Thermostat Setting

We live in Glasgow and obviously this week the temperature has dropped significantly. This morning it's -7 outside.

Usually we turn our thermostat off at night, but when we get up in the morning the temperature is about 14. It takes a few hours to reach 18 when we turn it off. Then it's turned on again for a couple of hours in the afternoon, and then about 6pm until we go to bed.

Last night I left it on, set at 16, and the house is lovely and toasty this morning.

Is it better to have do this and have a "set" temperature all the time including at night, rather than turning the thermostat on and off? What uses more energy?

We have loft insulation, in a 1930s semi detached property, no other insulation (cavity etc).
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  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    edited 18 January at 8:10AM
    Ask Martin Lewis! This is an oft-asked Q in his newsletter.
    In essence, the more you have your heating on, and the higher the temp, the more it'll cost. End of.
    Heat is lost from your house at a rate determined by the temp difference betwixt inside and out, so the higher the inside temp, the more heat that is lost.
    You balance this simple fact with 'comfort', 'cos there's little point having CH unless it warms you!
    So, if you want or need to be warm in the mornings, you set your timer/thermostat to turn your heating on or up at a suitably early time. That time will change with season, and clearly in this cold spell it'll likely need to be turned on a good hour or so earlier than usual...
    But, to keep the heating running all night, even if not at full temp, will always cost more to run.

    In your example, having it at 14oC overnight (and day) will require it to be turned up earlier in order to get to the required temp in time. Having overnight/day at 16oC will mean it'll get up to temp more quickly, so heating can be turned up later. But, the latter arrangement will cost more overall to run.

    I would suggest you have a play with temps and timings, and see what works for you. For the cheapest way to run your house, you'd have your heating fully off except when required. That will mean the heating has to come on earlier before the 'required' time in order to lift the house temp from its colder start, but that's still cheaper overall. (But, I'd suggest a compromise...)
    So, for 'cheapest', you'd turn your heating off a half hour or so before bed ('cos the house will take a while to cool), and then back on at a time in the morn to get the house warm for wakie. Then off a half hour before folk leave the house, and back on at a time to get the house warm for their return. Etc etc.
    That's the cheapest way. But it has some drawbacks, such as giving the house some large temp swings, which might mean condensation forming in some rooms if not ventilated enough. And the house being cold if you need to get up for a wee.
    So you may decide instead for a compromise, but bear in mind the 'higher' this compromise, the more it'll cost.
    Keeping your house at a 16oC minimum all night and day might feel good, but it'll hit your purse. I'm not going to suggest fully off, tho', but a balance, say 14oC, and see how that goes.
    That will mean the heating needs to be turned back up earlier to get the house up to required living temps, but that's still cheaper to do overall.
    So have a play, and you decide on your comfort/cost balance :smile:
    This is made a lot more tricky if you don't have Smart controls. The best (all?) will even work out how early the heating needs to be turned up in order to get to the required temp! Ie, it doesn't go "Heating on at 6am to get the house warm for 7am", but "This temp is needed at 7am, so what is the current temp, and when do I need to turn it up to get to that temp in time?", which will, of course, vary over the season. And, you set and control it from your phone...


  • grumbler
    grumbler Posts: 58,629
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    edited 18 January at 8:05AM

    Is it better to have do this and have a "set" temperature all the time including at night, rather than turning the thermostat on and off? What uses more energy?
    If this were 'better', programmable thermostats wouldn't exist. The simplest ones have two settings - day and night. You can program 'day' to start, say, an hour before you wake up so that the house gets more or less warm in the morning. Smart thermostats often do this adjustment themselves - to reach the set temperature at the set time.
    Get to the 21 century!

  • twopenny
    twopenny Posts: 5,305
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    I had a 1920s house with an old system.
    Big boiler and basic on the wall thermostat.
    That did work out cheaper to leave it on at 13c all day.

    With a newish bungalow, basic boiler working on trvs it's not.

    The only way to really find out is to take meter readings for each method.
    You may find that there's a small difference and it's worth paying the extra for this very cold weather.
    Then go back to your usual settings when more tollerable temperatures return.

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  • grumbler
    grumbler Posts: 58,629
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    edited 18 January at 10:31AM
    twopenny said:

    The only way to really find out is to take meter readings for each method.

