satoshi per Byte).
It must be kept in mind that, in general, in each block there are about 2,500 transactions, so it is sufficient that there are less than this figure in addition to a certain level of fee to be almost certain that, falling within that level of fee, it is possible to have a transaction confirmed already in the next block.
Don’t forget that usually a new block is undermined every about 10 minutes, so for example, if it takes three blocks before a transaction is confirmed, you will need to wait about 30 minutes.
How to check fees on Bitcoin: Andreas Antonopoulos‘ Tips
In addition, miners, of course, choose to include transactions with higher fees in the blocks, since they collect them, so inevitably transactions with higher fees are more likely to be included in one block before the others.
Antonopoulos remembers that different types of transactions have different sizes in Bytes, depending on the complexity, the number of input/output and the type of address spent, but that generally a typical transaction with one input and two outputs has a weight of about 144 B.
In reality some wallets do not allow you to set the fees as you like, so in those cases the only thing to do is to wait for a moment of low congestion.
In addition, in case of wallets that allow you to set them, the „legacy“ addresses starting with „1“ are those that require heavier, and therefore expensive transactions, while those Segwit starting with „3“, or native Segwit starting with „bc1“ are the best.
Even better to use wallets that support the „bumping“ of commissions, i.e. the possibility to try with a low rate, and then eventually increase it in case of excessive slowness.
In case of too low commissions the transaction might not be confirmed, but in that case BTCs would not be lost: they would simply go back to the sender, and the transaction would be cancelled. If the network is congested for a long time, it may take up to 14 days before the transaction is cancelled and the BTCs go back, but usually 2 or 3 days are enough.
However, as long as a transaction is pending, BTCs sent with that transaction are effectively blocked.
So it is important to choose a wallet that allows you to have Segwit addresses, set fees as you like, and change them while the transaction is still pending.