Thermal curtain heating savings: how much really?
A high-density thermal curtain (500 g/m² and more) reduces heat loss through windows by 20 to 30%, which translates into estimated heating savings of 60 to 150 euros per year for a 60 to 80 m² dwelling with 5 windows (electric heating at €0.22/kWh). The return on investment is achieved in 2 to 4 years, compared to 10 to 30 years for window replacement.
This guide quantifies real savings based on your type of glazing, your heating method, and your home's glazed surface area. No vague promises: concrete calculations based on ADEME data and measured performance.
How much do your windows cost in heating each year?
According to ADEME, windows account for 10 to 15% of a dwelling's heat loss. For an average French household that spends 1,600 euros per year on heating (source: Observatoire de l'énergie, 2024), this represents 160 to 240 euros of heat lost through windows each year.
This cost varies according to the type of glazing:
| Glazing type | Ug coefficient | Share of window heat loss | Estimated annual cost (70 m² dwelling) |
|---|---|---|---|
| Single glazing | 5.8 W/m².K | 20-25% | 320-400 €/year |
| Old double glazing (before 2000) | 2.8-3.0 W/m².K | 12-18% | 190-290 €/year |
| Recent double glazing | 1.1-1.4 W/m².K | 8-12% | 130-190 €/year |
Even with recent double glazing, your windows cost 130 to 190 euros in heating per year. This is the thermal weak point of your home: an insulated wall has a U-value of 0.2 to 0.5 W/m².K, which is 3 to 7 times less heat loss than the best double glazing.
How much does a thermal curtain save?
A high-density thermal curtain (500 g/m² and more) reduces heat loss through windows by 20 to 30%. By applying this percentage to the annual cost of heat loss through windows:
| Situation | Window cost/year | Curtain reduction | Annual savings |
|---|---|---|---|
| Single glazing, 5 windows | 320-400 € | 20-30% | 65-120 €/year |
| Old double glazing, 5 windows | 190-290 € | 20-30% | 40-85 €/year |
| Recent double glazing, 5 windows | 130-190 € | 20-30% | 25-55 €/year |
Overall range: 25 to 120 euros in savings per year depending on the glazing and heating method. Savings are higher with electric heating (the most expensive per kWh) than with gas or a heat pump.
These figures are estimates based on ADEME data and the measured performance of Kurtens curtains (up to 7°C gain*). Actual savings vary depending on the region, the severity of winter, heating habits, and the condition of window seals.
Return on investment
The calculation is simple: purchase cost of curtains divided by annual savings.
| Investment | Cost | Savings/year | Return on investment |
|---|---|---|---|
| 5 custom-made Kurtens thermal curtains | 400-1,300 € | 25-120 € | 3-10 years |
| 5 double-glazed windows (replacement) | 3,000-10,000 € | 65-250 € | 12-40 years |
| Insulating film (5 windows, redone annually) | 25-75 €/year | 15-50 € | Never (cost > savings) |
The thermal curtain offers the best return on investment of the three solutions. Window replacement is more effective in pure insulation but pays for itself in 12 to 40 years (often beyond the lifespan of the glazing). Insulating film costs almost as much each year as it saves.
Unquantifiable bonus: the Kurtens thermal curtain also provides 100% blackout* (savings on blinds and shutters) and sound attenuation of 22 dB* (daily living comfort). These benefits do not translate into euros on the heating bill but concretely improve comfort.
Factors that increase or decrease savings
Factors that increase savings
- Single glazing: heat loss is maximal, the curtain's gain is proportionally greater.
- Electric heating: the most expensive kWh (€0.22/kWh at basic rate 2026). Each kWh saved is worth more than with gas (€0.10/kWh) or a heat pump (€0.07-0.10/kWh effective).
- Large glazed surfaces: a 4 m² bay window loses 3 to 4 times more heat than a 1 m² window. A curtain on a large bay generates proportionally greater savings.
- Cold region: the more severe and long the winter, the more the heating runs, the higher the savings. A home in Lille saves more than a home in Nice.
- Curtain closed at night: heat loss is maximal at night (lowest outside temperature). Systematically closing the curtain in the evening and reopening it in the morning maximizes savings.
Factors that reduce savings
- High-performance double glazing: basic heat loss is already low, the marginal gain from the curtain is less.
- Poorly sized curtain: a curtain that is too narrow or too short (without an overhang of 15-20 cm on each side) loses 30 to 40% of its effectiveness. Lateral leaks let in cold air and reduce savings.
- Shutters closed at night: if you already have shutters that you close every evening, adding a curtain is a complement (reduced gain) and not a primary solution.
