A surprising amount of received wisdom about saving energy is either plain wrong or so trivial that obsessing over it distracts from the things that actually matter. Believing the myths can cost you money directly, and worse, it can convince you that you are doing your bit while the expensive stuff runs unquestioned. Here are the common ones, and what the truth points you towards instead.
Leaving the heating on low all day is cheaper
This is the most stubborn myth of all. The claim is that it costs more to reheat a cold house than to keep it ticking over warm all day, so you should never let it cool. For almost every home this is false. A house constantly leaks heat to the colder outdoors, and the warmer you keep it the faster it leaks, so heating an empty house all day simply pays to replace heat you did not need. A well-timed system that warms the house when you are in and lets it cool when you are out or asleep uses less. The thermostat settings guide covers how to time it properly.
Unplugging your phone charger saves meaningful money
A charger left in the wall with nothing plugged into it draws so little that switching it off saves a few pence a year at most. It is harmless to unplug it, but presenting it as a serious saving is the kind of advice that makes people feel virtuous while the tumble dryer quietly costs them a hundred times as much. The real standby savings come from the genuinely hungry always-on devices, as the standby power guide explains, not from the charger.
Turning lights off for a moment uses more than leaving them on
This was loosely true in the era of fluorescent tubes, where the start-up surge and the wear on the tube meant very brief switching had a small cost. With modern LED lighting it is simply false: an LED costs effectively nothing to switch and wears no faster for it, so turn lights off whenever you leave a room, even briefly. The old rule has long outlived the technology that justified it.
Cranking the thermostat up heats the house faster
Turning the thermostat to its maximum does not make the house warm up any quicker; it only changes the temperature at which the heating stops. A thermostat is a target, not an accelerator. Setting it to twenty-eight to warm a cold room faster than setting it to twenty achieves nothing except that, if you forget it, the house overshoots to an expensive twenty-eight. Set it to the temperature you actually want and let it get there.
Boiling a full kettle is fine, the water keeps for later
Reboiling water you boiled earlier means heating it from cold again, so filling the kettle to the top for one cup wastes the energy used to heat all the water you did not use. The kettle guide covers this, but the myth that a full kettle is harmless because the hot water is somehow saved is worth naming, because the water cools back down and the next cup starts from cold regardless.
Energy-saving gadgets and boxes that slash your bill
Be wary of devices sold with claims to cut your electricity use by some large percentage simply by being plugged in, whether described as power optimisers, voltage savers or similar. For an ordinary domestic supply these generally do little or nothing useful, and the bold percentage claims do not survive scrutiny. The things that genuinely cut bills are unglamorous: insulation, draught-proofing, heating controls, efficient habits and the right tariff. If a single plug-in box really delivered what is claimed, it would not need to be sold by the myth.
What actually moves the bill
Strip away the myths and the real list is short and dull, which is exactly why it works. Heating dominates most bills, so turning the thermostat down a degree, timing the heating to your day, sealing draughts and insulating the loft do the heavy lifting. After that come the hungry appliances, the dryer, the heating of water, the electric shower, where habits and efficient use save real money. Put your own appliances through the cost calculator and the priorities sort themselves out. Spend your effort where the energy goes, and let the phone charger be.