Households across the UK are being urged to follow a simple '6.30pm rule' to keep homes warm without raising energy bills. As temperatures drop, the advice from Octopus Energy's Phil Steele, Future Technologies Evangelist, is to close curtains when it gets dark to trap warmth inside.
Speaking exclusively to the Daily Mirror, Steele said: "Something as simple as closing your curtains when it gets dark can help keep warmth inside your home, particularly if you have thick or thermal curtains." He added: "Just make sure they don't hang over your radiators, as this can trap heat behind them rather than warming the room. It's a small change that can help you make better use of the heating you're already paying for."
Why timing matters
Sunset is expected at around 6.30pm today, 12 October, across the UK. Closing curtains around that time can retain heat indoors, potentially delaying the need to switch on central heating and keeping energy costs low. As the month progresses, daylight diminishes earlier; by 31 October, darkness will descend at around 4.30pm, requiring households to adjust routines.
Windows are a major source of heat loss. Drawing curtains or blinds at sunset creates an extra layer of insulation, preventing warm air from escaping and keeping draughty cold air out, reports the Mirror.
How the rule traps warmth
Thick or thermal curtains minimise heat loss through windows. While standard curtains can reduce window heat loss by 15% to 17%, heavy, thermally-lined curtains can cut this by as much as 33%. They work by creating a trapped pocket of still air between the room and the cold glass, acting as a barrier against draughts, convection currents and radiant heat loss.
For best results, choose dense fabrics such as velvet or wool with thermal linings, hang them flush against the wall and floor to eliminate gaps, and ensure they do not obstruct radiators. Open them during the day to let sunlight warm the home, then draw them tightly at dusk to retain heat.
If new thermal curtains are beyond budget, Martin Lewis recommends lining existing curtains with an inexpensive fleece blanket or throw to create an effective insulation barrier. Check the label for fire safety guidance and keep them away from open flames.
Other heat-loss checks
Octopus Energy also advises checking other areas of the home. A spokesperson said: "Check loft insulation, filling any draughty gaps around windows or doors, and don't forget things like letter boxes or unused chimneys that leak warm air. Bleed radiators so they run efficiently and avoid covering them with furniture or curtains – especially under windows."
For homes with a gas boiler, checking its flow temperature is worthwhile, as many are set too high as standard. The spokesperson said: "Lowering it to 55–60°C keeps homes just as warm but can trim bills by around 12% (up to £65 a year, according to Nesta)."
Thermostat use also matters. Treating it as an on/off switch or a "boost" button can squander energy, as the system works harder to reheat the space. The spokesperson explained: "You'll stay comfier – and use energy more efficiently – by setting it to come on only when you need it and leaving it steady between 18–21°C. Turning it down by just one degree could save up to £145 a year."
