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  • FIRST POST
    • MSE Guy
    • By MSE Guy 4th Dec 12, 6:43 PM
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    MSE Guy
    Energy myth-busting: Is it cheaper to have heating on all day?
    • #1
    • 4th Dec 12, 6:43 PM
    Energy myth-busting: Is it cheaper to have heating on all day? 4th Dec 12 at 6:43 PM
    This is the discussion for the following MSE guide.


    Energy myth-busting: Is it cheaper to have heating on all day?
Page 44
    • Bricks
    • By Bricks 11th Oct 17, 12:05 PM
    • 54 Posts
    • 18 Thanks
    Bricks
    By the way. Just read the "Energy saving Myths" page on MSE. This may have been done already on the many previous pages of this thread, but the "ask jeff" article linked to seems very suspect to me

    http://www.askjeff.co.uk/will-keeping-heating-increase-bills/

    Firstly it seems heavily tinged with climate change denialism.

    Secondly it makes a bizarre claim that those who advocate energy efficiency want people to be less comfortable in order to "punish" them for causing climate change!

    Thirdly it contains a number of non-sequitur statements to do with condensation in walls, and nothing specific to back up its vague argument that this is relevant to the question the article claims to address.

    I'd advise people to ignore this article. I also don't think it should be linked to on the MSE site because it seems to do nothing other than make a series of unsubstantiated claims.
    • sue1201
    • By sue1201 11th Oct 17, 12:16 PM
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    sue1201
    Include renewables in the advice
    This could be updated to include advice for people who have solar PV or air source heat pumps ie cheap renewable energy.
    For example, we have solar PV and a diverter which when we aren't using the power generated, sends it to the immersion heater to heat our domestic hot water. In 5 years we have only had to over-ride it once (when it rained for 4 days straight). We rely on this from Spring to Autumn. In the winter we have a wood burner which heats the domestic hot water.
    We also have a wood chip boiler, which though expensive to install is earning RHI, and the fuel is not particularly expensive.
    With a heat pump, your heating (typically under-floor) is at a lower temperature so it needs to be in conjunction with high grade insulation. It also will take longer to heat the space to the temperature required, so should be timed to come on sooner than you think. Depending what you read, it may well be better to leave it on all the time, at least in terms of energy efficiency.
    Re electric heaters, my pet electrician says that only electric heaters are 100% efficient ie all the power used is converted to heat. But it's true that they are expensive to run. You need to know both the cost and the efficiency to work out which form of heating is best.
    • Bricks
    • By Bricks 11th Oct 17, 1:28 PM
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    Bricks
    Re electric heaters, my pet electrician says that only electric heaters are 100% efficient ie all the power used is converted to heat.
    Originally posted by sue1201
    In terms of the power coming into your home maybe. But that electricity will have been generated in a power station that achieves nowhere near 100% efficiency, and is likely to have been generated from fossil fuels.
    • Troublemaker66
    • By Troublemaker66 11th Oct 17, 1:41 PM
    • 22 Posts
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    Troublemaker66
    Thermostatic valves
    I can't always tell what the settings are so I got the service engineer to turn up the one in my study where I spend most time, and turn the one in the hall by the main thermostat well down. What's the point of the Hall being warm because I have my outdoor clothes on in there either going out or coming in. Passing through to the bathroom in the middle of the night is transitory so doesn't count.

    The huge myth of turning off chargers, has been put over mostly by fossil fuel advocates. The amount of charge drawn by a mobile phone when fully charged is small, and when it isn't plugged in to the charger is minimal. The danger of the charger overheating and causing a fire might be worth thinking of.

    Proper insulation is the elephant in the room and accounts for much greater savings. But saving money is only part of the equation. As things are, I sit here for hours on end growing slowly colder in the interest of saving money. Makes me feel like the Lady of Shallott.
    • victor2
    • By victor2 11th Oct 17, 2:25 PM
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    victor2
    And the thread awakens after another summer in hibernation...
    • lstar337
    • By lstar337 11th Oct 17, 2:52 PM
    • 3,227 Posts
    • 1,729 Thanks
    lstar337
    And the thread awakens after another summer in hibernation...
    Originally posted by victor2
    I thought the same thing.

    Can't wait to see the theories this year, and of course fellow members of 'the old gang' returning to debunk them.

