Cooling
It is the question we get asked more than almost any other. What temperature should I actually set my air con to? People worry they are either not getting the comfort they paid for or running up a bill chasing a number that is lower than it needs to be. The honest answer is that there is a sensible sweet spot, and understanding it will make your home more comfortable and cheaper to run at the same time.
After more than 25 years fitting and servicing systems across the North-East, here is the practical advice we give our own customers, with the reasoning behind it so you can judge what suits your home.
Before we get into numbers, it helps to know that there is no single correct temperature for everyone. Comfort depends on the person, what they are wearing, how active they are and, crucially, how humid the air is. So treat everything that follows as sound guidance to start from rather than a law. The goal is to find a setting that feels good to you while keeping the system working efficiently, and once you understand the principles you can tune it to your own taste with confidence.
A sensible comfort range
For most living spaces a setpoint somewhere in the low twenties is the comfortable, efficient choice. Around 22 to 24 degrees suits most people for day-to-day living, feels fresh without being chilly and does not make the system work excessively hard. That is the range we would start people at and adjust from there to taste.
Comfort is personal, so treat that as a starting point rather than a rule. Some people like it a touch cooler, some warmer, and what feels right depends on humidity, clothing and how active you are. The key thing is to find the warmest setting at which you are genuinely comfortable, because every degree below that costs you for no extra benefit.
The small-gap point
Here is the single most useful idea to take away. The bigger the difference between your indoor setpoint and the temperature outside, the harder the system works and the more it costs to run. Air conditioning has to move heat out against that gap, and a wider gap means more work.
So on a day when it is 28 degrees outside, setting the room to 18 is asking the system to fight a ten degree battle all day. Set it to 23 instead and you have a far smaller gap, a much easier job for the unit and a room that is still perfectly comfortable. You barely notice the difference between a sensibly cool room and a deeply cold one in terms of comfort, but you certainly notice it on the bill. Aim to take the edge off the heat rather than turn your home into a fridge.
There is a comfort argument for this as well as a cost one. Walking from a hot garden straight into a room chilled to the high teens is a bit of a shock to the body, and sitting in it for long can leave you feeling stiff or chilly despite the heat outside. A room held in the low twenties feels fresh and pleasant without that jarring contrast, and it is kinder to anyone who feels the cold easily. Comfortable does not mean cold, it means the right side of warm, and the two are not the same thing.
Do not overcool
Overcooling is the most common and most expensive habit we see. People come in from the heat, feel too warm and crank the setpoint right down to 17 or 18, thinking it will cool the room faster. It does not. The unit cools at the same rate whichever low target you choose, it just keeps going for longer and overshoots, so you end up in a room that is actually too cold and has cost more than it needed to.
- Set the target you want, not lower. A lower setpoint does not cool faster, it just runs longer.
- Turn the fan up for speed. If you want quicker cooling, raise the fan speed rather than dropping the temperature.
- Give it time. A sensible target reached steadily beats a cold one chased all afternoon.
Find your comfortable number, set it and leave it. Fiddling the setpoint down every time you feel warm is the fast route to a high bill and a cold room.
If the room genuinely is not cooling fast enough, the answer is not a lower number but a bit of patience and a higher fan speed, plus the usual sense of shutting doors and drawing blinds on the sunny side. The temperature you set is the destination, not the speed, and the quickest way to reach it is to help the unit rather than confuse it. Once people grasp that one point they tend to stop wrestling with the handset and simply enjoy a steady comfortable room.
Bedrooms and sleep
Sleep is a special case because we are more comfortable slightly cooler at night. A bedroom often feels best a degree or two below your daytime living temperature, which helps you drop off and stay asleep. That said, you do not want it cold, and you do not want cold air blowing straight across the bed.
Use sleep mode
Most systems have a sleep or night mode that gently eases the temperature through the night and keeps the fan quiet. It is designed exactly for this, keeping you comfortable as you sleep without running hard or making noise. Combined with a schedule that switches the unit off towards morning, it is a comfortable and economical way to run a bedroom. Aim the airflow so it circulates rather than pointing at where you lie.
