p>This is a topic where there will always be conflicting information because there isn’t really a single right answer.</p> <p>I’ll try not to get too convoluted in this answer but I can’t already tell it will be long. First thing to say in general, is that the cooler you keep your house the less energy it will use - just as the inverse is true for your fridge - although <strong><a href="/guides/3683/fridge-organization-reduce-food-waste-live-more-sustainably/" target="_blank">fridge organization is necessary to reduce food waste</a></strong>. Heat loss increases with a greater differential in temperature, so the warmer it is inside compared to outside the greater your heat loss will be.</p> <p>As for where to set the temperature at night, I would make that decision based primarily on comfort and whether or not you have a thermostat timer and wake at a regular time. If you like sleeping in a cool room then drop the thermostat for sure, but if you don’t sleep well like that then keep it a bit warmer.  </p> <p>How much you will benefit from lowering the temperature at night and when you’re gone depends largely on how efficient your home is and if you have a lot of thermal mass inside the building enclosure.</p> <p>Lowering thermostats at night made a lot of sense 40 + years ago when homes were poorly-insulated and sometimes not insulated at all. Back then a furnace would cycle on and off many times in a day (or even in an hour) to keep the house at the designated temperature. The savings were realized because a house at 21C would lose heat a lot quicker than a house at 17C, so there was simply no point maintaining a higher temperature with the greater heat loss if no one was there.</p> <p>Now that homes are much better insulated and built airtight there isn’t the same amount of energy savings to be had by varying the temperature as there isn’t as much heat loss.</p> <p>So here is how you can come to your own conclusion, which will be the right one:</p> <p>If your house is not very well insulated and not very airtight and the temperature falls off pretty quickly when the heat is off, yes, you would probably notice the savings by lowering the temperature a bit in the day. How much I would drop it depends on how fast it warms up again when I come home, and whether I have a ‘smart’ control or timer so I can set it to be comfortable when I return.</p> <p>If you have a super-insulated house, it may take so long for the temperature to drop that it is hardly worth it.</p> <p>If you have a lot of thermal mass in your house (concrete slab floor, bricks or masonry on the interior etc) it will take a long time to cool off, and consequently a long time to warm up again, so again it may not be worth it. In such a  house the savings may be negligible and the main result may be discomfort coming home to cool furniture and floors.  </p> <p>If that doesn’t’ answer your question sufficiently, feel free to write back with more specific details about your heating bills and how modern or well-built your house is. </p