Refinancing your mortgage rate: a complete guide to optimizing your home loan

Why refinancing your mortgage rate is critical in a buy or rent decision

Refinancing your mortgage or renegotiating your rate can create a difference of tens of thousands of euros over the life of a home loan. When you wonder whether you should buy or rent, the key driver is often the loan rate (taux_pret): it determines your monthly payments, total interest paid, and ultimately the profitability of buying versus staying a renter and investing your savings.

Since 2022–2023, mortgage rates in Europe have risen sharply and now hover around 3.5–3.8% over 20 years for strong profiles, compared with 1–1.5% a few years earlier. Refinancing your mortgage rate does not have the same value if you borrowed at 4.5% in 2013 as if you borrowed at 1.2% in 2021. There is no universal answer; it depends on your situation, remaining term, outstanding balance, and objectives (pay off faster, lower monthly payments, invest more, etc.).

This guide focuses on the taux_pret parameter in our buy vs rent simulator and explains how a simple rate change alters the comparison between owning and renting.

Renegotiation vs refinancing: understanding your options

Renegotiating with your current bank

Rate renegotiation means asking your existing bank to lower the interest rate on your current mortgage. Legally, the existing contract is amended rather than replaced.

• Possible costs: renegotiation fees, admin fees, possible guarantee update costs (mortgage, guarantee), but usually no prepayment penalty because the loan is not repaid, it is modified.
• Advantage: simpler process than external refinancing, often cheaper.
• Drawback: the bank is not obliged to accept or to match the best market rate.

Refinancing with a new bank

Refinancing (external buy-back) means a new lender repays your existing mortgage and replaces it with a new loan at a lower rate.

• Prepayment penalties: typically capped at 3% of the outstanding balance or 6 months of interest at the original rate, whichever is lower (depending on your jurisdiction and contract).
• New guarantee / mortgage fees: you may pay for a new mortgage or guarantee and possibly release fees on the old one.
• Arrangement fees: often a few hundred euros.

To know if refinancing is worth it, you must compare the interest savings from the new taux_pret with all these costs. That is exactly what a tool like buy-or-rent.net can help you do when you are arbitraging whether to buy or rent.

The role of the interest rate in the total cost of your mortgage

Basic example: €250,000 over 20 years

Assume a loan of €250,000 over 20 years (240 months), excluding mortgage insurance to isolate the rate effect.

• At 3.6% (approximate current average): monthly payment ≈ €1,470, total interest ≈ €103,000.
• At 2.0%: monthly payment ≈ €1,265, total interest ≈ €53,500.

A difference of 1.6 percentage points leads to about €49,500 more or less interest over 20 years, close to 20% of the loan principal. In a buy or rent comparison, that gap can completely flip the result, especially if, as a renter, you invest your spare cash at a placement rate of 3–5% (for example via ETFs or diversified funds).

Why the remaining term matters

Refinancing or renegotiating your rate is more attractive when:

• your outstanding balance is still high;
• you have many years left on the mortgage.

In the early years, interest makes up a large share of each payment; later, principal dominates. Refinancing a 3.8% loan after 2 years is very different from refinancing after 15 years.

Case study #1: internal rate renegotiation

Initial situation

Assume you:

• Borrowed €280,000 over 25 years (300 months) in 2021.
• Original rate: 1.6%.
• Monthly payment (excluding insurance) ≈ €1,136.
• Total expected interest ≈ €59,000.

In 2024, market rates are around 3.6%. Renegotiating your mortgage rate downward clearly makes no sense here: your rate is already below the market. In a buy vs rent comparison, our simulator with taux_pret = 1.6% will show that buying is highly competitive vs renting, especially if the annual rent increase (linked to inflation) remains around 2–3% per year.

When internal renegotiation becomes relevant

Consider the opposite situation:

• Loan: €220,000 over 20 years.
• Initial rate: 3.9% (loan taken in a high-rate environment).
• Monthly payment ≈ €1,323, total interest ≈ €97,500.

In 2026, rates fall to 2.8%. You ask your bank to renegotiate and it agrees to lower taux_pret to 3.0% for the remaining term.

Assume you have 17 years left and an outstanding balance of €190,000:

• Before renegotiation (3.9%): remaining interest ≈ €67,000.
• After renegotiation (3.0%): remaining interest ≈ €47,000.

Gross savings ≈ €20,000. Even if renegotiation and admin fees cost €1,000–1,500, the operation remains attractive. In a buy or rent comparison, this significantly improves the ownership scenario without altering your rental reference point.

Case study #2: refinancing with a new lender

Initial situation

Assume you:

• Borrowed €300,000 over 25 years at 4.2%.
• Monthly payment ≈ €1,626 (excluding insurance).
• Total expected interest ≈ €188,000.

After 5 years, you have roughly:

• €260,000 outstanding balance.
• 20 years remaining.

