What Are Supply Rates in Crypto Lending?

What Are Supply Rates in Crypto Lending?

The supply rate is the annual percentage yield (APY) that lenders earn when they deposit assets into a DeFi lending protocol. When you supply cryptocurrency to a lending pool, borrowers pay interest to use those funds, and the supply rate represents your share of that interest income.

Understanding supply rates is fundamental to making informed decisions about where to deploy your capital in DeFi. This guide explains how supply rates work, what determines them, and how to evaluate them across different protocols.

How Supply Rates Work

At a high level, crypto lending follows a familiar pattern: depositors supply funds, borrowers pay interest to use those funds, and the interest is distributed to depositors as yield.

The Basic Flow

1. You deposit an asset (say, USDC or wBTC) into a lending protocol like Aave, Compound, or Morpho.
2. Borrowers take loans from the pool by posting collateral and paying an ongoing interest rate.
3. The protocol distributes a portion of the interest paid by borrowers to suppliers. This is your supply rate.
4. You earn yield continuously, typically compounding automatically.

Your supply rate is not a fixed number promised by the protocol. It fluctuates constantly based on market conditions — specifically, how much of the supplied liquidity is being borrowed at any given moment.

The Relationship Between Supply Rate and Borrow Rate

Supply rates and borrow rates are two sides of the same coin. The borrow rate is what borrowers pay; the supply rate is what lenders earn. However, the supply rate is always lower than the borrow rate. This is because:

• The protocol takes a cut. Most lending protocols charge a spread (sometimes called a reserve factor) — a percentage of the interest paid by borrowers that goes to the protocol treasury rather than to suppliers.
• Not all supplied funds are borrowed. If only 60% of the pool is borrowed, the interest from that 60% is spread across 100% of suppliers, diluting the effective rate.

The Formula

A simplified version of the supply rate formula looks like this:

Supply Rate = Borrow Rate x Utilization Rate x (1 - Reserve Factor)

This formula reveals the three key variables that determine what you earn as a lender.

What Determines Supply Rates?

Utilization Rate

The utilization rate is the percentage of the total pool that is currently being borrowed. It is the single most important factor driving supply rates.

• High utilization (e.g., 85%) — Most of the pool is borrowed, so there is a lot of interest being generated and distributed to suppliers. Supply rates are higher.
• Low utilization (e.g., 20%) — Most of the pool sits idle, earning nothing. The interest from the small borrowed portion is spread across all suppliers, resulting in low rates.

For example, if the borrow rate is 10% and utilization is 80%, suppliers effectively earn interest on 80% of the pool. If utilization drops to 30%, the same borrow rate produces much less income for suppliers.

Interest Rate Model

Every lending protocol uses an interest rate model — a set of rules (encoded in smart contracts) that determines how borrow rates change based on utilization. Most protocols use a "kinked" model with two slopes:

• Below the optimal utilization (typically 70-90%): Borrow rates increase gradually as utilization rises.
• Above the optimal utilization: Borrow rates increase sharply, incentivizing new suppliers to deposit and existing borrowers to repay.

This kinked design creates a natural equilibrium. When too much is borrowed, rates spike, which attracts new capital and discourages borrowing — pushing utilization back toward the optimal range. Supply rates follow borrow rates, so they spike and fall in the same pattern.

Reserve Factor

The reserve factor is the percentage of interest that the protocol keeps for its treasury. A higher reserve factor means less interest flows to suppliers:

• Reserve factor of 10% — Suppliers receive 90% of the interest generated.
• Reserve factor of 30% — Suppliers receive only 70%.

Reserve factors vary by protocol and by asset. Riskier assets often have higher reserve factors to build up a safety buffer for the protocol.

Market Conditions

Broader market dynamics affect supply rates in less direct but significant ways:

• Bull markets tend to increase borrowing demand (traders want leverage), which pushes utilization and supply rates higher.
• Bear markets often see reduced borrowing demand, leading to lower utilization and supply rates.
• Volatile periods can cause temporary spikes in borrow demand (and therefore supply rates) as traders adjust positions.
• Token incentives — Some protocols distribute governance tokens to suppliers on top of the base supply rate, effectively boosting the total APY. These incentives can be substantial but are not guaranteed to continue.

