Real loan rate: when inflation works in your favor

Real loan rate: the missing piece in every buy or rent decision

When people compare buy or rent, they usually look at the mortgage rate their bank offers: 3.2 %, 3.6 %, 4 %… But that is only the nominal rate. To really understand the cost of a mortgage, especially in an inflationary environment, you must look at the real interest rate: the mortgage rate adjusted for annual inflation.

Since 2022, inflation in Europe has often moved between 4 % and 6 %, while mortgage rates have been around 3.5 %–4 %. That means that in some situations, your real rate is close to zero, or even negative. In other words, inflation is slowly eating away the real value of your debt.

This article explains, with concrete numbers, how this mechanism works and how to integrate it into a buy or rent simulation, focusing on two key parameters of our simulator: taux_pret (loan rate) and inflation_annuelle (annual inflation).

Nominal vs real interest rate: the key formula

The nominal rate is what you see in your mortgage offer, for example 3.6 % fixed for 25 years. The real rate adjusts this figure for inflation, which reduces the purchasing power of money over time.

The simplified formula

A widely used approximation is:

Real rate ≈ Nominal rate – Annual inflation

Example:

• Loan rate (taux_pret): 3.6 %
• Annual inflation (inflation_annuelle): 4.5 %

Then:

Real rate ≈ 3.6 % – 4.5 % = –0.9 %

A negative real rate means that, in terms of purchasing power, your debt is getting cheaper over time: the euros you repay in 15 or 20 years are worth less than the euros you borrowed today.

A simple numerical example

Assume:

• Loan amount: €200,000
• Nominal mortgage rate: 3.6 %
• Term: 25 years
• Average annual inflation: 4 %

The monthly payment (excluding insurance) is about €1,012. In nominal euros, that never changes. In real terms, corrected for inflation, the burden drops over time:

• Year 1: €1,012 in today’s money
• Year 10: adjusted for 4 % inflation per year, the effort is equivalent to roughly €680 in today’s euros
• Year 20: it is equivalent to under €460 in today’s euros

This is central in the buy or rent comparison: the tenant pays rent that typically follows inflation (via rent indexation), while the borrower pays fixed nominal payments whose real weight declines year after year.

Inflation, real rate and the buy or rent trade-off

Saying that inflation can work « in favor » of borrowers does not mean buying is always better than renting. It means that, for a given taux_pret, a higher inflation_annuelle lowers the real cost of your mortgage, which changes the arithmetic of buy or rent.

Scenario 1: low inflation, high mortgage rate

Assumptions:

• Mortgage rate: 4.5 %
• Annual inflation: 1.5 %
• Investment return if you rent and invest: 4 % (diversified ETFs over the long term)

Real mortgage rate ≈ 4.5 % – 1.5 % = 3 %. Your investments may earn about 4 % nominal, or ≈ 2.5 % real. In this context, debt is genuinely expensive in real terms, and the rent + invest strategy can look very attractive.

Scenario 2: high inflation, moderate mortgage rate

Assumptions:

• Mortgage rate: 3.6 %
• Annual inflation: 5 %
• Investment return: 4 %

Real mortgage rate ≈ 3.6 % – 5 % = –1.4 %. Your mortgage becomes « cheap » in real terms: inflation erodes the real value of your outstanding debt faster than interest accumulates.

At the same time, your investments at 4 % with 5 % inflation have a real return of ≈ –1 %. Your money in financial markets is also losing purchasing power, even if it may still do better than low-yield savings accounts.

In that case, buying with a mortgage whose nominal rate is below inflation can be advantageous on paper, but it is still only one variable in the full buy or rent comparison.

Using the real rate inside a buy or rent simulator

On our simulator buy-or-rent.net (and its French version acheter-ou-louer.com), you can explicitly set:

• taux_pret: the nominal mortgage rate (often around 3.6 % today for 20–25 years, depending on the market)
• inflation_annuelle: your assumption for future inflation (2 %, 3.5 %, 5 %, etc.)

By adjusting these two inputs, you see the impact on:

• the real total cost of your mortgage
• how your monthly payments feel over time in real terms
• the comparison against the rent + invest scenario

Full example: €250,000 over 25 years

Buying scenario:

• Property price: €250,000
• Loan rate (taux_pret): 3.6 %
• Term: 25 years
• Down payment: €20,000
• Annual inflation (inflation_annuelle): 4 %

The monthly payment (excluding insurance) is about €1,265.

In nominal terms, total interest paid is roughly €125,000 over 25 years. But in real terms, once you discount future payments at 4 % inflation per year, the effective cost is significantly lower because the last payments have much less purchasing power.

Renting scenario:

• Initial rent: €1,000 per month
• Annual rent increase: linked to an inflation index, assume 3.5 % per year
• Invested savings (down payment + monthly difference vs owning): €20,000 initial + monthly contributions
• Investment return: 4.5 % nominal

Here, your rent broadly follows inflation. After 25 years at 3.5 % annual increases, your monthly rent can exceed €2,400. The real burden stays roughly stable, but the nominal cash outflow grows strongly.

