Lending USDC on Aave: my real yield after gas fees

The Aave USDC yield is right there on the app. It tells you what the lent USDC earns, not what you earn: Aave leaves out the network fees, the gas. I lent 94 USDC in January 2025 and got 97.10 USDC back nine months later. I thought I’d made 3%. Once I added up the gas, I had lost almost 4%.

How lending USDC on Aave works

You deposit USDC into an Aave pool, other users borrow it against collateral, and you collect their interest. A full loan takes three transactions, each paid in ETH:

1. Approval: you allow Aave to pull your USDC. It’s easy to forget in your records.
2. Deposit: your USDC goes into the pool. In return you get aUSDC, a receipt token always worth 1 USDC.
3. Withdrawal: you hand back your aUSDC and get your USDC back, interest included.

Between deposit and withdrawal, no transaction happens: your aUSDC balance just grows, block after block (Aave’s documentation).

The rate moves: the more of the pool’s USDC is borrowed, the more lenders earn (Aave’s help center).

Aave’s real yield, after gas

Annualized real yield = (interest − gas fees) ÷ amount lent × 365 ÷ days

Interest is what you withdrew minus what you deposited. Gas for the three transactions is converted to dollars at the ETH price on the day you paid it.

My 94 USDC loan, line by line

Gross yield: 3.10 ÷ 94 × 365 ÷ 282 = +4.27% a year. Real yield: (3.10 − 6.80) ÷ 94 × 365 ÷ 282 = −5.09% a year, or −3.93% over the life of the loan.

In a spreadsheet

Deposit and withdrawal dates in B2 and C2, amounts deposited and withdrawn in D2 and E2, total gas in dollars in F2:

If you keep your books in another currency, convert both the interest and the gas. These columns can live on their own tab of a crypto portfolio tracker spreadsheet.

Break-even: how many days to earn back the gas

Gas is fixed: depositing 94 or 94,000 USDC takes the same transaction. Interest scales with the amount. So run this before you lend:

days to earn back gas = gas × 365 ÷ (amount lent × annual rate)

At 4% a year, with three gas costs I actually paid for a full loan:

Arbitrum is a “layer 2” network built on top of Ethereum, where gas costs cents. On Ethereum, gas depends on timing: my 2026 loans cost me between $0.16 and $0.60.

How my other loans did

My 94 USDC loan is the worst by far. Across my thirteen DeFi loans with a known result (Aave, Compound, Maple, Morpho, other vaults), gas took 12% of the interest. That one small loan paid 58% of that gas on its own: without it, gas would have taken 5%.

The last row shows the other trap, duration: even with low gas, a four-day loan hands almost everything it earns back to the network. I made six cents.

Where a spreadsheet breaks down

A real DeFi portfolio gets messy fast:

• interest is invisible until you withdraw: for an open position, you have to look up your aUSDC balance in your wallet by hand;
• several deposits, one partial withdrawal: you have to pick which one you’re closing, usually first in, first out, and split the withdrawal’s gas between them;
• gas is paid in ETH: you need the amount and that day’s price for every transaction, and nothing links the approval to the loan except the date;
• vaults: on Maple or Morpho you get shares whose value goes up, and only their price tells you the interest.

Add a chain per protocol, and the spreadsheet becomes a job of its own.

Crypto Master reads your wallet from its public address, with no recovery phrase (what we keep, and what we never ask for). Its DeFi operations page attaches all three transactions to each Aave, Compound or Maple loan, with gas valued at that day’s price and split pro rata across several deposits. Yield is computed after gas, and interest on an open position is read from the chain. Uniswap and Aerodrome liquidity positions are matched too.

In the made-up demo portfolio, this loan shows 4.10% a year gross. Gas took three quarters of it, leaving +0.99% a year. The free plan covers 3 connected accounts and 500 transactions.

Frequently asked questions

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