Supply Rate vs. APY vs. APR

You will encounter several terms when looking at lending rates:

APR (Annual Percentage Rate)

The simple interest rate without compounding. If you earn 5% APR on $1,000, you earn $50 over a year.

APY (Annual Percentage Yield)

The effective interest rate including compounding. Because DeFi lending protocols typically compound interest continuously (or at least very frequently), the APY is slightly higher than the APR. A 5% APR compounds to approximately 5.13% APY.

Base Rate vs. Total Rate

Many protocol dashboards show both a "base" supply rate (the interest from borrowers) and a "total" rate that includes token incentive rewards. Always check which figure you are looking at — token incentives can change or end abruptly.

How to Compare Supply Rates Across Protocols

Not all supply rates are created equal. Here is what to consider when comparing:

Look at Historical Rates, Not Just Current Rates

A protocol might show a high supply rate right now, but if it has been low for the past month, the current spike may be temporary. Many analytics platforms show 7-day and 30-day average rates, which give a more realistic picture.

Factor in the Reserve Factor

A protocol with a lower reserve factor passes more interest to suppliers. If two protocols have the same borrow rate and utilization, the one with the lower reserve factor will offer a higher supply rate.

Check the Utilization Trend

If utilization is near the kink point and trending upward, supply rates may increase. If utilization is falling, rates are likely to drop.

Consider Protocol Risk

A small, unaudited protocol might offer higher supply rates, but the smart contract risk may not justify the additional yield. Established protocols with extensive audit histories generally offer more security, even if rates are slightly lower.

Aggregate and Compare

Platforms like Borrow by Sats Terminal aggregate lending rates across multiple protocols, allowing you to see supply (and borrow) rates side by side. This saves time and helps you make data-driven decisions about where to deploy your assets. Borrow's primary lens is the borrow side of that comparison — finding the cheapest Bitcoin-backed loan across Aave v3, Morpho Blue, and CeFi venues — but the same rate visibility is just as useful for suppliers trying to figure out which protocols are paying out the most.

Supply Rates for Different Asset Types

Supply rates vary significantly by asset type:

Stablecoins (USDC, USDT, DAI)

Stablecoins typically have the highest and most consistent supply rates because they are the most borrowed assets in DeFi. Borrowers use stablecoins for leveraged trading, yield farming, and real-world payments. Supply rates for major stablecoins often range from 3% to 15% depending on market conditions.

Major Cryptocurrencies (ETH, wBTC)

Supply rates for ETH and Bitcoin tend to be lower (often 0.5% to 5%) because borrowing demand for these assets is lower. Most borrowers want to borrow stablecoins against crypto collateral, not borrow the crypto itself.

Long-tail Assets

Smaller or newer tokens may have high supply rates but come with significantly higher risk — low liquidity, volatile utilization, and greater smart contract risk.

Practical Tips for Maximizing Supply Rates

Diversify Across Protocols

Spreading your deposits across multiple lending protocols reduces smart contract risk and allows you to capture the best rates from each platform.

Monitor Rate Changes

DeFi supply rates are not fixed. Set up alerts or check regularly to ensure you are still earning competitive rates. If rates drop significantly on one platform, it may be worth migrating to another.

Consider Gas Costs

On Ethereum mainnet, gas fees for depositing and withdrawing can eat into your yield, especially for smaller positions. Layer 2 networks and alternative chains often have lower transaction costs, making frequent rate optimization more practical.

Understand the Risks

Higher supply rates often come with higher risk. Before chasing yield, make sure you understand why a particular rate is elevated — is it because of genuine borrowing demand, or because the protocol is using unsustainable token incentives to attract deposits?

Conclusion

Supply rates in crypto lending reflect the real-time economics of borrowing and lending in DeFi. They are driven primarily by utilization rates, shaped by interest rate models, and tempered by reserve factors. Understanding these mechanics helps you evaluate where to supply your assets, compare protocols intelligently, and set realistic expectations for the yield you can earn. Tools like Borrow by Sats Terminal make it straightforward to compare supply and borrow rates across the DeFi landscape, so you can put your capital to work where it earns the most.