Most of a year's energy spending lands in the cold months, so a little preparation in autumn pays off all winter. None of this is dramatic, and most of it costs nothing, but worked through as a checklist before the first real cold it turns a house that haemorrhages heat into one that holds it. Here is the run-through, roughly in the order worth doing.
Set and time the heating
Start where the money is. Set the room thermostat to the lowest temperature that is genuinely comfortable, a degree lower than habit if you can manage it with a jumper, and programme the heating to come on shortly before you wake and return and to drop back when you are out or asleep. Turn down the radiator valves in rooms you rarely use so you are not heating empty space. This single afternoon of setting controls properly is the biggest saving on the list.
Tune the heating system
Before the system works hard all winter, get more out of every unit of gas. Bleed the radiators so they fill with hot water right to the top, move furniture and long curtains off them so the heat reaches the room, and turn down the boiler flow temperature to the low fifties so a condensing boiler runs in its efficient mode. If the boiler has not been serviced in a while, autumn is the time, both for efficiency and to catch a fault before it leaves you cold in January.
Stop the heat escaping
Now seal the leaks. Walk the house on a windy day and draught-proof the doors, windows, letterbox, loft hatch and the gaps around pipes and skirting, leaving the deliberate ventilation alone. Check the loft insulation is at full depth and top it up if the joists are showing. Hang or close heavy lined curtains at dusk to keep the day's warmth in. Together these make the house feel warmer at a lower setting, which is where the heating saving comes from.
Protect against the freeze
A cold snap can cost far more than a high bill if a pipe bursts. Lag any exposed water pipes in unheated lofts, garages and outbuildings, and insulate the boiler's external condensate pipe, which can freeze and lock the boiler out on the coldest mornings. Know where your stopcock is. If you will be away, leave the heating ticking over on a low frost-protection setting rather than off entirely, so the house never drops to the point where pipes freeze.
Sort the hot water and the smaller stuff
Fit or check the cylinder jacket if you have a hot-water tank, and lag the nearby pipes, so stored hot water stays hot. Swap any remaining old bulbs for LEDs now the dark evenings are drawing in and the lights are on for longer. Dig out the draught excluders, the warm bedding and the heated throw before you need them, so comfort does not tempt you to crank the thermostat up.
The order that pays
If you do nothing else, set and time the heating and seal the worst draughts, because those two cost nothing and deliver most of the benefit. Tune the boiler and top up the loft next. Leave any big spending, new windows, major insulation, a new boiler, for a considered decision rather than a panic in the first cold week. Worked through each autumn, this checklist is the difference between dreading the winter bills and barely noticing them.