A common and economical approach is to let the room cool while you drop off, then have the unit ease right back or switch off a few hours in, by which point the room has lost enough heat to stay comfortable on its own until morning. That way you are not paying to cool an already cool room through the small hours. A little experimenting with the timer soon tells you what works for your room, and once it is set you simply get a good night without thinking about it. Children who kick their covers off tend to sleep better in a bedroom that is pleasantly cool rather than stuffy, which is a common reason parents ask us to do the bedrooms first.
What each degree costs you
It is hard to put an exact figure on it because every home and system is different, but the direction is clear and worth knowing. Every degree lower you set the target makes the system work harder and costs more to run, because you are widening that gap to the outdoor temperature and asking the unit to remove more heat.
The rule of thumb to carry in your head is simple. Nudging the setpoint up by a degree or two in cooling, to the warmest you still find comfortable, is one of the easiest ways to cut your running costs with no new kit and no loss of real comfort. It is free, it is instant and over a summer it adds up. If you want to save money on air con, this is the first lever to pull.
The same thinking applies in reverse in winter. Nudging the heating setpoint down by a degree, to the coolest you still find cosy, trims the running cost the same way. It is the gap to outside that drives the cost in both seasons, so in each case you are simply choosing not to push that gap any wider than you need. A jumper in winter and a lighter top in summer let you set a kinder number without feeling any less comfortable, and your bill thanks you for it.
Let auto mode do the thinking
Auto mode is a feature a lot of people never use and it is a shame, because it is genuinely clever. In auto, the system manages the fan speed and output itself to hold your chosen temperature smoothly, rather than you having to juggle settings. It ramps up when the room needs pulling down and eases off as it gets there, which is both comfortable and efficient.
For most households, setting a sensible temperature and letting auto mode handle the rest gives the best balance of comfort and economy without any fuss. Modern inverter systems are especially good at this, trimming their output to match the room rather than blasting on and off, which saves energy and keeps the temperature steady. Set the number, choose auto and let it get on with it.
This is a real change from older air conditioning, which tended to blast on at full power then switch off completely, so the room swung between too cold and too warm and the compressor clattered on and off all day. An inverter system instead varies its speed, working hard to bring the room down then easing right back to tick over and hold it, like driving smoothly rather than stamping between the accelerator and the brake. That gentle holding is both more comfortable to sit in and cheaper to run, and auto mode is how you let the system do it for you. For most people, fiddling less and trusting auto gives a better result than constant adjustment.
Seasonal differences
Your ideal setpoint is not the same all year, because the same system heats as well as cools. In summer you are aiming to take the heat off, so the low twenties in cooling is the target. In winter the same unit works as a heat pump, and the efficient approach is the mirror image of the summer rule.
- Summer cooling. Low twenties, warmest comfortable setting, small gap to outside.
- Winter heating. A comfortable room temperature without overheating, again keeping the gap sensible.
- Shoulder seasons. Dry mode on muggy days often beats hard cooling.
- Empty house. Let it off or set well back rather than holding a comfort temperature for nobody.
The underlying principle is the same in both seasons. Keep the difference between inside and outside modest, do not chase extremes and you get comfort and economy together.
One last seasonal point that catches people out. When you first switch to heating on a cold morning the outdoor unit may occasionally pause to defrost itself, which is completely normal and nothing to worry about, so do not crank the setpoint up in a panic. Give it a moment and it will pick the heating back up. In the same way, do not expect a room that has gone cold overnight to heat instantly. A sensible target reached steadily, with the fan doing the work, beats chasing a high number that just leaves the room too warm and the bill too high once it catches up.
Talk to Air Con North
Setting your air con well is half the battle, and a system that is properly sized and set up makes it effortless. If you want advice on running yours economically, or you are thinking about a new system that is matched to your rooms from the start, we are happy to help. We design, supply, install and maintain cooling and heating for homes and businesses across the North-East, from Newcastle and Gateshead to Durham, Sunderland, Middlesbrough and Carlisle, with over 25 years in the trade. Call us free on 0800 246 5430 for a no-obligation chat or survey and we will set you up to be comfortable without wasting a penny.
