If your energy bills crept up again this winter, your windows might be the easiest place to claw money back. Modern glazing does far more than stop a draught, it insulates your home, reduces condensation, and makes rooms feel calmer and warmer. This guide explains what to look for in 2026, what you can realistically save, how to spot failing older double glazing, and how to choose frames that suit your home and budget.

Window energy ratings, explained simply

In the UK, the BFRC window energy rating works a bit like appliance labels. You will see a coloured band from A++ down to E. The higher the grade, the more efficient the whole window is as a system, including frame, glass, spacers and gas fill. For most homes, aim for A rated or better. This balances strong thermal performance with sensible cost.

Alongside the letter band, you will often see a figure called the U‑value. This measures how much heat passes through the window. Lower is better. Good double glazing today sits around 1.2 to 1.4 W/m²K for the whole window. Triple glazing can drop closer to 0.8 to 1.0 W/m²K, which suits exposed or very cold locations, or when you are chasing the best possible EPC uplift.

The glass technology that actually saves energy

• Low‑E coatings: A near‑invisible metal oxide layer on the inner pane reflects heat back into your room while letting sunlight in. You get the warmth without the heat escaping.
• Argon gas fill: Argon is denser than air, so it slows heat transfer between the panes. It is safe, odourless, and standard on most quality units. Krypton is used in some triples, but argon offers the best value for most homes.
• Warm‑edge spacers: These are the strips that separate the panes around the perimeter. Traditional aluminium spacers act like a cold bridge. Modern warm‑edge spacers use insulating materials to reduce heat loss and cut down on condensation around the edges of the glass.
• Triple glazing: Adding a third pane improves insulation and noise reduction. The trade off is cost and weight. For busy roads, exposed plots and high performance refurbishments, it is a smart choice. For many suburban homes, a top end A rated double unit with low‑E, argon and warm‑edge spacers delivers excellent value.

Which frames are most energy efficient?

• uPVC: The best value thermal performer for most homes. Multi‑chambered profiles trap air and reduce heat loss. Modern uPVC looks smarter than older styles and needs minimal upkeep. If you want efficiency on a sensible budget, uPVC is hard to beat.
• Aluminium: Today’s aluminium frames include a thermal break, a non conductive section that stops heat crossing from inside to out. With this technology and quality glazing, aluminium can meet A ratings while giving you slim sightlines and a sleek, contemporary look. Great for larger panes and bays.
• Composite (aluminium clad timber or hybrid systems): These combine a timber core for natural insulation with an aluminium external cap for durability. Thermal performance is strong, aesthetics are premium, and prices are higher. If you want a timber feel without timber maintenance, composites are worth a look.

So, what type of windows are most energy efficient? On a pure numbers basis, a well specified composite or triple glazed aluminium system can top the charts, but for most UK homes the sweet spot is A rated uPVC or thermally broken aluminium with high performance double glazing. It is about the whole window system and the installation quality, not just the material label.

How to tell if a window is energy efficient

• Look for the BFRC label showing A to A++ with the U‑value listed.
• Ask for the glass spec. You want a soft‑coat low‑E pane, argon fill, and warm‑edge spacers as standard.
• Check the frame system. Is it multi‑chambered uPVC or thermally broken aluminium? Are there quality seals and compression gaskets?
• Ask about installation. Even the best window underperforms if gaps are poorly sealed. Professional fitting, airtight tapes or appropriate sealant, and proper packers make a real difference.

Signs your 20 year old double glazing needs replacing

Is it worth replacing 20 year old double glazing? Often, yes. Glass and frame tech has moved on a long way since the early 2000s. Tell tale signs include:

• Misted glass between the panes, the seal has failed and the unit has lost its insulating gas.
• Persistent draughts around sashes or beads, even when shut.
• Stiff, warped or cracked frames; discoloured uPVC that is brittle.
• Cold spots and condensation at the edges of the glass.
• Rising energy bills despite similar usage.

If you have two or three of these symptoms, you will feel a clear comfort improvement from replacement, and your heating system will not need to work as hard.

What makes a window not energy efficient?

• No low‑E coating or gas fill, just basic float glass in older units.
• Metal spacers that act like a heat highway to the outdoors.
• Single glazing or early double glazing with wide aluminium frames and poor seals.
• Bad installation with gaps, minimal foam, and failing trims.
• Worn seals and failed gaskets that let warm air escape.

Typical UK prices in 2026

Every home is different, but realistic ballpark figures per standard casement window supplied and fitted are:

• uPVC A rated double glazing: £450 to £800 per window for common sizes.
• Aluminium thermally broken double glazing: £800 to £1,200 per window.
• Composite or triple glazing: £1,100 to £1,600 per window depending on brand and size.

Bays, shapes, sash styles, acoustic glass, integral blinds, and conservation details will push costs higher. Whole house projects usually attract better per unit pricing.

What you can save on energy bills

Savings vary with house type, number of windows and your current glazing. As broad guidance for a gas heated UK home replacing 15 to 20 old double glazed units with modern A rated windows:

• Annual bill savings: roughly £150 to £300 on typical 2026 tariffs for a semi‑detached home, more if your existing units are failing badly.
• Comfort gains: fewer draughts, warmer surface temperatures on glass, reduced condensation, and better sound insulation.
• EPC uplift: improved window performance can help move a home to a higher EPC band, useful for resale and for landlords.

Average cost of an energy efficient window

If you want a one line figure, the average cost of an energy efficient window in 2026, across materials and sizes, lands around £750 to £1,000 installed. Most straightforward uPVC jobs come in under that average, while aluminium and triples sit above it. Always compare itemised quotes like for like, including glass spec, hardware, trims and making good.

Ready for spring? Why book a winter survey

Winter shows up draughts and cold spots clearly, so it is the best time for a survey. Lead times are also calmer before spring. If you book a free survey now, you can get your installation lined up for the milder months, with less disruption and faster fitting days.

At Clearview 2000, you get an honest, no pressure quote, tidy installations, and a 10 year guarantee on products and workmanship where applicable. Our surveyor will talk you through BFRC ratings, U‑values and the right glass spec for each room, so you choose with confidence. We protect your floors, keep sites neat, and our fitters clean up at the end of each day.

If you are comparing options for energy efficient windows, you can also explore our guide to energy efficient windows for more detail. We handle everything from first measure to aftercare, and we are local to Hertfordshire. When you are ready, get in touch to book your free survey and be spring ready.