Understanding Gas and EIP-1559

Hello! Welcome back to our course.

In the last lesson, we traced the entire lifecycle of a transaction, from its creation and signing to its final inclusion in the blockchain. We noted that a transaction's journey is powered by an economic incentive—the transaction fee—but we deferred the details. Today, we'll dive into that crucial topic.

The fee you pay for a transaction isn't arbitrary. It's determined by a sophisticated market mechanism designed to balance network security, usability, and economic sustainability. Understanding this is fundamental to building efficient and cost-effective applications on Ethereum.

Learning Outcome: By the end of this lesson, you will be able to analyze the factors determining transaction cost (gas) and the fee market mechanism (EIP-1559).

1. The Fundamentals of Gas

Before we can understand the market, we need to understand the product being sold: gas.

In the EVM, every single operation—from adding two numbers to writing data into storage—has a fixed cost. This cost isn't measured in ETH, but in a separate unit called gas. Gas is a measure of computational effort. A simple operation like ADD costs very little gas, while a complex one like creating a new contract or SSTORE (writing to storage) costs a lot.

The total fee you pay for a transaction is then calculated as:

$$\text{Transaction Fee}=\text{Gas Used}\times \text{Gas Price}$$

• Gas Used: The sum of the gas costs of all operations executed in your transaction.
• Gas Price: The price you pay per unit of gas, denominated in ETH (usually in a smaller unit called Gwei, where 1 Gwei = $10^{-9}$ ETH).

This separation of computational cost (gas) from monetary cost (ETH) is a key design choice. It allows the price of computation to float with network demand, independent of ETH's market price.

To get a clear overview of these core concepts, let's start with a short video.

As the video explains, when you send a transaction, you also set a gasLimit. This is the maximum amount of gas you are willing to let your transaction consume. It acts as a safety valve. If your transaction runs out of gas before completing, the EVM reverts all state changes but still consumes the gas used up to that point, and you pay the fee for the work done. If it completes using less gas than the limit, the unused gas is never charged.

2. The Old World: The First-Price Auction Problem

Prior to the London Hard Fork in August 2021, Ethereum's fee market operated on a simple first-price auction model. Users would specify a single gasPrice they were willing to pay. Validators (then miners) would look at the pool of pending transactions (the mempool) and prioritize those offering the highest gasPrice, as they kept 100% of the fee.

This led to several problems:

• Fee Volatility: During periods of high demand (e.g., an NFT mint), users would get into bidding wars, causing gas prices to spike unpredictably.
• Poor User Experience: It was difficult for wallets to estimate the "correct" gas price. Users had to choose between overpaying to get in quickly or risking a long wait time by bidding too low.
• Inefficiency: Because it was a blind auction, many users ended up paying far more than the minimum price that would have secured their spot in the block.

To truly grasp these inefficiencies, it's helpful to think about the value validators were extracting. The following video provides a deep and insightful analysis of the pre-EIP-1559 market dynamics.

As you saw, the old system was not only inefficient for users but also created complex incentives for miners. The goal of a new system was to reduce the "auction MEV" (user overpayment) and do something more productive with the "base MEV" (the congestion fee).

3. EIP-1559: A Modern Fee Market

EIP-1559 completely redesigned the fee market to address the problems of the first-price auction. It introduced a new transaction type (0x02) and a new set of rules.

The core idea is to separate the transaction fee into two parts: a base fee and a priority fee (tip).

3.1. Base Fee and Priority Fee

• Base Fee (baseFeePerGas): This is a protocol-defined fee that is burned (destroyed), removing it from the ETH supply. It is the minimum price per unit of gas required for a transaction to be included in a block. Crucially, this fee is not set by the user but is calculated by the network for each block.
• Priority Fee (maxPriorityFeePerGas): This is an optional "tip" that the user includes in their transaction. This fee goes directly to the validator as an incentive to prioritize their transaction over others.

The total price per gas a user pays is baseFeePerGas + priorityFeePerGas.

3.2. Dynamic Block Size and Base Fee Adjustment

The real innovation of EIP-1559 is how the baseFee is determined. The mechanism aims to keep blocks, on average, 50% full. Ethereum blocks have a gasLimit of 30 million gas, but the EIP-1559 mechanism targets a size of 15 million gas.

The baseFee for the next block is adjusted based on the size of the current block:

• If the previous block was exactly 50% full (15M gas), the baseFee remains the same.
• If the previous block was more than 50% full, the baseFee increases for the next block. The network is congested, so the price to get in goes up.
• If the previous block was less than 50% full, the baseFee decreases. The network has spare capacity, so the price to get in goes down.

This creates a predictable, automated pricing mechanism. The baseFee can increase or decrease by a maximum of 12.5% per block, which smooths out volatility and makes fees much easier for wallets to estimate.

Given your background in radiophysics, you might find the underlying mechanics of this adjustment familiar. It is a classic example of a proportional controller, similar to how a thermostat regulates room temperature.

3.3. The Developer's Perspective

As a developer, you interact with this system through the transaction object. Instead of a single gasPrice, you now specify two values:

• maxFeePerGas: The absolute maximum total fee (base + priority) you are willing to pay per unit of gas. Your transaction will fail if the block's baseFee exceeds this value.
• maxPriorityFeePerGas: The maximum tip you are willing to pay the validator.

The actual tip paid will be min(maxPriorityFeePerGas, maxFeePerGas - baseFee). This ensures you never pay a tip that would push your total fee over your specified maxFeePerGas.

So, how do you determine what values to set? You can query a node for the fee history.

3.4. Economic Implications: The ETH Burn

A major consequence of EIP-1559 is that the baseFee is burned, permanently removing that ETH from circulation. This ties network usage directly to the scarcity of ETH. During periods of high network activity, more ETH is burned. This can, at times, lead to the total ETH burned being greater than the ETH issued as rewards to validators, making ETH a deflationary asset.

Conclusion

We've covered a lot of ground, moving from the basic concept of gas to the sophisticated mechanics of the EIP-1559 fee market. This mechanism is a cornerstone of modern Ethereum, balancing the needs of users, developers, and validators.

Key Takeaways:

• Gas is the unit of computational work, while the transaction fee is the monetary cost paid in ETH.
• The pre-EIP-1559 first-price auction was inefficient and led to a poor user experience with volatile, unpredictable fees.
• EIP-1559 introduced a base fee (burned) and a priority fee (tip for the validator).
• The baseFee automatically adjusts based on block fullness, creating a more stable and predictable fee environment. This adjustment mechanism acts like a proportional controller.
• As a developer, you now submit transactions with maxFeePerGas and maxPriorityFeePerGas to navigate this market.
• The burning of the base fee introduces a deflationary pressure on ETH, linking network activity to its economic value.

In our next lesson, we will shift our focus from the network's mechanics to its participants. We will explore the two fundamental types of accounts on Ethereum: Externally Owned Accounts (EOAs) and Smart Contract Accounts, and analyze what makes them distinct.