Close your curtains by 6pm and cut winter bills : could Martin Lewis’ £30 trick save you £120?

As dusk falls earlier and radiators groan back to life, families across Britain are hunting for cheaper ways to feel warm.

Rising unit rates under Ofgem’s autumn price cap have sharpened the focus on small, repeatable habits that delay switching on the heating. One simple move, widely shared by MoneySavingExpert founder Martin Lewis, has roared back into relevance: treat sunset like a daily deadline. Shut the drapes as light fades and you lock in daytime warmth for longer.

What the ‘6pm rule’ actually means

On bright days, keep window coverings wide open to let in solar heat. As soon as daylight fades — around 6pm in mid‑October, earlier by the end of the month — close them firmly. That single action reduces heat loss through glass, the thinnest part of most walls, and can push back the moment you need to fire up the boiler.

Open when the sun gives free heat. Shut as darkness creeps in. Repeat daily and rigorously as the nights draw in.

Lewis has long urged people to think tactically about soft furnishings. Heavy, lined drapes or an improvised liner made from fleece throws create a barrier, slowing heat escaping by conduction and convection. Done consistently, the effect stacks up night after night.

Why thicker, lined drapes hold warmth

Glass bleeds heat because warm indoor air brushes the cold pane and cools, setting up a downdraught. A dense fabric layer traps still air, which acts like extra insulation. Add a reflective surface — a simple foil panel behind a radiator under a window — and you cut radiant losses too. This is the same physics as a winter coat: bulky layers, trapped air, minimal drafts.

Think layers: fabric + trapped air + a snug fit around the frame. Every gap stopped means less heat slipping away.

Low-cost tweaks you can do today

• Pin or hem a fleece throw to the back of existing drapes; look for a flame‑retardant label.
• Ensure fabric drops to the sill or floor and overlaps the frame to block draught paths.
• If a radiator sits under a window, fit a narrow shelf above it so warm air flows into the room, not up the glass.
• Use stick‑on foam strips around window frames to reduce whistling gaps.
• Add reflective panels behind radiators on external walls.

What does ‘6pm’ look like as the clocks change?

Sunset varies by location, but the pattern is clear: each week brings earlier darkness. Treat the times below as a prompt to adjust your routine:

Check your local forecast for exact times. The principle stays the same: close up as the light goes.

How the numbers can add up on your bill

Most households pay around 7p per kWh for gas and roughly 29p per kWh for electricity on current caps. If closing up at dusk delays central heating by 45 minutes, a typical boiler might burn 2–3 kWh less gas that evening. That’s 14p–21p saved per night. Spread over 150 chilly nights, that’s £21–£32 without any sacrifice to comfort.

Add basic draught‑proofing and a reflective panel behind a couple of radiators, and many homes can trim another 1–2 kWh of gas a day in cold spells. That’s an extra £10–£20 over a month. None of this requires a tradesperson. A £30 pair of thermal curtains or a couple of fleece throws can pay back within one winter.

Delay the boiler by an hour across the season and you can keep £30–£60 in your pocket, before any other tweaks.

‘Heat the human, not the home’ — where it fits

Lewis often pushes the idea of warming people first, rooms second. A 100W heated throw costs about 3p per hour to run at today’s prices. Three hours nightly comes to under 10p. Compare that with firing a 24kW boiler that cycles on and off to warm empty rooms. For single‑room evenings, localised heat wins.

Practical ways to follow the motto

• Use a heated throw or pad on the sofa.
• Wear thin, layered clothing that traps air, plus wool socks or slippers.
• Shut interior doors; keep warmth where you are.
• Turn down the thermostat by 1°C if you feel comfortable; that can shave about 10% off gas use across a season.
• Set thermostatic radiator valves lower in rooms you rarely use.

Safety, fit and comfort: small details that matter

Keep fabric away from electric heaters and open flames. If you add fleece liners, choose flame‑retardant products and follow care labels. Where radiators sit under windows, make sure curtains don’t drape over them when the heating runs; use a short sill‑mounted shelf to push warm air into the room. Ventilate briefly each morning to manage condensation that can build behind heavy fabrics on cold nights.

What to buy — and what you can repurpose

You don’t need designer drapes. Look for “thermal”, “blackout”, or “interlined” on the label. Eyelet or pencil‑pleat styles both work; the key is fullness and width. If new sets aren’t in budget, repurpose fleece throws as liners with hemming tape, clips, or safety pins. For bay windows, consider a flexible track so fabric hugs the shape and closes off corner gaps. Even a rolled towel at the sill can tame a persistent draught while you save for better seals.

A quick at‑home test to see the effect

On a cold evening, place a lit incense stick near a closed, unlined window and watch the smoke. If it flows towards the pane and downwards, you have a downdraught. Now close a heavy curtain with a decent overlap. The flow should slow or stop. That’s your insulation layer doing its job. Repeat around doors and vents to find other leaks worth fixing with a few pounds of materials.

If you rent or can’t drill, try these no‑damage fixes

• Self‑adhesive foam strips for frames and letterboxes.
• Temporary shrink‑film kits that add an invisible layer to single glazing.
• Clip‑on curtain tracks or tension rods that avoid screws.
• Removable reflective panels behind radiators using command strips.

Where the rule pays best — and where to be cautious

Homes with single glazing, large panes, or north‑facing rooms see the biggest benefit. Period properties with leaky frames gain a lot from heavy night‑time coverings. New‑builds with well‑sealed, triple‑glazed units see smaller returns, but still benefit from early evening closure during cold snaps.

Watch for moisture build‑up in kitchens and bathrooms; run an extractor or open a window briefly after cooking or showering. Keep a small gap around trickle vents if condensation becomes a problem, balancing heat retention with fresh air.

A simple plan for the next two weeks

• Today: set a daily alarm for 10 minutes before local sunset; close everything on the chime.
• This weekend: add a fleece liner to your chilliest window and fit foam strips on the worst gaps.
• Next payday: buy one set of thermal drapes for the coldest room and a pack of radiator reflectors.
• All month: track boiler start time; aim to push it back by 30–60 minutes most evenings.

None of these steps tackles the whole energy bill, and they don’t replace proper insulation. They do, though, squeeze more comfort from the heat you already pay for. Follow the 6pm habit as nights shorten, line the glass you have, and prioritise heating the people in the room. That mix stretches warmth further without stretching your budget.