Transaction Fees

When creating an Avalanche L1 we can configure not only our custom native token, but also how the transaction fees (also known as gas fees) are determined. This allows Avalanche L1s to define the desired or maximal throughput of the blockchain differently.

To adjust the fee dynamics we have the following parameters:

Gas Limit: The total amount of gas that can be used in a single block. This impacts how much computation happens in one block. The value represents the maximum amount of gas a single transaction can use (which would result in a single-transaction block).

Target Block Rate: The target time between blocks, in seconds. This value does not change the base fee. Before the Granite upgrade, it was an input to the block gas cost. Since Granite, it has no effect, but the fee config still requires a value greater than 0. The ACP-226 minimum block delay now limits the block rate. Each validator sets its preferred delay, in milliseconds, with the min-delay-target chain config option.

Min. Base Fee: The lowest base fee, in wei per unit of gas. The base fee of a block cannot go below this value, so every transaction pays at least this price for each unit of gas that it uses. A native token transfer uses 21,000 gas, so it costs at least 21,000 times the minimum base fee.

Target Gas: The targeted amount of gas (including block gas cost) to consume within a rolling 10s window.

Base Fee Change Denominator: The transaction base fee changes with demand of the block space. If the parent block used more gas than its target, the base fee should increase. Otherwise, if the parent block used less gas than its target, the base fee should decrease by the amount. There is a formula behind this that would go beyond the scope of this section, but setting this value to a larger value means that the base fee will change more gradually. Setting it to a smaller value will make the base fee change more rapidly.

Min. Block Gas Cost: The minimum gas cost that a block had to cover before the Granite upgrade. Since Granite, the block gas cost is always 0, so this value has no effect. The fee config still requires it.

Max. Block Gas cost: The maximum gas cost that a block had to cover before the Granite upgrade. Since Granite, this value has no effect. The fee config still requires it.

Block Gas Cost Step: Before the Granite upgrade, this value set how much the block gas cost changed for each second of difference between the time since the parent block and targetBlockRate. Since Granite, the block gas cost is always 0, so this value has no effect. The fee config still requires it.