Window energy ratings now use A++ to E scale. A-rated windows save £100-£200 annually compared to E-rated single glazing.
Window Energy Ratings
| Rating | U-Value | Typical Window | Annual Heating Saving vs Single |
|---|---|---|---|
| A++ | <0.5 | Triple glazing + low-E | £200-£300 |
| A+ | 0.5-0.75 | Triple glazing + low-E | £180-£250 |
| A | 0.75-1.0 | Double glazing + low-E | £140-£180 |
| B | 1.0-1.25 | Double glazing | £100-£140 |
| C | 1.25-1.6 | Older double | £60-£100 |
| D | 1.6-2.0 | Very old double | £20-£60 |
| E | >2.0 | Single glazing | £0 |
U-Value Explained
U-value measures heat loss. Lower is better. A U-value of 1.0 means 1 watt per square metre loses heat for every 1°C temperature difference.
Single glazing: U-value 5.0
Double glazing: U-value 2.0
A-rated double: U-value 0.8
Triple Glazing vs Double
Double Glazing: A-rating achievable, cost £200-£400/window, saves £140-£180/year
Triple Glazing: A++ rating, cost £400-£700/window, saves £200-£300/year
Payback: Triple glazing costs £100-£300 extra but saves only £60-£120 annually. Payback 15-30 years (not always justified).
Key Technologies for A-Rated Windows
Low-E Coating: Invisible metallic coating reflects heat back into room. Adds £30-£60/window. Essential for A-rating.
Argon or Krypton Gas Fill: Non-toxic gas between panes reduces heat loss. Standard in A-rated windows.
Warm Edge Spacer Bars: Plastic spacers instead of aluminum reduce heat loss at edges. Improves rating by 0.1-0.2.
Annual Savings Examples
Replacing single glazing with A-rated double: £140-£180 annual saving
Replacing old double with A-rated: £80-£120 annual saving
Typical 10-window house replacement cost: £2,500-£4,000 (with installation)
Payback period: 15-25 years
Get Window Quotes
Get quotes for A-rated energy-efficient windows in your area.