WHY BANKS DON'T NEED TO CHARGE YOU MUCH TO MAKE MONEY FROM YOUR MONEY
Your bank account might pay you almost nothing. That doesn't mean your money is doing nothing for the bank.
Imagine you keep:
€10,000
in a normal bank account.
The bank pays you:
0.5% interest
You receive about:
€50 per year
It might feel like the bank is barely doing anything with your money.
But from the bank's perspective, your deposit can be extremely valuable.
YOUR DEPOSIT IS FUNDING
When you deposit €10,000, the bank records:
+€10,000 cash/reserves or other assets
and
+€10,000 deposit liability to you
The bank owes you that €10,000.
But it doesn't necessarily leave the entire amount sitting untouched in a vault.
Banks manage their balance sheets using deposits alongside other sources of funding.
And deposits can be particularly attractive because they are often relatively cheap and stable funding.
The ECB calls this the deposit franchise: the economic value banks obtain from attracting and retaining low-cost deposits.
THE BANK DOESN'T NEED TO PAY YOU MUCH
Suppose, purely as an illustration, a bank pays you:
0.5%
on your deposit.
But it earns:
4.5%
on part of its interest-earning assets.
The difference is:
4.5% − 0.5% = 4 percentage points
That difference is part of the bank's net interest income.
It isn't pure profit.
The bank still has:
Employees
Branches
Technology costs
Regulatory costs
Funding costs
Credit losses
Capital requirements
Other operating expenses
But the basic business logic is simple:
Pay less on funding → earn more on assets → keep the spread after costs and losses.
THIS IS WHY YOUR SAVINGS ACCOUNT CAN BE VALUABLE
You might think:
"I'm only keeping €10,000 there."
But banks don't necessarily look at your account in isolation.
They manage millions or billions of euros across thousands or millions of customers.
Imagine a bank has:
€10 billion
of customer deposits.
If the average cost of those deposits is relatively low, that can provide a substantial funding base.
The ECB notes that overnight deposits in particular tend to be less sensitive to changes in market interest rates than other funding sources, which can support banks' net interest income.
A tiny difference multiplied across a huge balance sheet can become significant.
THEN THE BANK LENDS
A bank can use its balance sheet to provide loans.
For example:
Your deposit
↓
Bank funding
↓
Mortgage / business loan / consumer loan
↓
Interest paid by borrower
The borrower might pay substantially more interest than the bank pays you on your deposit.
That difference contributes to the bank's net interest income.
This is one of the central mechanics of traditional banking.
THE STRANGE PART IS THAT YOU AND THE BORROWER CAN BOTH BE CUSTOMERS
Imagine:
You deposit:
€10,000
Another customer takes a loan.
The bank doesn't need to tell you:
"We're going to use your exact €10,000 to finance this person's mortgage."
Banking doesn't work as a one-to-one matching system.
The bank manages its overall balance sheet.
Deposits are liabilities.
Loans are assets.
The bank earns income from its assets while managing the cost of its liabilities.
WHY DON'T BANKS JUST PAY YOU THE SAME RATE?
Because the spread is part of the business model.
Suppose market rates rise.
A bank might be able to earn more on loans and other interest-bearing assets.
But it doesn't necessarily increase the interest paid on every existing deposit by the same amount or at the same speed.
The ECB has documented this incomplete pass-through: deposit rates often respond more slowly than market rates, particularly for overnight deposits.
That difference can increase the bank's deposit spread.
THIS BECOMES VERY IMPORTANT WHEN INTEREST RATES RISE
Imagine rates move from:
1% → 4%
A bank's lending rates may adjust relatively quickly.
But the rate paid on an ordinary overnight deposit might move much more slowly.
So the bank's economics can temporarily improve.
That's one reason the ECB has described deposits as an important source of bank income during periods of rising interest rates.
But the effect isn't permanent or identical for every bank.
Competition can force banks to offer higher deposit rates.
Customers can move their money.
Banks can have different loan portfolios and funding structures.
AND THEN THE OPPOSITE CAN HAPPEN
Suppose interest rates fall sharply.
The bank may earn less on new loans and other assets.
But there is a limit to how far it can reduce the interest paid on deposits.
If deposit rates are already close to zero, there isn't much room left to cut them.
The ECB has noted that this can compress banks' net interest margins in very low-rate environments.
So banks don't automatically make more money whenever rates rise or whenever rates fall.
It depends on how quickly different parts of their balance sheet reprice.
THE BANK ALSO MAKES MONEY IN OTHER WAYS
Interest isn't the whole business.
Banks can also earn:
The ECB reported in 2026 that euro-area banks' profitability also relies significantly on non-interest income, particularly as net interest income changed with the rate environment.
So a bank isn't simply:
deposits → loans → profit
It's a much larger financial business.
YOUR MONEY ISN'T "SITTING THERE"
This is perhaps the most important mental shift.
When you see:
€10,000
in your banking app, it is tempting to imagine €10,000 physically sitting somewhere with your name on it.
But your deposit is a liability of the bank.
The bank owes you that amount.
At the same time, the bank has assets and funding arrangements supporting its balance sheet.
Your deposit can therefore be valuable to the bank even if the interest rate you receive looks tiny.
WHY BANKS CARE SO MUCH ABOUT DEPOSITS
A stable deposit base can be a competitive advantage.
The ECB's research describes a strong deposit franchise as an economic asset because it can provide banks with stable, low-cost funding.
That means a bank isn't necessarily trying to make a huge amount of money from your individual €10,000.
It's trying to build a large, stable funding base.
Then:
Millions of deposits
↓
Large funding base
↓
Loans + securities + other assets
↓
Interest income
↓
Minus interest paid
↓
Minus costs + losses
↓
Bank profit
THE REALLY INTERESTING PART
This explains why a bank might advertise:
"0.25% interest on your current account."
while simultaneously charging someone else:
4%, 5%, 6% or more
for borrowing.
The difference isn't automatically the bank's profit.
But that difference is part of the economic engine behind traditional banking.
And the larger the bank's balance sheet becomes, the more important even a relatively small percentage spread can become.
MAACAT PERSPECTIVE
Your money doesn't have to earn you much for it to be useful to a bank.
That's the strange part.
A deposit can be valuable because it gives the bank access to stable, relatively inexpensive funding.
So when you look at your bank account and think:
"They're only paying me 0.5%."
the bank may be looking at something completely different:
"This is a source of funding we can use across a €10 billion balance sheet."
In banking, the interesting number isn't always how much you earn on your money.
Sometimes it's the difference between what your money costs the bank and what the bank can earn with its balance sheet.
