New Ethereum Proposal Could Dramatically Cut Gas Fees

Ethereum transactions incur gas fees, which are required to execute operations on the blockchain. One of the significant contributors to high gas costs is storage access, where data is read from or written to Ethereum’s state.

Currently, storage access costs can be inefficient due to how Ethereum treats every transaction separately, even when they are in the same block. A new proposal, Block-Level Warming, aims to optimize how storage is accessed across transactions in the same block, reducing unnecessary gas costs.

This proposal is closely related to Access Lists, which were introduced to optimize storage access but remain underutilized.

In this article, we will learn how storage access works in Ethereum, the inefficiencies in the current system, how Block-Level Warming could improve efficiency, and the challenges that need to be addressed before it can be implemented.

Storage Access Costs in Ethereum

When a transaction interacts with a smart contract, it often needs to read from or write to storage slots. These storage slots hold important data, such as token balances, smart contract states, and historical information.

Ethereum applies different gas fees depending on whether a storage slot is being accessed for the first time in a transaction or if it has already been accessed:

• Cold Access: When a storage slot is accessed for the first time in a transaction, it is considered "cold," and the operation incurs a high gas fee.
• Warm Access: If the same storage slot is accessed again later in the same transaction, the gas cost is significantly lower because it is already "warm."

Currently, every transaction starts fresh, meaning that even if a previous transaction in the same block has already accessed a storage slot, it is still considered cold when accessed by a new transaction. This results in redundant gas costs because multiple transactions are paying high gas fees for the same storage slots in a block.

Let’s say multiple transactions in a block interact with a Uniswap liquidity pool contract to swap tokens. Every transaction accessing the liquidity pool contract has to re-pay the cold access cost to read the same storage slot, even though the same data was accessed just a few transactions earlier.

This inefficiency increases the overall cost of transactions, making Ethereum more expensive to use.

What is Block-Level Warming?

Block-Level Warming is a proposed solution to eliminate redundant cold access costs within the same block.

Instead of resetting storage slots to "cold" at the start of each transaction, Block-Level Warming allows them to remain "warm" for the rest of the block. This means:

1. The first transaction in the block that accesses a storage slot still pays the cold access fee.
2. Any subsequent transactions in the same block that access the same storage slot will only pay the lower warm access fee.
3. At the end of the block, all storage slots reset to "cold" for the next block.

This simple change significantly reduces redundant gas costs, making transactions within the same block more efficient.

The graph shows how block-level warming can reduce Ethereum’s gas consumption by keeping accessed storage slots and addresses “warm” across transactions within a block or multiple blocks.

• The blue line represents the current gas usage, where each transaction pays the full cost to warm storage slots, resulting in higher gas consumption (around 15M gas per block).
• The orange line demonstrates block-level slot warming, where storage slots accessed earlier in the same block remain warm, saving 0.5M–1M gas per block.

By extending the warming period beyond a single block, even greater efficiency gains are observed. The green, red, and purple lines represent warming windows of 5, 10, and 15 blocks, respectively.

• A 5-block warming window (green line) reduces gas consumption by ~1.5M per block (~10% savings).

As the warming period increases, further gas savings are achieved. This analysis suggests that Ethereum could significantly lower transaction costs by adopting block-level warming.

How Block-Level Warming Affects Access Lists?

Ethereum introduced Access Lists to improve efficiency by allowing users to pre-declare which storage slots they plan to access in a transaction. The idea was that by specifying storage access upfront, transactions could be executed more efficiently.

However, Access Lists are underutilized because there are no strong incentives for users to declare their storage slots in advance.

With Block-Level Warming, Access Lists may become less necessary because storage slots accessed in a block remain warm anyway. This means users might not bother including Access Lists, further reducing their adoption.

To address this, Ethereum may need to introduce additional incentives, such as gas refunds or further discounts for using Access Lists efficiently.

Challenges to Block Level Warming

Ethereum clients try to execute transactions in parallel to improve performance. However, if Block-Level Warming introduces dependencies between transactions (since some rely on the storage slots being warm), it could make parallel execution more difficult. Developers need to explore how to balance storage warming with transaction parallelization.

Block-Level Warming could also introduce new attack vectors. Gas griefing attacks involve maliciously warming specific storage slots to manipulate transaction costs. Since warmed slots have lower access fees, attackers can pre-warm irrelevant storage, forcing legitimate users to pay higher gas fees for necessary operations. This tactic can target DeFi protocols or rollups, increasing costs for others while benefiting the attacker, potentially leading to financial inefficiencies or denial-of-service risks.

Block stuffing occurs when attackers flood the network with spam transactions to artificially warm storage slots and alter gas pricing dynamics. By filling blocks with useless warmed slots, attackers reduce their own gas costs while raising costs for others.

This tactic can be exploited in MEV scenarios, where attackers gain an advantage by manipulating execution costs, leading to network congestion and unfair pricing.

Block-Level Warming is a promising gas optimization technique that could significantly reduce redundant cold access fees in Ethereum transactions. However, challenges such as parallel execution, security risks, and the impact on Access Lists must be addressed before implementation.

Further research, testing, and developer collaboration will be crucial to refining this proposal.

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