A growing number of mortgage lenders offer reduced rates for properties with an EPC rating of A or B. The rate differential varies by lender and changes over time, but a reduction of 0.10% to 0.25% is typical for qualifying properties. On a large mortgage with many years remaining, even a small rate reduction produces a total interest saving that can exceed the cost of the improvements needed to reach the qualifying EPC band. This calculator makes that comparison visible and answers the question that most homeowners do not think to ask: is improving my EPC rating before the next remortgage financially worthwhile in its own right?
The calculator takes your outstanding mortgage balance, current rate, remaining term, and the rate differential you expect to achieve, and shows the total mortgage interest saving over the remaining term. It also models the case where the EPC improvements are financed by a home improvement loan: the loan interest cost is shown alongside the mortgage saving so you can see the net position after accounting for both. Green mortgage rates and availability vary by lender and change over time, and all figures are illustrative. The information is general and does not constitute financial or mortgage advice.
At a Glance
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Most green mortgage products that offer a meaningful rate reduction require EPC A or B.
EPC B is the more commonly targeted band because EPC A requires near-perfect insulation and renewable generation, which is not achievable for most existing UK homes without very significant investment. Reaching EPC B from a starting point of D typically requires a combination of two or three measures: loft and cavity wall insulation, plus solar panels or a heat pump. Some lenders accept EPC C for green products, but the differential at that band is typically smaller and fewer products are available.
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Three variables drive the size of the mortgage interest saving: rate differential, outstanding balance, and remaining term.
The saving is approximately proportional to the rate differential, so a 0.1% reduction saves roughly half as much as a 0.2% reduction. The 0.2% default in this calculator is a commonly cited mid-range figure, but actual differentials vary by lender and change over time. The saving also scales with both outstanding balance and remaining term: a £300,000 mortgage with twenty-five years to run produces a much larger saving than a £100,000 balance with five years remaining.
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Financing the improvements with a home improvement loan can still produce a net positive position, because the mortgage saving extends over many more years than the loan term.
A home improvement loan typically carries a higher rate than a mortgage, but the loan runs for three to seven years while the mortgage saving applies over the full remaining term. As an illustrative example, on a £280,000 mortgage with twenty-five years remaining, a 0.2% green rate reduction produces around £9,500 in total mortgage interest saving. If £6,000 of improvements are financed at 8% over five years, the loan interest is around £1,300, bringing the total outlay to around £7,300. The net position is approximately £2,200 in favour — from the mortgage saving alone, before any energy bill saving is counted. The net position section of the calculator shows this comparison for your specific figures.
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The mortgage saving only applies from the point of remortgaging onto a green product, so timing matters.
Your existing mortgage rate is fixed by your current mortgage agreement regardless of any EPC improvement made during the fixed period. If your current deal has two years remaining, planning the improvements to complete in the year before that deal ends allows the new green rate to apply at the earliest opportunity. Some lenders offer mid-term product switches for newly qualifying properties, but this is not universal and may involve early repayment charges on the existing product, so it is worth confirming with your lender or broker.
Interactive tool
Green mortgage EPC saving calculator
See whether improving your EPC rating before remortgaging is financially worthwhile through the mortgage rate saving alone. Adjust the sliders to model your mortgage and improvement costs.
Your data stays private — nothing you enter is stored, transmitted, or accessible to anyone. All calculations run entirely in your browser.
Current and target EPC
Your mortgage
Illustrative. Actual premiums vary by lender and change over time. Check current green mortgage products before using a specific figure.
Some lenders offer a one-off cashback on completion instead of, or alongside, a rate reduction. Set to zero if modelling rate reduction only.
