One question we get asked a lot by homeowners across Portsmouth and the surrounding areas is whether paying extra for A rated windows actually makes financial sense, or if it’s simply a nice to have specification that sounds good on paper. As installers who work with energy ratings every day, we think it’s worth giving you a straight answer based on how these ratings work, what they actually represent, and what kind of savings you can realistically expect on your energy bills.
Do A Rated Windows Pay Back in Energy Savings
- BFRC ratings range from A++ down to E, based on U-value, solar gain, and air leakage combined
- Higher rated windows lose less heat, reducing the workload on your heating system
- Typical savings depend heavily on your existing windows, home size, and heating habits
- Upgrading from old single glazing to A rated double glazing offers the biggest savings
- Upgrading from older double glazing to A rated units offers smaller but still worthwhile savings
- Payback periods vary widely, often ranging from several years to over a decade
- Energy savings are one benefit alongside comfort, condensation reduction, and noise insulation
- The “right” rating depends on your property, budget, and how long you plan to stay in your home
What BFRC Ratings Actually Measure
The British Fenestration Rating Council operates the Window Energy Rating scheme, which grades windows on a scale from A++ at the top down to E. This rating isn’t based on a single figure, but combines three separate factors into one overall grade, the U-value of the window, the solar factor (how much heat from sunlight passes through the glass), and air leakage around the frame and sash.
This combined approach is useful because it reflects how a window performs as a whole, rather than focusing purely on insulation. A window could theoretically have a very low U value but still lose marks if it allows excessive air leakage around poorly sealed joints, so the BFRC rating gives a more rounded picture of real world performance.
For context, under current UK Building Regulations, replacement windows must achieve a whole window U-value of 1.4 W/m²K or better, which typically corresponds to a B rating or thereabouts. A rated windows generally sit at U-values around 1.2 W/m²K or lower, with A++ representing the most efficient products currently available, often achieving U-values below 1.0 W/m²K through features like krypton gas fill or vacuum glazing.
Where the Real Savings Come From
The honest answer to whether A rated windows pay back in energy savings depends enormously on what you’re upgrading from. This is the single biggest factor, and it’s something we always discuss with homeowners before they commit to a particular specification.
If you’re currently living with original single glazed windows, which still exist in a fair number of older properties around Portsmouth, particularly in upper floor sash windows that haven’t been replaced, the jump to A rated double glazing represents a substantial improvement. Single glazing typically has a U-value around 4.8 to 5.7 W/m²K, compared to around 1.0 to 1.2 W/m²K for A rated double glazing. That’s a difference of roughly four to five times the heat loss, and the impact on comfort and heating costs from this kind of upgrade is usually very noticeable.
If you’re upgrading from older double glazing, say units installed in the 1990s or early 2000s with a U-value around 2.0 to 2.8 W/m²K, to modern A rated windows around 1.0 to 1.2 W/m²K, the improvement is real but proportionally smaller. You’re still reducing heat loss through the windows by perhaps 40 to 50 percent, but because the starting point was already reasonably insulating compared to single glazing, the absolute savings on your energy bill will be more modest.
Calculating Realistic Payback Periods
Working out an exact payback period for window upgrades is genuinely difficult, because it depends on so many variables specific to your home and how you use it. However, we can talk through the factors that influence this calculation so you have a realistic picture rather than relying on marketing figures that often assume best case scenarios.
The size of your property and the proportion of external wall taken up by windows matters significantly. A property with large bay windows or extensive glazing will see proportionally more benefit from window upgrades than a property with small window openings, simply because windows represent a larger share of the total heat loss from the building.
Your heating habits and how much of the property you heat, and to what temperature, also affects the calculation. A home that’s heated to 21 degrees throughout for long hours each day will see more absolute savings from reduced heat loss than a home that’s heated more sparingly, simply because there’s more heat available to be retained.
The cost of your heating fuel matters too. With energy prices having risen significantly in recent years, the financial value of each unit of heat retained is higher than it would have been a decade ago, which improves the payback calculation for any insulation upgrade, windows included.
As a general guide, based on typical UK housing stock and average energy costs, upgrading from single glazing to A rated double glazing across a whole house can often show payback periods in the range of 10 to 20 years when considered purely on energy savings alone, though this varies considerably between properties. Upgrading from older double glazing to A rated units tends to show longer payback periods on energy savings alone, often extending beyond the typical lifespan many homeowners plan to stay in a property.
Why Payback Isn’t the Whole Picture
We’d always encourage homeowners to think about window upgrades as more than a pure energy saving calculation, because there are other benefits that don’t show up directly on an energy bill but genuinely affect day to day living.
Comfort is probably the most immediately noticeable change, particularly the reduction in cold spots near windows and draughts around frames and seals. Even if the pounds and pence savings on heating take years to become apparent, the comfort improvement is usually felt within the first cold spell after installation.
Condensation reduction is another significant factor, particularly relevant in bathrooms, kitchens, and bedrooms where moisture levels are higher. Improved U-values and warm edge spacer bars reduce the cold surfaces where condensation typically forms, which can help with damp and mould issues that older, less efficient windows sometimes contribute to.
Noise insulation tends to improve with higher specification glazing too, which is something we hear about a lot from homeowners on busier roads around Portsmouth, where the difference in external noise levels after upgrading windows is often more immediately appreciated than the energy savings.
There’s also the simple fact that if your existing windows are reaching the end of their functional life, with failing seals, difficult opening mechanisms, or visible deterioration, replacement becomes necessary regardless of the energy calculation. In that scenario, the question isn’t really whether to replace, but what specification to choose for the replacement, and the additional cost of specifying A rated units over a lower rating is often relatively small in the context of the overall project cost.
Choosing the Right Rating for Your Situation
Given all of this, our advice to homeowners is generally that if you’re replacing windows anyway, whether due to age, condition, or a renovation project, specifying A rated or higher windows makes sense in almost all cases. The additional cost over a B rated specification is typically modest compared to the overall cost of the windows and installation, and you’ll benefit from the improved comfort and reduced energy use for the full lifespan of the windows, which is often 20 years or more.
Where the calculation becomes more nuanced is if you’re considering replacing windows purely for energy savings, with no other driving factor such as failing frames or a renovation project already underway. In that scenario, it’s worth having an honest conversation about your specific property, your current windows, and your heating patterns before committing to the expense, as there may be other improvements, such as loft insulation or draught proofing, that offer quicker returns for a lower outlay.
If you do decide to proceed, choosing A rated uPVC windows with features like Low E coatings, argon or krypton gas fill, and warm edge spacer bars ensures you’re getting genuine performance benefits that will continue to deliver value throughout the life of the windows, even if the precise payback period is difficult to pin down to an exact number of years.
Get Honest Advice from BJH Windows & Conservatories
At BJH Windows & Conservatories, we believe in giving homeowners across Portsmouth and the surrounding areas honest, straightforward advice about window specifications, including what level of investment makes sense for your particular property and circumstances. We supply and install A rated and BFRC certified uPVC windows as standard, and we’re happy to talk through the realistic benefits for your home rather than relying on generic figures. Contact us today for a no obligation conversation about your replacement windows.
About the Author
Oscar Hamilton
Trainee ManagerI am the third-generation member of the BJH Windows family! I have a deep-rooted passion for the business. I achieved a First-Class degree in Business Management and Leadership from the University of the West of England. Having worked summers at BJH since my childhood, I have hands-on experience in the industry, even starting as a fitter’s mate. I am a fully qualified FENSA surveyor, combining my academic knowledge and practical expertise to deliver exceptional service, ensuring the family legacy of quality and customer care continues.