The simulator compares:

• the future net value of your housing wealth (property value minus remaining debt, possibly after selling)
• the future value of your investment portfolio if you keep renting

The real rate of your mortgage, driven by the combination of taux_pret and inflation_annuelle, sits at the core of that comparison.

When inflation becomes a borrower’s ally

1. Fixed payments vs rising income

If your income roughly follows inflation (salary increases, promotions, indexation), your fixed nominal monthly payment becomes easier to bear over time.

Example:

• Monthly payment: €1,200
• Initial net salary: €2,500
• Debt-to-income at the start: 48 %

With 3 % annual salary growth over 10 years, your salary reaches around €3,360. The same €1,200 payment now represents ≈ 36 % of your income. Meanwhile, a tenant is likely paying higher and higher rent every year.

2. Fixed debt vs potentially appreciating asset

If property prices follow inflation over the long run (not guaranteed, especially locally), you have:

• a fixed nominal debt
• an asset (the home) that may rise in value over time

Example over 20 years:

• Purchase price: €250,000
• Average inflation: 3 %
• Property price growth: 2.5 % per year (slightly below inflation)

After 20 years, the property could be worth around €410,000. Your outstanding mortgage balance has fallen every year in nominal euros, and even more in real terms.

Of course, real estate prices can also stagnate or fall, depending on the local market. That is why no buy or rent simulation should assume guaranteed, strong price growth.

Why inflation alone does not make buying automatically better

The fact that inflation lowers the real cost of your mortgage does not erase all the other costs and risks of homeownership.

Additional costs that are not erased by inflation

• Notary fees: 7–8 % of the purchase price in existing properties, 2–3 % in new builds, paid upfront
• Agency fees: typically 3–5 % of the price
• Property tax: from about €450 to more than €5,000 per year depending on the city, with annual reassessments and potential increases
• Borrower insurance: often 0.25–0.45 % of the loan amount per year
• Maintenance and renovation: especially if the energy rating is poor or if energy retrofits are needed

These costs are very real, and while inflation may affect them too, they are not automatically reduced in the same way as the real value of your fixed-rate debt. In a rental situation, many of these expenses are borne by the landlord, not you.

Rate risk and prepayment penalties

If interest rates fall significantly in the future, you may want to refinance or repay early:

• Prepayment penalties: up to 3 % of the remaining principal or 6 months of interest, depending on your contract and local rules
• Refinancing fees and administrative costs

These can eat into the benefit you hoped to gain from a low or negative real interest rate.

Inflation, real rate and financial investments

The buy or rent question is not just about comparing a mortgage with rent. It is also about comparing:

• the real return on your property investment
• the real return on financial investments (ETFs, diversified funds, etc.)

If you remain a tenant and invest your capital, the key question becomes: is the real return on your investment portfolio higher than the real return on the property project (after accounting for price appreciation, costs, and the real rate of your mortgage)?

Example:

• Property project: nominal mortgage rate 3.6 %, inflation 4 %, real rate ≈ –0.4 %
• Gross yield from the property (imputed rent or actual rent if rented out later): 3 % per year
• Estimated net real yield after costs and inflation: around 2 % per year
• Investment portfolio: 6 % nominal, 4 % inflation → 2 % real

Over the long term, you could end up with a similar real return from real estate and from a diversified investment portfolio, but with different types of risk (local housing market risk vs global market volatility).

Testing different inflation scenarios in the simulator

On buy-or-rent.net, you can:

• set your actual taux_pret from the bank (e.g. 3.6 %)
• try several inflation_annuelle values: 2 %, 3 %, 4.5 %, 6 %
• see how the final buy or rent outcome changes

For example:

• At 2 % inflation: real rate ≈ 1.6 %, debt is genuinely costly in real terms
• At 4 % inflation: real rate ≈ –0.4 %, inflation significantly lightens your mortgage burden
• At 6 % inflation: real rate ≈ –2.4 %, but your living costs and property tax are also rising fast

The tool shows, year by year, how your net wealth evolves in both scenarios. You can literally see the impact of the real interest rate and understand when inflation may work for you, and when it is mostly eroding your overall purchasing power.

Conclusion: the real rate is crucial, but not the whole story

The real interest rate on your mortgage, driven by the combination of taux_pret and inflation_annuelle, is a central parameter in any serious buy or rent analysis. When inflation is higher than your nominal mortgage rate, the real value of your debt shrinks over time and buying with a fixed-rate loan can look attractive.

However, the decision still depends on many other factors: job stability, how long you plan to stay, local market conditions, all the additional ownership costs, alternative investment opportunities, and your risk tolerance. There is no universal answer: whether you should buy or rent always depends on your personal situation.

This content is for information only and does not constitute personalized financial advice. To assess your own case with your numbers and your inflation assumptions, the most effective approach is to run a detailed simulation.

Simulate your situation on buy-or-rent.net and test different loan rate and inflation scenarios to see how the real interest rate could work in your favor – or not.