Loan details
About This Calculator
The rate differential
Why this is the most important variable and why you cannot rely on a published figure
The mortgage interest saving is approximately proportional to the rate differential: a 0.1% reduction saves roughly half as much as a 0.2% reduction. Green mortgage products exist at various lenders, but the rate differential varies by lender, product type, and current market conditions, and can change when a lender reprices or withdraws its green product range. The 0.20% default in this calculator is a commonly cited mid-range figure, but you should obtain current figures from a mortgage broker or directly from lenders before using a specific differential in any financial decision. Some lenders offer cashback on completion rather than a rate reduction: use the cashback slider to model this separately or alongside a rate discount. The rate reduction slider allows you to test a range of scenarios.
How the mortgage saving is calculated
Amortised interest over the remaining term
The calculator models the total interest paid on a repayment mortgage at the current rate versus the green mortgage rate over the full remaining term. The saving is the difference between the two total interest figures. This is more accurate than multiplying a flat annual saving by the number of years, because on a repayment mortgage the outstanding balance decreases over time, which means the interest saving in later years is smaller than in early years. The milestone table shows actual cumulative savings at regular intervals, calculated year by year from the amortising balances at each rate.
EPC threshold
What most lenders require and what reaching it involves
Most green mortgage products require EPC A or B. EPC C is accepted by some lenders but is less widely available and typically carries a smaller rate differential. Moving from EPC D to B typically requires a combination of two or three measures: loft insulation, cavity or solid wall insulation, and usually solar panels or a heat pump to push into the B band. Moving from D to C is achievable with insulation measures alone in many properties. The target EPC selector in this calculator allows you to model any target, with a note indicating whether it is likely to unlock mainstream green mortgage products.
The loan comparison
When paying higher loan interest to save lower mortgage interest makes sense
A home improvement loan for EPC works typically carries a higher rate than a mortgage. However, the loan is over a short term (typically three to seven years) while the mortgage saving applies over many years. As an illustration, on a £280,000 mortgage with twenty-five years remaining, a 0.2% green rate reduction saves approximately £9,500 in total mortgage interest. If £6,000 of EPC improvements are financed with a home improvement loan at 8% over five years, the loan interest is around £1,300. The net position — mortgage saving minus improvement cost minus loan interest — is approximately £2,200 in favour. The calculator makes this comparison visible for your specific figures.
How to Find Green Mortgage Products
Green mortgage products are available from a number of high street and specialist lenders, but availability and rates change frequently. Some lenders offer a direct rate reduction for EPC A or B properties, while others offer cashback on completion or fee-free additional borrowing for energy improvements. The most efficient way to identify current products and rates is through a whole-of-market mortgage broker, who can compare current green product ranges across lenders and identify the differential or cashback available for your specific property, loan-to-value ratio, and circumstances. A broker can also advise whether the EPC improvement you are planning is likely to qualify under a specific lender’s green product criteria, as requirements vary.
Timing matters for maximising the benefit. The mortgage saving only applies from the point of remortgaging onto a green product. If your current fixed rate deal has two years remaining, planning EPC improvements to complete in the year before that deal ends allows you to remortgage onto the green product at the earliest opportunity. Completing the improvements and obtaining a new EPC certificate before approaching lenders means you can demonstrate the qualifying rating during the application process. Some lenders accept a provisional EPC projection from an assessor rather than requiring the works to be completed, but this varies by lender and is worth confirming before planning the timeline.
This calculator is for home improvement loan planning only. Squared Money is an introducer for home improvement and secured loans, not a mortgage broker. We cannot advise on mortgage products or remortgage decisions. For mortgage advice, speak to a whole-of-market mortgage broker regulated by the FCA. The mortgage saving figures in this calculator are illustrative and should not be relied upon for mortgage decisions.
How to Use This Calculator
Set your current and target EPC
Select your current EPC rating from your most recent Energy Performance Certificate. Then select the target rating you expect to reach through planned improvements. Most green mortgage products require EPC B or A: the calculator flags whether your target is likely to qualify. Use the home energy upgrade sequencer to identify which improvements are most likely to achieve your target EPC band.
