Close Curtains at 19:45 to Cut Heating Costs

Between afternoon spring sunshine and cooler evening hours, many homes face a costly gap: rooms lose heat more quickly than we would like, while energy prices remain high. A straightforward routine from around 19:45, recommended by energy experts in the UK, can also help households elsewhere cut heating bills – without any new technology, simply by drawing the curtains.

Why curtains should be closed from around 19:45

Around the middle of March, daily routines change as daylight lasts noticeably longer and afternoon sun provides more warmth to living rooms and bedrooms. From an energy perspective, that heat is worth retaining rather than allowing it to escape straight back through the windows.

“Anyone who consistently closes their curtains from around 19:45 keeps the warmth stored during the day in the home for longer, reducing the demand on the heating system.”

The reason is straightforward: even in modern homes, windows remain a weak point in the building envelope. Glass transfers heat more readily than an insulated wall, and panes cool considerably overnight. Once the sun has gone down, the process reverses, with the window releasing indoor heat to the colder outside air.

From mid-March, sunset in many areas falls at or shortly before 19:45. This makes the time a useful rule of thumb: until then, sunlight still contributes a little to warming the home, but afterwards heat loss through the glass becomes the dominant effect. Closing the curtains at that point slows the loss.

The physics: curtains as a “second window pane”

Curtains are not a replacement for insulation, but they form an additional thin layer between the room air and the window glass. This creates a type of air pocket that slows down heat transfer.

“Dense fabric in front of a window pane reduces the flow of heat to the outside – a small change with a clearly noticeable effect on the indoor climate.”

The colder the night, the more apparent the difference becomes. Rooms where curtains are drawn early in the evening stay comfortable for longer, whereas unprotected window areas can turn into “cold traps”. Anyone who then turns up the thermostat pays for that effect directly through their energy bill.

Which curtains make a genuine difference

Not all fabrics perform equally well. Thin, decorative curtains are primarily intended for appearance. For a noticeable result, more substantial material is needed.

What to look for when choosing curtains

• Fabric thickness: Heavy, tightly woven materials retain heat much more effectively than light, sheer fabrics.
• Thermal or blackout curtains: Multi-layered options with a special coating or lining provide a significantly better insulating effect.
• Length: Curtains should cover the entire window down to just above floor level, without resting on a radiator.
• Width: Generous width helps the fabric seal properly at the sides, preventing cold areas around the edges.
• Colour and surface: Lighter fabrics with a reflective inner surface can distribute solar warmth around the room during the day, while acting as a barrier in the evening.

Many manufacturers sell so-called “thermal” curtains. Studies indicate that indoor temperatures in rooms fitted with these fabrics can be several tenths of a degree to several degrees higher than in comparable rooms without curtains. That may not sound like much, but during the heating season it can often make the difference between “turning the heating back up” and “leaving the thermostat where it is”.

How much can realistically be saved on heating costs

Potential savings depend heavily on the property: an older building with large single-glazed windows or a modern home with double or triple glazing, a north- or south-facing aspect, and a detached house or a flat within a larger building. As a general rule, the less well insulated the window is, the greater the possible saving from curtains.

Window type / situation	Possible effect of dense curtains
Older building, single glazing	Noticeably warmer room air and a clearly reduced need for heating during evening hours
Older building, upgraded insulating glazing	A perceptible improvement in comfort, with modest savings across the heating season
New-build home with triple glazing	A smaller but still measurable effect, particularly on very cold nights
Large glazed areas / floor-to-ceiling windows	A significant reduction in the sensation of cold in occupied areas, with less perceived “draught”

Energy experts report that some households have been able to keep their average room temperature stable by up to one degree without heating for longer, simply through consistent curtain management. Since each degree less of heating output saves roughly five to six per cent of energy, this is not only a matter of comfort but also of real financial savings.

Mid-March routine: making the most of evening sunshine

The key is to combine open curtains during the day with reliably closing them in the evening. Anyone who spends the day at the office should not automatically shut everything in the morning simply because it is still cool outside.

A possible daily routine for your curtains

• Morning: Open curtains fully so that as much daylight and solar warmth as possible can enter the home.
• Afternoon: In rooms receiving direct sunshine, deliberately retain that warmth by keeping window areas uncovered.
• Around 19:45 (from mid-March): Draw the curtains as soon as the sun has disappeared behind buildings or below the horizon.
• Later evening: Air rooms only briefly and intensively, then close the curtains again straight away.

People working from home can manage this more precisely: shortly before dusk, walk around the home and close curtains wherever window areas are large or cold air can noticeably radiate inwards.

When energy prices are high: small actions with a major effect

In many countries, households have faced pressure from rising electricity and gas prices for years. Many people already lower room temperatures, take shorter showers or switch off standby devices more strictly. Drawing the curtains fits naturally into the same approach: there is no loss of comfort, almost no effort is involved, and the effect is real.

“Heating, airing, managing curtains – those who keep all three in mind can often reduce their energy costs substantially without feeling cold.”

Online, users share experiences similar to those reported on the British portal: people who close their curtains consistently in the evening describe fewer draughts by the sofa, warmer bedrooms and radiators coming on less frequently. Tenants in poorly insulated older properties in particular often see this as a tangible relief.

What to avoid

One common mistake is having curtains that hang directly over radiators or even cover them in part. In that case, warm air builds up between the radiator and the fabric and barely circulates through the room.

• Fit curtains so that their lower edge does not touch the radiator.
• Use wide curtain poles so the fabric does not sit directly against the radiator.
• Where there are radiator recesses, ensure the curtain ends in front of the window reveal rather than in front of the radiator.

Moisture also needs attention. In rooms with high humidity, such as bedrooms or poorly ventilated older homes, condensation can collect on the glass behind dense curtains that remain closed for long periods. Regular short, intensive ventilation and a quick check behind the fabric help to prevent mould growth.

Practical examples for different homes

In a typical city flat with two large windows in the living room, a simple test can be worthwhile: on a cool March day, leave the heating at the same setting on two evenings, but close the curtains from 19:45 on only one of them. Many people notice from the sofa alone that the perceived temperature remains higher.

A similar experiment works in a detached home with large patio doors: place a thermometer in the living room, use the same heating setting on two comparable evenings and record how far the temperature falls overnight – once with the curtains or vertical blinds closed and once without them. Small measurements like these make the effect tangible and encourage the habit.

Further adjustments: combining curtains intelligently

Curtains can be paired with other simple measures. Many households achieve a kind of “cascade effect” when several small actions are combined:

• Apply draught-sealing strips to old window frames.
• Close roller blinds or Venetian blinds as an additional layer in the evening.
• Place rugs in front of cold external walls to reduce the feeling of draughts.
• Bleed radiators regularly so that they operate efficiently.

Each measure has a moderate effect on its own. Together, they noticeably stabilise indoor temperatures – and closing curtains in the evening plays a central part in that.

What terms such as “thermal curtains” really mean

The market for “thermal curtains” is growing, often accompanied by ambitious promises. The term usually refers to multi-layered fabrics, often with an insulating lining or a coated backing. The differences lie in their density, materials and construction.

Anyone wanting to upgrade does not necessarily need specialist products. Traditional heavy curtains made from densely woven fabric can also work well. What matters is that they close properly, are not too short and are hung securely enough to be used in everyday life – especially from mid-March, when evenings may still be light but the window no longer lets in any significant warmth.