There are two primary reasons why you might receive a gas estimation error.
If you see a gas estimation error, your transaction will most likely fail.
Error when trying to send funds
You will receive an error if your gas token balance is too low to cover the gas limit. You will also see an error if you are trying to send more tokens that you currently hold in your wallet.
Error when interacting with a DApp
If a DApp’s estimation fails for whatever reason you could receive an inaccurate estimation. Most often the gas amount will be way too high.
Please double check the gas amount before submitting a transaction. A typical smart contract transaction should cost between 70,000 and 200,000 gas.
An error could also occur when your gas token balance is too low to cover the gas limit.
Gas limit vs. actual gas usage
When sending a transaction you will always specify the gas limit which is the most gas your transaction may consume. It may end up using significantly less. However, your transaction will fail if you set the gas limit too low. A regular ETH transfer on mainnet should pass with a gas limit of 21,000. A transfer of an ERC token or a smart contract interaction like a swap could require significantly more than that.
Here is a good resource where you can check how much various interactions will cost on the Ethereum mainnet: https://etherscan.io/gastracker
How do I reduce the costs?
You can try making your transactions at times with lower traffic. Alternatively, you can check out some other networks with significantly lower fees that offer similar DApps and functionalities.
Some of these are:
You can use the built-in bridges on BlockWallet to transfer your funds from Ethereum to other networks.