    Let the good times roll.
    • sue1201
    • By sue1201 11th Oct 17, 2:55 PM
    • 2 Posts
    • 1 Thanks
    sue1201
    good point
    In terms of the power coming into your home maybe. But that electricity will have been generated in a power station that achieves nowhere near 100% efficiency, and is likely to have been generated from fossil fuels.
    Originally posted by Bricks
    Quite right, thank you. That is why I want more discussion on efficient use of renewables.
    • orrery
    • By orrery 11th Oct 17, 2:57 PM
    • 522 Posts
    • 444 Thanks
    orrery
    A central thermostat has never made sense to me...
    Originally posted by d68
    I have dumb TRVs, to regulate each room but not in the hall, with the hall radiator fairly well strangled off so it only starts to heat the hall as a few of the TRVs start to regulate down

    I have a central thermostat in the hall, which has the benefit of not running the heating at all if the outside temperature doesn't warrant it. I've replaced the central thermostat with a Tado thermostat in order to allow for geo-fencing and remote control - it looks at the outside forecast to work out whether it is worth turning the heating on. If the hall is 0.5C below target and there is lots of sun forecast then it doesn't bother. So, central thermostats are important.
    4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TL, SolarImmersion
    Location: Bedford, Roof: South East facing, 20 degree pitch
    Nissan Leaf, TADO Central Heating control
    • Cardew
    • By Cardew 11th Oct 17, 6:40 PM
    • 26,890 Posts
    • 13,039 Thanks
    Cardew
    By the way. Just read the "Energy saving Myths" page on MSE. This may have been done already on the many previous pages of this thread, but the "ask jeff" article linked to seems very suspect to me

    http://www.askjeff.co.uk/will-keeping-heating-increase-bills/

    Firstly it seems heavily tinged with climate change denialism.

    Secondly it makes a bizarre claim that those who advocate energy efficiency want people to be less comfortable in order to "punish" them for causing climate change!

    Thirdly it contains a number of non-sequitur statements to do with condensation in walls, and nothing specific to back up its vague argument that this is relevant to the question the article claims to address.

    I'd advise people to ignore this article. I also don't think it should be linked to on the MSE site because it seems to do nothing other than make a series of unsubstantiated claims.
    Originally posted by Bricks
    Excellent post!

    There is a recurring(and stupid) argument every year that goes along the lines:

    'instead of heating my rooms to, say, 21C in the evenings, I find it cheaper to keep the thermostat 24/7 at, say, 16C.'

    Whilst that may well be true, it ignores the fact that almost everyone finds 16C unacceptable in the evening.

    Except those of course who post that 12C is comfortable!
    • lstar337
    • By lstar337 12th Oct 17, 9:05 AM
    • 3,227 Posts
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    lstar337
    I can't always tell what the settings are so I got the service engineer to turn up the one in my study where I spend most time, and turn the one in the hall by the main thermostat well down. What's the point of the Hall being warm because I have my outdoor clothes on in there either going out or coming in. Passing through to the bathroom in the middle of the night is transitory so doesn't count.
    Originally posted by Troublemaker66
    The problem with not heating a hall, is the same problem you get with zoned heating in smaller properties. Unless you keep all doors shut, all the time, then as soon as a door is opened (or left open), then the heat from that room flows out to fill the cold hallway anyway.

    This is unless you dash through doorways and quickly slam the door shut behind you, or install some kind of complicated airlock system on all doorways that join the unheated hallway.

    I prefer to just heat the hall and landing. That way I don't have to feel uncomfortable moving from room to room, or feel like I need to dash about or keep tabs on which doors are opened and closed.
    • malc_b
    • By malc_b 12th Oct 17, 9:21 AM
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    malc_b
    My 2p.

    The ask jeff article does make claims which are not backed up with studies. However, it is not an unreasonable argument. Wet bricks and wet cavity fill would be more conductive of heat than when dry and houses produce a lot of water vapour some of which escapes through the walls. My gut feeling is that water vapour isn't enough but that's just my gut I've no facts to back that up either way.

    National trust did some tests in one of their properties and found their cost of heating was lower when it was on low 24/7. That could be because the walls stayed dry. Equally it could be because running low is more efficient that running high, especially on a condensing boiler where the difference is at least 10%. For dense property, which all National Trust places would be, the difference between 24/7 and broken running is a ~5% saving which hence would gave a saving on 24/7 running.