Comparison with other heating saving solutions
| Solution | Investment | Savings/year | ROI | Work |
|---|---|---|---|---|
| Custom thermal curtains (5 windows) | 400-1,300 € | 25-120 € | 3-10 years | No |
| Window seal replacement | 25-50 € | 10-30 € | 1-2 years | No |
| Radiator reflectors (5 radiators) | 50-125 € | 15-40 € | 2-4 years | No |
| Programmable thermostat | 50-300 € | 50-150 € | 1-3 years | No |
| Attic insulation | 2,000-5,000 € | 150-400 € | 5-15 years | Yes |
| Double glazing window replacement | 3,000-10,000 € | 65-250 € | 12-40 years | Yes |
The most effective combination without major work: new seals + thermal curtains + radiator reflectors. Total investment: 475 to 1,475 euros. Cumulative savings: 50 to 190 euros per year. Return on investment: 3 to 8 years. No professionals, no authorization, no modification of the dwelling.
The thermal curtain: an investment, not an expense
A Kurtens thermal curtain lasts 10 to 15 years. Over this period, cumulative savings far exceed the initial investment:
- Single glazing scenario: investment 400 to 1,300 euros, savings 65-120 euros/year, cumulative savings over 10 years: 650 to 1,200 euros. The curtain pays for itself and generates a net profit.
- Old double glazing scenario: investment 400 to 1,300 euros, savings 40-85 euros/year, cumulative over 10 years: 400 to 850 euros. The curtain pays for itself or approaches break-even.
And unlike insulating film (to be redone annually) or window replacement (not portable), the Kurtens curtain is portable. It moves with you if you relocate. The investment is not lost if you change dwellings.
Discover our custom-made anti-cold thermal curtains: 620 g/m², up to 7°C thermal gain*, 100% blackout*, 22 dB sound attenuation*. 7 colors, manufactured to exact dimensions, free delivery in 2 to 3 weeks. To understand the science behind textile insulation, consult our article how a thermal curtain works. To compare with double glazing, consult thermal curtain vs. double glazing.
*Data from tests conducted under optimal conditions.
Frequently asked questions
How much can you save with a thermal curtain?
For a 60-80 m² dwelling with 5 windows and electric heating: 25 to 120 euros per year depending on the type of glazing. Single glazing: 65-120 euros/year. Old double glazing: 40-85 euros/year. Recent double glazing: 25-55 euros/year. Savings are lower with gas or a heat pump because the kWh costs less.
How long does it take for a thermal curtain to pay for itself?
The return on investment is 3 to 10 years depending on the type of glazing and heating method. With single glazing and electric heating (most favorable case): 3-5 years. With recent double glazing and a heat pump (least favorable case): 8-10 years. The curtain lasts 10 to 15 years, so it generates a net profit over its lifespan in most cases.
Is a thermal curtain more cost-effective than double glazing?
In terms of return on investment, yes. The curtain pays for itself in 3-10 years (investment 400-1,300 euros for 5 windows). Double glazing pays for itself in 12-40 years (investment 3,000-10,000 euros). Double glazing offers better pure thermal performance, but the curtain is 5 to 10 times cheaper and also provides blackout and sound insulation.
Are the savings the same with gas as with electricity?
No. The kWh gain is the same, but the kWh does not cost the same. Electric heating: €0.22/kWh (maximum savings). Gas: ~€0.10/kWh (savings divided by 2). Heat pump: €0.07-0.10/kWh effective (savings divided by 2-3). Savings in euros are about 2 times higher with electric heating than with gas.
Should the thermal curtain be closed permanently to save money?
No. The optimal strategy: keep the curtain open during the day to benefit from free solar gain (the sun heats the room for free), close the curtain as soon as the sun sets to trap accumulated heat and block nocturnal heat loss. Losses are maximal at night (lowest outside temperature). Systematically closing the curtain in the evening generates the most savings.
Are there financial aids for thermal curtains?
No. Public aids (MaPrimeRénov', CEE, eco-PTZ) only concern structural energy renovation work (window replacement, wall insulation, boiler replacement). Thermal curtains are not eligible because they are reversible and not structural. But their cost (80-350 euros per window) is already 5 to 10 times lower than double glazing before aid.
Do heating savings justify custom-made curtains?
Yes. A poorly sized curtain (without a 15-20 cm side overhang) loses 30 to 40% of its thermal efficiency. For savings of 80 euros/year, a 30% loss represents 24 euros/year in missed gains, or 240 euros over 10 years. The extra cost of custom-made compared to a standard size is generally less than this loss. Custom-made also pays for itself through performance.
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