Enter your mortgage details
Use your current outstanding mortgage balance, interest rate, and remaining term from your most recent mortgage statement. For the rate differential, set the slider to the difference between your current rate and the best green mortgage rate currently available to you. If you do not have a specific figure yet, 0.15% to 0.20% is a typical range for EPC B properties.
Set the improvement cost and any cashback
Enter the total cost of the EPC improvements planned to reach your target band. Use quotes from installers if you have them, or use the illustrative cost figures from the home energy upgrade sequencer as a starting point. If the improvements are already planned for other reasons (comfort, running cost saving), set the cost to zero to see the pure mortgage saving without any improvement cost offset. If the green mortgage product offers cashback on completion, enter the cashback amount to see the combined benefit.
Toggle the loan section if financing the improvements
If you plan to finance the EPC improvements with a home improvement loan, toggle on the loan section and set the APR and term. The net position card updates to show the mortgage interest saving minus the loan interest cost, which is the true net financial benefit of the combined decision. A positive net position means the loan cost is justified by the mortgage saving it unlocks.
Related Tools and Guides
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Identifies which improvements are most likely to raise your EPC rating cost-effectively, in the right order. Use this to plan which measures to fund before the remortgage date.
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Energy efficiency loan payback calculator
Models when cumulative energy savings overtake total loan interest. Use this alongside the green mortgage calculator to see the combined return from energy saving and mortgage rate reduction.
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Home improvement loan calculator
Models different loan amounts, rates, and terms to estimate monthly repayments and total interest. Use this to refine the loan figures before entering them into the green mortgage calculator.
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Models your loan-to-value ratio and available equity. Relevant if you are considering a secured loan or second charge mortgage to fund EPC improvements rather than an unsecured product.
Guide
Home improvement loans for energy efficiency upgrades
Covers all the main energy efficiency improvements, their cost and saving profiles, and loan type guidance. Use this to understand which improvements are most cost-effective for reaching the target EPC band.
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EPC improvement before selling calculator
Models whether upgrading your EPC before selling adds enough to the sale price to justify the cost. Useful if you are considering EPC improvements for the sale value argument rather than the remortgage case.
Not sure what to look at next?
All of our home improvement loan guides and tools in one placeFrequently Asked Questions
Does every lender offer a green mortgage rate reduction?
No. Green mortgage products are available from a number of lenders but are not universal. The availability of green products, the EPC bands they require, and the type of incentive they offer varies significantly between lenders and changes as lenders update their product ranges. Some lenders offer a straightforward rate reduction for EPC A or B properties. Others offer cashback on completion rather than a rate reduction, and a growing number offer fee-free additional borrowing for energy efficiency works. A small number offer preferential rates from EPC C upward, though these are less common and typically carry a smaller differential than A or B products.
The practical implication is that the green mortgage saving in this calculator should be treated as a potential saving that depends on which lenders are offering suitable products at the time of your remortgage. A whole-of-market mortgage broker can identify current products and confirm which are available for your loan-to-value ratio, property type, and circumstances. Completing EPC improvements before starting the remortgage process means you can approach lenders with the qualifying rating already confirmed rather than relying on a projection.
Can I apply for a green mortgage on a buy-to-let property?
Some lenders offer green mortgage products on buy-to-let as well as residential mortgages, though the range of products is narrower and the EPC requirements may differ. For landlords, the Minimum Energy Efficiency Standards (MEES) regulations already require a minimum EPC of E for privately rented properties, and this threshold is set to rise to EPC C from October 2030 under current government plans. This means EPC improvement may be necessary for compliance regardless of any mortgage benefit. If the improvement needed to meet the incoming EPC C requirement also happens to take the property to EPC B, the green mortgage saving becomes an additional financial benefit of works that were already required.
For landlords with multiple properties, the combined mortgage saving across the portfolio from EPC improvements could be substantial. Each property’s saving depends on its individual outstanding balance, rate differential, and remaining term. This calculator models a single property: run the calculation separately for each property in the portfolio and sum the results for a portfolio-level view. Our guide to home improvement loans for rental properties covers the finance options for landlord EPC improvement works.
