Gas Fees Configuration

Configuration Format

The fees are configured in the chainConfig in the feeConfig part:

{
  "config": {
    // ...
    "feeConfig": {
      "gasLimit": 15000000,
      "minBaseFee": 25000000000,
      "targetGas": 15000000,
      "baseFeeChangeDenominator": 36,
      "minBlockGasCost": 0,
      "maxBlockGasCost": 1000000,
      "targetBlockRate": 2,
      "blockGasCostStep": 200000
    },
    "allowFeeRecipients": false
  },
  "alloc": {
    // ...
  },
  // ...
    
  "gasLimit": 0xe4e1c0,
  // ...
}

gasLimit

Sets the max amount of gas consumed per block. This restriction puts a cap on the amount of computation that can be done in a single block, which in turn sets a limit on the maximum gas usage allowed for a single transaction. For reference, C-Chain value is set to 15,000,000.

You might be wondering, why is the gasLimit field twice? Well, the reason behind this is that Avalanche introduced it's own fee config under the feeConfig key, while keeping compatibility with the standard EVM config. Make sure to match both fields with the same decimal and hex equivalent value.

targetBlockRate

Sets the target rate of block production in seconds. A target of 2 will target producing a block every 2 seconds. If the network starts producing blocks at a faster rate, it indicates that more blocks than anticipated are being issued to the network, resulting in an increase in base fees. For C-Chain this value is set to 2.

minBaseFee

Sets a lower bound on the EIP-1559 base fee of a block. Since the block's base fee sets the minimum gas price for any transaction included in that block, this effectively sets a minimum gas price for any transaction.

targetGas

Specifies the targeted amount of gas (including block gas cost) to consume within a rolling 10-second window. When the dynamic fee algorithm observes that network activity is above/below the targetGas, it increases/decreases the base fee proportionally to how far above/below the target actual network activity is. If the network starts producing blocks with gas cost higher than this, base fees are increased accordingly.

baseFeeChangeDenominator

Divides the difference between actual and target utilization to determine how much to increase/decrease the base fee. A larger denominator indicates a slower changing, stickier base fee, while a lower denominator allows the base fee to adjust more quickly. For reference, the C-Chain value is set to 36. This value sets the base fee to increase or decrease by a factor of 1/36 of the parent block's base fee.

minBlockGasCost

Sets the minimum amount of gas to charge for the production of a block. This value is set to 0 in C-Chain.

maxBlockGasCost

Sets the maximum amount of gas to charge for the production of a block.

blockGasCostStep

Determines how much to increase/decrease the block gas cost depending on the amount of time elapsed since the previous block. If the block is produced at the target rate, the block gas cost will stay the same as the block gas cost for the parent block. If it is produced faster/slower, the block gas cost will be increased/decreased by the step value for each second faster/slower than the target block rate accordingly.