Lending Rate
In one sentence
Lending rate, also called supply APY, is the variable yield earned by depositors on protocols like Aave, Morpho, or Euler. It rises when more of the supplied asset is borrowed.
What it actually means
When you deposit USDC into Aave, you are lending it to borrowers in that market. Borrowers pay interest. Most of that interest flows back to suppliers, prorated by the share of the pool they own. The lending rate is the annualized yield you earn on your deposit, denominated in the same asset.
It is variable. Unlike a fixed-yield instrument, the rate updates every block based on the utilization of the market.
How it is calculated
Lending rate is a function of utilization (the fraction of supplied assets currently borrowed). Most protocols use a piecewise interest rate model with a "kink":
- Below the kink (typically 80%–90% utilization): rate rises slowly with utilization.
- Above the kink: rate rises steeply to incentivize repayments and new supply.
- Supply APY ≈ borrow APY × utilization × (1 − reserve_factor).
Why it matters to you
Your projected yield can change quickly. A market with 70% utilization can spike to 95% in hours during a leverage cycle, briefly pushing supply APY from 3% to 20% — or dropping back to 1% when demand collapses. If you parked stables expecting a steady 5%, you should know when the assumption breaks.
- Sharp drop in rate: reconsider whether the position still beats its alternatives.
- Sharp rise: someone is paying a lot to borrow — usually meaningful, sometimes a security signal.
- Rate going to zero: deposits are being unused; consider rotating capital.
Real example
In early 2024, USDC supply APY on Aave V3 mainnet oscillated between 1.5% and 9% within the same week as leveraged ETH plays opened and closed. A passive lender who set up expecting 5% saw their projected annual yield collapse to 1.8% and then spike to 8.1% in the span of 72 hours.
Variable vs fixed yield
Lending rates on Aave-style protocols are variable by construction. If you want fixed yield on the same underlying, you can use Pendle PT or yield strips that lock in a rate for a defined period. The trade-off is liquidity: locked positions have an exit price set by the market, and that price moves when implied rates change. For passive holders who want predictability and accept the variable risk, base lending is the simpler option. For users who want to express a view on rates direction, fixed-yield instruments are the tool.
Reserve factor and protocol revenue
Not all interest paid by borrowers reaches suppliers. Each market has a reserve factor (typically 10%-25%) that diverts a slice of borrow interest to the protocol treasury. This is why supply APY is always lower than borrow APY at the same utilization. The reserve factor is set by governance and can be changed, which materially affects supplier yields. Worth knowing for long-duration positions.
How Otomato monitors it
Otomato tracks supply APY on every asset you have lent across Aave, Morpho, and Euler. You get alerted when the rate drops meaningfully below your entry expectation or when it spikes, so you can decide whether to rotate. Rate changes that are too small to matter never reach you.
Related terms
Monitor this in your portfolio
Otomato detects your positions automatically and alerts you only when something material changes. No setup, no signatures.
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