    There is no need to make experiments to prove basic physics facts. It can't be cheaper to maintain 13C all day long than to switch between 13C and, say, 10C. But it can be cheaper than switching, say, between,  16C and 10C.
  • FreeBear
    FreeBear Posts: 14,248
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    grumbler said:

    Is it better to have do this and have a "set" temperature all the time including at night, rather than turning the thermostat on and off? What uses more energy?
    If this were 'better', programmable thermostats wouldn't exist. The simplest ones have two settings - day and night. You can program 'day' to start, say, an hour before you wake up so that the house gets more or less warm in the morning. Smart thermostats often do this adjustment themselves - to reach the set temperature at the set time.
    Get to the 21 century!

    I have a smarter control system - Day time temperature set between 19°C & 20°C and overnight of 17°C. Heating may kick in once or twice overnight for about 15 minutes depending on how cold it is outside and how warm the house is. Running a "smart" schedule has help to cut my gas consumption as has improving the insulation levels.
    Programmable thermostats can be had for less than £40 (cheap ebay stuff) or around £100 from the likes of Screwfix.
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  • We live in Glasgow and obviously this week the temperature has dropped significantly. This morning it's -7 outside.

    Usually we turn our thermostat off at night, but when we get up in the morning the temperature is about 14. It takes a few hours to reach 18 when we turn it off. Then it's turned on again for a couple of hours in the afternoon, and then about 6pm until we go to bed.

    Last night I left it on, set at 16, and the house is lovely and toasty this morning.

    Is it better to have do this and have a "set" temperature all the time including at night, rather than turning the thermostat on and off? What uses more energy?

    We have loft insulation, in a 1930s semi detached property, no other insulation (cavity etc).
    We have the same type of house - 1930s 2-bed semi, full loft insulation, solid walls, etc. We found that we needed to keep the heating on during the day at 18 degrees ("off" mode) and 21 degrees ("on" mode, in the morning, afternoon, and early evening).

    As this is our first winter in our house, we initially thought that we would set the heating to off and on at certain times but temperature was down to like 13-14 degrees (far too cold) and in "on" mode, it took far too long for the temperature to come up to 21 degrees (and occasionally, never reached that temperature because by then it went into the "off" mode!).

    I am sure an EWI would help a lot but sadly this is not an option for us.

    For comparison in case this helps - in Dec, we consumed 1008kWh worth of gas which apparently is an UK average.
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    twopenny said:
    I had a 1920s house with an old system.
    Big boiler and basic on the wall thermostat.
    That did work out cheaper to leave it on at 13c all day.

    With a newish bungalow, basic boiler working on trvs it's not.

    The only way to really find out is to take meter readings for each method.
    You may find that there's a small difference and it's worth paying the extra for this very cold weather.
    Then go back to your usual settings when more tollerable temperatures return.

    13oC all day is hardly 'on'! :-)
  • ThisIsWeird
    ThisIsWeird Posts: 4,458
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    edited 18 January at 11:11AM
    We have the same type of house - 1930s 2-bed semi, full loft insulation, solid walls, etc. We found that we needed to keep the heating on during the day at 18 degrees ("off" mode) and 21 degrees ("on" mode, in the morning, afternoon, and early evening).

    As this is our first winter in our house, we initially thought that we would set the heating to off and on at certain times but temperature was down to like 13-14 degrees (far too cold) and in "on" mode, it took far too long for the temperature to come up to 21 degrees (and occasionally, never reached that temperature because by then it went into the "off" mode!).

    I am sure an EWI would help a lot but sadly this is not an option for us.

    For comparison in case this helps - in Dec, we consumed 1008kWh worth of gas which apparently is an UK average.

    To be clear, having your heating fully off when it is not required, and then coming on at whatever time is needed to get it up to the required temp is the cheapest way in terms of energy consumption.
    As Grumbler says, it's 'physics'.
    As the house cools, the loss of heat from the inside also falls; as the inside temp approaches that of the outside, the heat transfer - loss - diminishes. When the temps are equal - extreme case, of course - there is no more heat loss!
    Ergo, if you turn up the inside temp when it is not required, you will be losing heat. The higher the inside temp, the greater the loss.
    Yes, having a cold house does mean that the boiler then has to raise the house temp up from a lower level, thereby using more energy during that 'heating up' process, but that is still less overall energy used compared to keeping the house heated to any degree when it is not required.
    It does not matter what type of house, its age, its insulation level - that is the math.

    I am not suggesting that folk actually do this, as it 'could' come with drawbacks; condensation in unventilated rooms, potential damage to delicate devices - musical instruments, for example - and just the feeling of being cold during these times!
    Each person needs to make the 'compromise' decision depending on their own property and their own needs. I'd imagine, for example, a well-insulated property will heat up very quickly when required, so could afford to have the 'set-back' temp lower, say just 12oC? A poorly-insulated property prone to condensation may need to be kept at a min of 16oC or so, to prevent issues.
    But, heating on to any degree = energy loss & energy consumption.

