How Mortgage Refinancing Works

Mortgage refinancing — called remortgaging in the UK and Netherlands — replaces your existing mortgage with a new loan, typically to secure a lower interest rate, change the loan term, or release equity. The decision depends on whether the interest saving over the remaining term exceeds the costs of switching. A break-even calculation tells you exactly how many months you need to stay in the property for refinancing to make financial sense.

mortgage refinancing remortgage interest-rate break-even

Quick reference

Break-even formula

Total costs / Monthly saving

Months to recover switching costs

Minimum rate drop

Typically 0,5 to 1%

For refinancing to make sense on standard mortgages

Early repayment charge

1 to 5% of outstanding balance

The largest switching cost — check before calculating

Netherlands penalty calculation

Based on interest rate differential

Boeterente — regulated formula applies

Why people refinance and what it costs

The primary motivation for refinancing is to secure a lower interest rate, which reduces monthly payments and total interest paid over the remaining term. A secondary motivation is to change the loan term — shortening it to pay off the mortgage faster, or extending it to reduce monthly payments during a period of financial stress. Some borrowers refinance to release equity — borrowing additional funds against increased property value.

Refinancing is not free. The costs of switching include an early repayment charge (ERC) on the existing mortgage if you are within a fixed-rate period, valuation fees for the new mortgage, legal or notary fees, arrangement or origination fees on the new product, and in the Netherlands, potential boeterente (penalty interest) calculated on the interest rate differential.

The early repayment charge is typically the largest cost. In the UK, ERCs on fixed-rate mortgages range from 1 to 5% of the outstanding balance in the first years of the fixed period, falling to 1% in the final year. On a 200.000 balance, a 3% ERC costs 6.000. In the Netherlands, the boeterente is calculated differently — it is based on the difference between the original contracted rate and the current market rate for the remaining fixed period, which can be significantly lower or higher than a percentage of the balance.

The existence of costs means refinancing is not always worthwhile. A break-even analysis is required to determine whether the interest saving over the expected remaining period in the property justifies the switching costs.

The refinancing break-even calculation

Formula

\text{Break-even months} = \frac{\text{Total Switching Costs}}{\text{Monthly Payment Saving}}

Divide the total cost of switching (ERC plus all fees) by the monthly saving in mortgage payment. The result is the number of months before refinancing starts saving you money. If you expect to stay in the property for longer than the break-even period, refinancing makes financial sense.

Total Switching CostsEarly repayment charge plus valuation fee plus legal fees plus arrangement fee on new mortgage

Monthly Payment SavingCurrent monthly payment minus new monthly payment at the lower rate on the same remaining term

Break-even monthsThe minimum period you must stay in the property for refinancing to be worthwhile

When refinancing does not make sense

Refinancing makes sense when the break-even period is comfortably within the time you plan to remain in the property and when the rate saving is meaningful. Several situations make refinancing uneconomical.

If you are near the end of a mortgage term, the interest component of each payment is already small. Refinancing costs may exceed the total remaining interest anyway. On a 25-year mortgage with only 3 years remaining, the balance is low and the interest cost is minimal — refinancing costs would rarely be justified.

If the early repayment charge is very high and the rate drop is small, the break-even period may extend beyond the likely property holding period. A 5.000 ERC with a 100 per month saving takes 50 months (over 4 years) to break even — not worthwhile if you plan to move within 3 years.

In a rising rate environment, refinancing from a fixed rate to a lower fixed rate may be impossible, and refinancing to a variable rate creates rate risk. The analysis must also consider the rate available at refinancing — if rates have risen since the original mortgage was taken out, refinancing may produce a higher rate despite the ERC being paid.

Worked examples

Example 1Standard refinancing at end of fixed period

Result: Monthly saving: 131 | Break-even: 11,5 months | Total saving over remaining term: ~25.000

Current payment: 180.000 x amortization factor (4,5%, 264 months) = approximately 1.063 per month. New payment: 180.000 x amortization factor (3,2%, 264 months) = approximately 932. Monthly saving: 131. Break-even: 1.500 / 131 = 11,5 months. Over 22 years remaining: total saving approximately 131 x 264 - 1.500 = 34.584 - 1.500 = 33.084. This is clearly worthwhile.

Example 2Mid-fixed-period refinancing with ERC

Given: Balance: 220.000 | Current rate: 5% (2 years remaining on fix) | New rate: 3,5% | ERC: 2% of balance | Other costs: 2.000

Result: ERC: 4.400 | Total costs: 6.400 | Monthly saving: 167 | Break-even: 38 months

ERC: 220.000 x 2% = 4.400. Total costs: 4.400 + 2.000 = 6.400. Current payment (approximate at 5%, 20 years remaining): 1.452. New payment (3,5%, 20 years): 1.276. Monthly saving: 176. Break-even: 6.400 / 176 = 36 months. If staying for 5+ years, break-even of 36 months is acceptable. But with 2 years left on the current fix, waiting for the natural end of the fixed period would avoid 4.400 in ERC and still allow switching at a competitive rate.