What EPC rating do I need to qualify for a green mortgage?
Most green mortgage products that offer a meaningful rate differential require EPC A or B. EPC B is the more commonly targeted band because EPC A requires near-perfect insulation and renewable generation, which is not achievable for most existing UK homes without very significant investment. EPC B is achievable for many properties through a combination of insulation improvements and a renewable energy source such as solar panels or a heat pump.
Some lenders accept EPC C for green or enhanced products, but the rate differential at C is typically smaller than at B, and fewer products are available. EPC D and below do not generally qualify for mainstream green mortgage products, though this may change as the market develops. When setting the target EPC in this calculator, the note below the EPC band selector indicates whether the selected target is likely to qualify for mainstream green mortgage products. EPC C is flagged as “check lender” because availability and differentials at that band are less consistent.
Does a new EPC certificate automatically change my mortgage rate?
No. A new EPC certificate only affects your mortgage rate if you actively apply to remortgage onto a green product. Your existing mortgage rate is fixed by your current mortgage agreement regardless of any EPC improvement made during the fixed period. The green mortgage rate becomes available at the point of remortgage, either at the end of a fixed rate period or through a product transfer with your current lender if they offer one.
Some lenders allow existing customers to switch to a green product mid-term if the property reaches a qualifying EPC band, but this is not universal and may involve early repayment charges on the existing product. It is worth checking with your lender whether a product transfer to a green rate is available without penalty if the EPC improvement is completed before your current deal ends. If the improvement is planned to coincide with a deal end date, the process is straightforward: complete the works, obtain a new EPC certificate, and remortgage onto a green product at the point of renewal.
Squaring Up
The green mortgage saving is an often-overlooked financial benefit of EPC improvements that sits alongside the energy bill saving and the capital value argument. On a large mortgage with many years remaining, even a modest rate differential of 0.15% to 0.2% produces a total interest saving that can exceed the cost of the improvements, particularly when those improvements are also generating an energy bill saving from day one. The combined case is often stronger than either calculation in isolation.
The most important practical step is finding out what green mortgage rate you can actually access before spending on improvements. Completing works to reach EPC B and then discovering that no competitive green product is available at your loan-to-value ratio would undermine the financial case. Speak to a whole-of-market mortgage broker about current green product availability before planning the improvement timeline. This calculator models the potential saving: confirming the actual saving available to you requires a current market search.
Continue your research
Guides, calculators, and comparators covering every aspect of home improvement finance Explore guides and toolsUpdate log: July 2026
What changed in this update
Calculator accuracy improvements: the milestone table now uses actual year-by-year cumulative savings from amortising balances at each rate, replacing the previous average-based approach which understated early-year savings. Illustrative worked examples updated to reflect current calculator output. Rate differential range updated to 0.10%–0.25% based on current market data.
New feature: cashback slider added to model lenders that offer a one-off cashback on completion rather than, or alongside, a rate reduction. This reflects the growing number of green mortgage products structured as cashback incentives.
Accessibility and usability: contrast ratios improved across the tool interface, ARIA labels added to all interactive controls and result areas, and the MEES context in the buy-to-let FAQ expanded to include the confirmed EPC C target from October 2030.
This tool is for illustrative purposes only and does not constitute financial or mortgage advice. Squared Money is an introducer for home improvement and secured loans, not a mortgage broker or lender. All mortgage saving figures are illustrative estimates based on the inputs provided and will differ from actual savings, which depend on the specific green mortgage products available to you, your lender’s eligibility criteria, your loan-to-value ratio, and market conditions at the time of remortgage. Green mortgage product availability, EPC requirements, and rate differentials change over time. For mortgage advice, speak to a whole-of-market mortgage broker authorised and regulated by the FCA. Your home may be at risk if you do not keep up repayments on a secured loan or mortgage.
