In most cases, Smart Contracts are similar to paper contracts in the analog world. However, instead of ink on paper, they are written as digital text in computer-readable code. The same way a local computer program can be run by selecting it in the operating system, a smart contract can be triggered by calling a method on the contract using a blockchain transaction (TX).
To interact with these contracts, a fee—called gas—must be paid every time a smart contract is about to be executed. Gas is the computational fuel of smart contracts. Each execution of a smart contract consumes gas that must be paid by a user who requests the execution of the code. Execution of a simple smart contract requires very little gas, whereas interaction with a more complex contract requires more.
Gwei is the unit of value used to express the price of gas. Gwei is short for gigawei, or 1,000,000,000 Wei. One wei was first defined as a unit of value on the Ethereum network, equivalent to 10-18 ether (ETH). A wei is the smallest subdivided unit of an ETH, just as a satoshi is the smallest subdivided unit of a bitcoin or a cent is the smallest subdivided unit of a dollar. One gwei is 10-9 ETH, or one ETH is one billion gwei. Because RSK is an EVM (Ethereum virtual machine) compatible chain, gwei is also used as a unit on RSK. However, the base token of RSK is RBTC rather than ETH. Therefore, gwei is defined on RSK as a subdivision of RBTC rather than ETH. So on RSK, a gwei is 10-9 RBTC, equivalent to 0.1 sats.
The default price of gas on RSK 0.06 Gwei. The price of gas may vary some with the level of activity on the network.
Consider the following example in which we explain everything that happens during a contract interaction on the RSK network.
Each transaction is weighted and paid by these parameters:
- Gas Price (gwei): The price per unit of gas consumed that you are willing to pay. In RSK, our default is 0.06 Gwei, which says that you are willing to pay 0.00000000006 of RBTC per each needed unit of gas that is required to make the transaction happen. Sending someone some RBTC will cost a small amount, such as 21 000 units, where each interaction with a smart contract adds to the cost.
- Gas Limit: The upper limit on the number of gas units the user authorizes to pay for a transaction. The number of gas units is multiplied by the price (gwei) you are willing to pay to determine the maximum fee the user is authorizing.
- Gas Units: The actual number of gas units used by the smart contract interaction triggered by the transaction.
The number of gas units used (Gas Used) multiplied by the price (Gas Price) you are willing to pay in the native asset determines the final cost of the transaction.
¶ Example
Transaction example link from the RSK explorer: https://explorer.rsk.co/tx/0x35f7318d4c1def4301f0b4a3087d3f2da4c35b6d5c96a67b01a682bdec072773?__ctab=Transaction
- Gas Price = 0.000000000065164 RBTC = 0.065164 Gwei
- Gas Limit = 1,500,000 units (The maximum we allowed to spend for the transaction. If the number of units needed for fulfilling the transaction is higher than our limit, the transaction will fail due to a lack of gas.)
- Gas Used = 1,103,764 units (The final amount of units spent by the function triggered by the transaction)
- The final cost of the transaction in RBTC is then calculated as:
- Gas Used * Gas Price = 1,103,764 * 0.000000000065164 (RBTC) = 0.000071925677296 RBTC
- For bitcoin with the valuation of 57,500 USD for BTC => Transaction Fee in USD = 0.000071925677296 * 57,500 = 4.13 USD
¶ Difference between GWEI use on RSK and Ethereum
On Ethereum, one ETH = 1018 Wei = 109 GWei, whereas on RSK one RBTC = 1018 Wei = 109 GWei.
A persistent problem with Ethereum is that the price of gas constantly fluctuates. When the Ethereum network is congested thanks to heavy use, users raise the gas price to increase the priority for their transaction and often pay an exorbitant fee to include their transaction in the next ETH block.
The gas price on RSK is much more stable, so a Gas Price is set at 0.065 GWEI.
