Advanced options
The honest numbers: whole-house single-to-double savings are ~GBP 140-195/yr (Energy Saving Trust): real but slow against a GBP 5-8k install. People fit double glazing for the OTHER returns: warmth and no draughts, halved outside noise, no condensation streaming down the glass, security, and the EPC/valuation bump when selling. If payback is the goal, draught-proofing and loft insulation repay in a fraction of the time: do those first.
What The Double Glazing Savings Calculator Works Out
- Energy saving: the number of windows multiplied by the saving per window. The Energy Saving Trust puts whole-house single-to-double savings at GBP 140 to GBP 195 a year for a typical home, about GBP 14 per window; upgrading tired old double glazing to modern A-rated units saves around GBP 5 per window.
- Project cost: windows x the fitted price per window. Installations run GBP 500 to GBP 800 per window fitted, so a ten-window house is GBP 5,000 to GBP 8,000.
- Payback on bills alone: the project cost divided by the yearly saving. It usually stretches past three decades and beyond the sealed units' own working life, which is why people fit double glazing for the other returns: warmth, halved street noise, no condensation rivers, security and the EPC and valuation bump at sale.
- Custom saving per window (advanced): enter your own figure, for example from an EPC recommendation or a quote, when the presets do not match your house or heating fuel. Electric-heated homes save roughly three times as much per window as gas-heated ones.
- Future energy price change (advanced): compounds the saving each year at the rate you set, so you can test what rising or falling prices do to the lifetime figure.
- Sealed unit life (advanced): modern units are typically guaranteed for 10 years and last 20 to 35 before seals fail and misting starts. The lifetime card adds up every year's saving and compares it with the cost.
- Discount or grant (advanced): knocks any negotiated discount or scheme contribution off the project cost. Multiple quotes with the theatrical first price declined on principle is the buying folklore; the discount-for-signing-today is the industry's oldest costume.
- Net annual cost of ownership (advanced): the project cost spread over the units' life minus the yearly saving, which is the honest price of the comfort, noise and condensation benefits each year.
- Secondary glazing instead (advanced): a second pane fitted inside the existing window, the conservation-area and listed-building staple, typically GBP 100 to GBP 300 per window and capturing around 60% of the thermal gain and most of the acoustic gain. Draught-proofing and loft top-ups repay faster than either and belong first in the plan.
Savings basis: Energy Saving Trust.