A new bank offers to refinance at 2.9% over 20 years.

Refinancing costs

• Prepayment penalty: 3% of €260,000 = €7,800, but compared with 6 months of interest at 4.2%: 260,000 × 4.2% × 0.5 ≈ €5,460. The lower cap applies, so penalty ≈ €5,460.
• New guarantee + arrangement fees: assume €2,000.

Total upfront cost ≈ €7,500.

Interest savings from a lower taux_pret

• Without refinancing: remaining interest over 20 years ≈ €146,000.
• With refinancing at 2.9%: total interest ≈ €86,000.

Gross savings ≈ €60,000. After subtracting €7,500 of costs, net gain ≈ €52,500. Monthly payment drops from about €1,626 to €1,430, roughly €200 less per month.

This lower payment frees up cash you can invest at a placement rate of 3–5%, further improving your wealth in the ownership scenario. In our buy-or-rent.net simulator, you can plug in the new taux_pret and see how your net worth projection over 10, 15 or 20 years compares with staying a renter and investing instead.

How the mortgage rate affects the buy or rent outcome

Renter-investor vs refinanced owner

Imagine the following:

• Current rent: €1,250/month, with annual rent increase of 2.5% (linked to an inflation index).
• Purchase project: apartment for €320,000, with notary / closing costs of 7.5% (existing property) i.e. €24,000.
• Down payment: €40,000.
• Loan amount: €304,000 over 25 years.

Two rate scenarios:

• No refinancing: taux_pret = 4.0%, monthly payment ≈ €1,606.
• Refinance after 3 years: effective average rate cut to about 3.0% for the remaining term, future payment ≈ €1,450.

If you stay a renter, you can invest the difference between your rent and a hypothetical mortgage payment. But if refinancing brings your mortgage payment closer to (or below) your rent, the advantage of the renter-investor strategy shrinks. That is why it is crucial to test multiple taux_pret values in a buy or rent simulator and see from which rate threshold buying becomes competitive.

Don’t forget the parameters surrounding taux_pret

Borrower insurance (taux assurance)

Your insurance rate (commonly 0.25–0.45% of the principal per year) can erode part of your rate savings if you do not renegotiate it. A mortgage going from 4.0% to 3.0% but with insurance rising from 0.25% to 0.45% does not yield the same net benefit as the simple rate difference suggests. Testing both in the simulator gives a more realistic picture.

Inflation and rent escalation

Annual inflation (2–4% in recent years) drives rent increases via official indices. By locking in a lower mortgage rate through refinancing, you stabilize part of your housing costs while rent would continue rising. In a long-term buy or rent comparison, that can make ownership more attractive if inflation stays elevated.

Property tax and its revaluation

As an owner, you pay property tax, which can range from a few hundred to several thousand euros per year depending on the city, and it is often reassessed upward annually. Even if you reduce your taux_pret, this recurring cost must be included in your simulation to compare ownership honestly with renting.

When refinancing your mortgage rate may not be worth it

• You only have 5–7 years left: the interest share in each payment is already small, so the potential savings may not offset fees.
• Your current rate is close to market levels: a 0.2–0.3 point reduction might be too small, especially if your outstanding balance is modest.
• You plan to sell soon (within 3–5 years): upfront refinancing costs may not be amortized.

In these cases, it is safer to run detailed cash-flow simulations than to assume a lower rate is always beneficial.

How to use a buy or rent simulator to test refinancing scenarios

Key steps on buy-or-rent.net

In a tool like buy-or-rent.net you can:

• Enter your current mortgage rate (taux_pret) and outstanding balance.
• Create an alternative scenario with a refinanced taux_pret (for example, 3.0% instead of 4.0%).
• Include prepayment penalties and refinancing fees, either added to the new principal or paid upfront.
• Compare the total cost of ownership (principal + interest + property tax + maintenance) with a renting scenario where you invest your free cash at a chosen investment rate.

You will quickly see how a lower taux_pret changes your projected net worth after 10, 15 or 20 years, and how it affects the answer to the question: should you buy or rent?

Conclusion: refinancing is powerful, but context matters

Refinancing or renegotiating your mortgage rate can cut the cost of your loan by tens of thousands of euros, especially if you have many years and a large balance left. The impact on the buy or rent decision is substantial because a lower taux_pret:

• reduces your monthly payments;
• shrinks total interest paid;
• frees up cash to invest elsewhere;
• makes ownership more competitive relative to renting in the long run.

However, the real benefit depends on your exact parameters (loan size, remaining term, current rate, refinancing costs, and plans to move or sell). This article is for information only and is not personalized financial advice.

To make an informed decision and see whether refinancing improves your ownership scenario versus renting, test different taux_pret assumptions in our simulator: Simulate your situation on buy-or-rent.net.