Example 3Rate reduction too small to justify costs

Given: Balance: 150.000 | Rate drop: 0,3% (from 4,2% to 3,9%) | ERC: 1,5% | Other costs: 1.800

Result: ERC: 2.250 | Total costs: 4.050 | Monthly saving: 26 | Break-even: 156 months (13 years)

ERC: 150.000 x 1,5% = 2.250. Total costs: 4.050. Payment saving at 0,3% rate reduction on 150.000 (20 years): approximately 26 per month. Break-even: 4.050 / 26 = 156 months. A 13-year break-even makes this refinancing completely unviable unless planning to stay for the remainder of the mortgage. A 0,3% rate drop rarely justifies switching costs when an ERC applies.

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Break-even months by rate drop and switching cost

Monthly saving from rate drop	Costs 2.000	Costs 4.000	Costs 6.000	Costs 10.000
50/month	40 months	80 months	120 months	200 months
100/month	20 months	40 months	60 months	100 months
150/month	13 months	27 months	40 months	67 months
200/month	10 months	20 months	30 months	50 months
300/month	7 months	13 months	20 months	33 months
400/month	5 months	10 months	15 months	25 months

Common mistakes when refinancing

✗ Not checking the early repayment charge before calculating savings

✓ The ERC is almost always the largest switching cost and can entirely eliminate the benefit of a lower rate. Check the ERC amount (usually stated in the mortgage offer as a percentage of the outstanding balance in each year of the fixed period) before doing any other calculation. The ERC defines whether early refinancing is viable at all.

✗ Extending the mortgage term to reduce payments without calculating total cost

✓ Refinancing to a lower rate but extending the term may reduce monthly payments while increasing total interest paid. On a 200.000 balance with 15 years remaining, refinancing to a new 25-year mortgage at the same rate reduces monthly payments but adds 10 years of interest payments. Always calculate total interest paid under both options.

✗ Only comparing monthly payments rather than total cost over the remaining term

✓ The monthly payment comparison ignores the timing and amount of costs. Two mortgages with the same monthly payment but different upfront costs and remaining terms have very different total costs. Calculate total cost (all payments plus upfront costs) over the remaining holding period for a proper comparison.

Methodology

Monthly payment calculations use the standard amortization formula. Break-even calculated as total switching costs divided by monthly payment saving. Total saving calculated as monthly saving multiplied by remaining term in months minus switching costs. Netherlands boeterente calculated using the regulated formula based on interest rate differential and remaining term.

Refinancing calculations are estimates. Actual switching costs vary by lender, product and credit profile. ERC amounts and calculation methods are specified in the original mortgage agreement. Always obtain specific figures from your current lender before deciding to refinance.

Cite this guide

APAMLAChicago

https://calquify.com/guides/how-mortgage-refinancing-works

Last updated: May 2026

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Frequently asked questions

When is the best time to refinance a mortgage?

The best time to refinance is at the natural end of a fixed-rate period, when no early repayment charge applies. Most fixed-rate mortgages allow switching at the end of the fixed period — often with a 6-month window before the period ends — without any exit penalty. This is when the break-even calculation is most likely to be favourable. Refinancing mid-fixed-period only makes sense when the rate saving is very large and the remaining fixed period is long enough that the ERC is overcome within the expected property holding period.

Does refinancing affect your credit score?

Applying for a new mortgage creates a hard credit enquiry which temporarily reduces your score by a small amount, typically 5 to 15 points, recovering within 12 months. If you apply to multiple lenders within a short period (usually 14 to 45 days depending on the scoring model), these are often treated as a single enquiry for mortgage purposes. Closing the old mortgage does not directly harm your score. The new lower payment may improve your debt-to-income ratio over time, which is positive for creditworthiness.

Can I refinance to access equity in my property?

Yes — this is called a cash-out refinance or equity release remortgage. If your property has risen in value, you can refinance for a larger amount than the existing mortgage balance and receive the difference in cash. The LTV must remain within acceptable limits (typically 80 to 85% maximum for mainstream lenders). The released equity is treated as additional borrowing and increases your monthly payment. Compare the rate on a cash-out refinance against the rate on a separate personal loan — the mortgage rate is usually lower, but you are securing the borrowing against your home.

Sources & References

› Investopedia — Refinancing Retrieved 2026-05-18

› Hypotheekshop NL — Oversluiten hypotheek Retrieved 2026-05-18

Formula based on standard mathematical and financial methods. Results are for informational purposes. Last reviewed May 2026. Version 1.