  • To be clear, having your heating fully off when it is not required, and then coming on at whatever time is needed to get it up to the required temp is the cheapest way in terms of energy consumption.
    As Grumbler says, it's 'physics'.
    As the house cools, the loss of heat from the inside also falls; as the inside temp approaches that of the outside, the heat transfer - loss - diminishes. When the temps are equal - extreme case, of course - there is no more heat loss!
    Ergo, if you turn up the inside temp when it is not required, you will be losing heat. The higher the inside temp, the greater the loss.
    Yes, having a cold house does mean that the boiler then has to raise the house temp up from a lower level, thereby using more energy during that 'heating up' process, but that is still less overall energy used compared to keeping the house heated to any degree when it is not required.
    It does not matter what type of house, its age, its insulation level - that is the math.

    I am not suggesting that folk actually do this, as it 'could' come with drawbacks; condensation in unventilated rooms, potential damage to delicate devices - musical instruments, for example - and just the feeling of being cold during these times!
    Each person needs to make the 'compromise' decision depending on their own property and their own needs. I'd suggest, for example, a well-insulated property will heat up quickly, so could afford to have the 'set-back' temp lower, say 12oC? A poorly-insulated property prone to condensation may need to be kept at a min of 16oC or so, to prevent issues.
    But, heating on to any degree = energy loss & energy consumption.
    I fully agree!

    That said, could a modern well-insulated house ever go down to 12oC?
  • jennifernil
    jennifernil Posts: 5,567
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    edited 18 January at 11:52AM
    We live in Glasgow and obviously this week the temperature has dropped significantly. This morning it's -7 outside.

    Usually we turn our thermostat off at night, but when we get up in the morning the temperature is about 14. It takes a few hours to reach 18 when we turn it off. Then it's turned on again for a couple of hours in the afternoon, and then about 6pm until we go to bed.

    Last night I left it on, set at 16, and the house is lovely and toasty this morning.

    Is it better to have do this and have a "set" temperature all the time including at night, rather than turning the thermostat on and off? What uses more energy?

    We have loft insulation, in a 1930s semi detached property, no other insulation (cavity etc).
    We are just north of Glasgow, it was indeed  very cold last night.

     If you only have one thermostat controlling your heating, then I would say you need to invest in a few more controls.

    It sounds like you have no timer, is that correct?   The most  basic system would be a timer you can set to turn on and off the heating, set it to come on about an hour before you get up, and off 30 minutes before you go to work.     On about an hour before you get home from work , off 30 minutes before bedtime, or whatever  variations  you need.  Then your thermostat can control the temperatures you need.    And generally you would be leaving it at the same comfortable for you setting.   

     As already said, the 2 functions can be combined into a "programmable thermostat".

    You do however need to find the best position for the thermostat so the various rooms achieve the temperatures you want.

    Much better IMO would be to use a timer plus thermostatic radiator valves so you can set different temperatures in each room.  These are usually combined with a main thermostat, generally in the lounge, where you do not fit a TRV.  I am not a fan of this method as the stat is in charge and will turn things off when the place it is in reaches the set temperature, but other rooms may not be warm enough.

    For 35 years we operated our system using only a timer and TRVs on all but one small "bypass" radiator.......one that was always allowing water flow should all the TRVs close the other radiators.  The pump would run all the time and the boiler went on and off according to the boiler thermostat.    Not the most efficient of methods, but it worked well and allowed all rooms to have their own temperature setting.

    However, better systems have been available for a while now, some of them have many features and can be quite complex to set up.

    Having finally fitted a new, more efficient boiler in 2022, we looked at what was available and decided to go down the route of Smart Thermostatic Radiator  Valves, nothing too complicated, just new control heads that replace the existing TRV heads.    This means you do need to have ordinary TRVs on your radiators to start with.     

     There are several systems available, some more expensive than others.   With smart TRVs you fit one to each radiator, though your system may still require a bypass pipe or radiator.   We just retained the very small radiator in our very big hallway for this purpose.

    So now we can set every room in the house to heat to its required temperature at the required time, settings are done via a phone app or on some other device.    Check out systems such as Wiser.....Hive.....tado.......google Smart Radiator Valves and Smart Heating Controls.........you should see plenty of options.     Screwfix has some good prices on some of them, but do shop around
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