Close your curtains at 19:45: the spring routine that keeps heat in and cuts your energy bill

As spring arrives, many people turn the heating down a notch but keep it running. There’s a surprisingly large saving to be had from a simple habit: drawing your curtains at the right time helps trap warmth indoors and can noticeably reduce heating costs - no gadgets required, just good timing and the right fabric.

The curtain trick: what’s really going on

The principle is straightforward. During the day, sunshine warms your home for free. Windows that receive direct sun can act a bit like a magnifying glass, letting a lot of energy into the room. Once it gets dark outside, that benefit flips: the same glass area becomes a route for heat to escape back outdoors.

If you close the curtains as dusk falls, you create an extra layer of warmth in front of the window - like a thin, flexible form of insulation.

In March, that “switch-over” point is often around 19:45. Around then, outdoor temperatures typically start dropping, even though the warmth built up indoors during the day is still useful. If curtains and blinds stay open, much of that stored heat is lost and your heating has to make up the difference.

Why spring is the key moment

March is a sweet spot: days get longer, the sun sits higher, and it can warm rooms more effectively. Homes with south- or west-facing windows benefit most. At the same time, the heating season isn’t finished - nights can still be chilly, and living spaces can cool down quickly.

If you deliberately “lock in” the day’s warmth, you can often drop the heating by one or two settings. The difference is usually bigger in older, poorly insulated properties than in modern buildings, but even well-insulated flats can benefit over several weeks and months.

How much money can you actually save with curtains?

Exact savings depend on plenty of variables - window quality, insulation standard, heating system and energy prices. Even so, energy advisers consistently report that purposefully closing curtains and blinds can substantially reduce heat loss through windows.

• Windows are often the biggest weak point in a building’s outer shell.
• Glass transfers cold and heat faster than an insulated wall.
• The larger the window area, the more energy you can lose without a barrier.

A useful rule of thumb: if better heat retention lets you set the heating just 1°C lower in the evening, the average heating energy demand falls by around 6%. Over a year, that can add up quickly for a typical household - often mid double-digit to low triple-digit sums - purely from changing your evening routine.

Thermal curtains: what they can (and can’t) do

Standard decorative curtains can already help, provided they cover as much of the window area as possible. The effect becomes much stronger with thermal curtains designed specifically for insulation, usually with a thick, multi-layer weave or an insulating backing.

Thermal curtains act like an additional soft insulating layer in front of the glass - keeping warm air in and blocking cold draughts.

Good-quality options can cost around £85–£100 per pair (often quoted at roughly €100). That may feel like a noticeable outlay, but it can make more sense over time: if you heat a little less for several years, you can often recoup the purchase price.

Thermal curtains: what to look for when buying

• Fabric thickness: the thicker the material, the better the insulating effect.
• Backing: look for a thermal coating or a lining such as fleece, felt, or similar.
• Length: ideally down to just above the floor so cold air can’t flow in underneath.
• Width: aim for at least twice the window width to avoid gaps.
• Hanging height: mount as close above the window as possible so heat doesn’t escape at the top.

Making the 19:45 trick work in real life

This is mostly about habit. Once you start closing the curtains at a set time each evening, it quickly becomes automatic. These steps make it easier to stick with:

1. Check the time: when does it actually get dark where you live in March? A practical guide is about 19:30 to 20:00.
2. Set a reminder: use a phone alarm for the first two weeks.
3. Fix the sequence: air the room briefly with windows wide open, then shut the windows, then draw the curtains.
4. Adjust the heating: after a few days, test whether the room stays stable if you turn the heating down slightly.

After just a handful of evenings, many people notice the room stays comfortably warm for longer while outdoor temperatures fall.

A helpful extra step is to make it “frictionless”: keep curtain pulls accessible, and if multiple people are at home, agree who closes which rooms so it becomes a shared routine rather than an afterthought.

Summer bonus: a heat shield instead of a heat store

Thermal curtains aren’t just for winter. In summer, the effect works in reverse: ventilate briefly in the morning while the air outside is still cool, then close the windows and keep curtains or blinds drawn during the day. That reduces how much heat gets in, helping rooms stay tolerable for longer.

This is especially useful in top-floor flats and rooms with large areas of glazing, where peak indoor temperatures can be noticeably reduced. If you normally reach straight for a portable air conditioner on hot days, smart curtain management can often cut how much you need it - saving electricity in the process.

Curtains are only one piece - these combinations deliver even more

The curtain trick is most effective when paired with other simple measures. For example:

Measure	Benefit in winter	Benefit in summer
Close roller shutters at night	Further reduces heat loss alongside curtains	Blocks direct sun
Add sealing strips to window frames	Less draught, more even indoor comfort	Helps keep hot outdoor air from flowing in
Put a rug on cold floors	Feet stay warmer, heating feels less necessary	More comfortable underfoot, less temperature awareness

Each action contributes only part of the result on its own, but together they can noticeably improve comfort while lowering energy costs.

Common mistakes that ruin the savings

Some habits reduce how well thermal curtains work, including:

• Hiding the radiator behind a fully closed curtain - the heat then struggles to circulate into the room.
• Styling curtains to the side so large areas of glass remain exposed.
• Leaving a window on the latch while the curtains are closed - warm indoor air is channelled straight outside.
• Choosing short curtains that only reach the window sill.

The best setup is usually one where the curtain ends just above the radiator, or is mounted so warm air can still flow into the room. In rented homes where the radiator position is awkward, special rails, poles or brackets can help hold the fabric slightly away from the heater.

Extra consideration: warmth retention vs fresh air

Holding on to heat shouldn’t mean sacrificing ventilation. If you’re prone to condensation, avoid keeping windows slightly open behind closed curtains, and instead ventilate briefly and properly earlier in the evening (or use background ventilation where available). Keeping the window area dry and allowing a little airflow where appropriate can help prevent damp and mould without undermining the overall “close at dusk” routine.

Why this simple step is so appealing right now

Many households are still feeling the impact of higher energy prices. Major upgrades like new windows or external wall insulation are costly and can’t be done overnight. By comparison, using curtains deliberately can feel almost too basic - yet it works immediately, takes little effort, and can be done in any home, whether you rent or own.

Once you understand the principle, you often start looking at windows differently: what do you do in the morning and in the evening? When do you invite light and warmth in, and when do you block them? Thermal curtains and a fixed time such as 19:45 are simply tools - the real lever is the everyday routine.