Octopus Energy's Phil Steele, Future Technologies Evangelist, has shared a '6.30pm rule' to help UK households keep their homes warm while reducing energy bills. The tip involves closing curtains at sunset to trap warmth inside, potentially delaying the need to switch on central heating.
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
The sun is expected to set around 6.30pm today, October 12, across the UK. Homeowners are encouraged to close curtains at that time to trap heat indoors. By October 31, darkness will fall around 4.30pm, requiring households to adapt their daily habits.
Windows are among the primary sources of domestic heat loss. Drawing curtains or blinds as soon as the sun goes down creates an extra layer of defence that stops warm air from escaping and blocks drafty cold air from entering.
How thick curtains help
Thick or thermal curtains can effectively keep a house warmer by reducing heat loss through windows. While standard curtains can reduce window heat loss by 15% to 17%, upgrading to heavy, thermal-lined curtains can cut it by up to 33%.
They work by creating a trapped pocket of still air between the room and the cold glass, acting as a barrier against drafts, convection currents, and radiant heat loss. To maximise benefits, choose dense fabrics like velvet or wool with thermal linings, hang them tightly against the wall and floor to seal off gaps, and ensure they do not block radiators. Open them during the day to let natural sunlight heat the home, and shut them tightly at dusk to lock the warmth inside.
If you cannot afford new thermal curtains, Martin Lewis recommends lining existing drapes with a cheap fleece blanket or throw, creating a budget-friendly insulation barrier. Check the label for fire safety and keep them away from open flames.
Other energy-saving tips
Octopus Energy also recommends checking other parts of the house to avoid heat loss. 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."
If you have a gas boiler, check its flow temperature – the temperature of water flowing from the boiler to the radiators. The spokesperson says many are set too high by default: "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)."
Using the thermostat like an on/off switch or "boost" button can waste energy, as the system works harder to reheat the space. "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," the spokesperson explained.