    Turning off radiators in unused room is dubious IMO. The insulation in a house is in the outside walls. There is no insulation between rooms and of course air freely moves between rooms. Turning off a radiator in a room just reduces the radiator surface to heat the house. The unheated room is getting heat from the heated areas of the house. It has to be unless it is at outside temperature, i.e. middle of winter, -1C outside, -1C in unused bedroom, ice on the walls.... Doesn't happen. Turn the rad down by all means but keep it sensible, say 18 or 16C, warm enough to keep condensation at bay and so that there isn't too big a difference to the rest of the house. Otherwise that room will be sucking heat out of next door rooms since houses do not have insulation between rooms. The issue in reducing the rad area is that you make the remaining radiators work harder so hot so less efficient with a condensing boiler.

    What most people fail to realise is that everyone is in fact heating their house 24/7. Take a house a 20C, outside is 0C. You turn the heating off at 10pm. Does the temperature drop to 0C? No (unless you live in a tent). What happens is that the house temperature slowly drops overnight to maybe 16C by morning. All through the night heat has been leaking out of the house. That comes from the structure of the house. The next morning when turn the heating on you put that lost heat back into the structure. The overall energy usage is similar, you save a bit overnight because the average temperature is 18C (20C->16C, avg 18C), rather than it being kept at 20C. The downside is that you have to make the heating work harder so it is less efficient.

    I know people struggle with this let me give another analogy. You're in bed trying to keep warm. Option 1 turn on the electric blanket, call that 20W on continuously. Option 2 the house fairy brings you a hot water bottle, that took 6min of 2kW kettle to boil it. It lasts 10hrs. Option 1 uses 20W x 10hr = 200Wh. Option 2 uses 2000 x 6/60 = 200Wh. Exactly the same. Although option 2 only uses the power for a short time it is storing the energy. A house works the same way. You store heat in the structure and release it overnight when the heating off.

    It is therefore not a given that running the heating shorter or turning off radiators will reduce you heating costs. After a point you are making the heating system work harder and so less efficient. After this point the heat saving is outweighed by the loss in efficiency so bottom line is less heat used but more ££ spent.
    • lstar337
    • By lstar337 12th Oct 17, 2:20 PM
    • 3,227 Posts
    • 1,729 Thanks
    lstar337
    My 2p.

    The ask jeff article does make claims which are not backed up with studies. However, it is not an unreasonable argument. Wet bricks and wet cavity fill would be more conductive of heat than when dry and houses produce a lot of water vapour some of which escapes through the walls. My gut feeling is that water vapour isn't enough but that's just my gut I've no facts to back that up either way.

    National trust did some tests in one of their properties and found their cost of heating was lower when it was on low 24/7. That could be because the walls stayed dry. Equally it could be because running low is more efficient that running high, especially on a condensing boiler where the difference is at least 10%. For dense property, which all National Trust places would be, the difference between 24/7 and broken running is a ~5% saving which hence would gave a saving on 24/7 running.

    Turning off radiators in unused room is dubious IMO. The insulation in a house is in the outside walls. There is no insulation between rooms and of course air freely moves between rooms. Turning off a radiator in a room just reduces the radiator surface to heat the house. The unheated room is getting heat from the heated areas of the house. It has to be unless it is at outside temperature, i.e. middle of winter, -1C outside, -1C in unused bedroom, ice on the walls.... Doesn't happen. Turn the rad down by all means but keep it sensible, say 18 or 16C, warm enough to keep condensation at bay and so that there isn't too big a difference to the rest of the house. Otherwise that room will be sucking heat out of next door rooms since houses do not have insulation between rooms. The issue in reducing the rad area is that you make the remaining radiators work harder so hot so less efficient with a condensing boiler.

    What most people fail to realise is that everyone is in fact heating their house 24/7. Take a house a 20C, outside is 0C. You turn the heating off at 10pm. Does the temperature drop to 0C? No (unless you live in a tent). What happens is that the house temperature slowly drops overnight to maybe 16C by morning. All through the night heat has been leaking out of the house. That comes from the structure of the house. The next morning when turn the heating on you put that lost heat back into the structure. The overall energy usage is similar, you save a bit overnight because the average temperature is 18C (20C->16C, avg 18C), rather than it being kept at 20C. The downside is that you have to make the heating work harder so it is less efficient.
    Originally posted by malc_b
    The bit in bold negates your whole argument. You said it yourself, you save by turning the heating off overnight.

    The bit after about the heating 'working harder' is twaddle, my heating doesn't work any harder than I let it, and mine is set to a level where it is always in condensing mode.

    I know people struggle with this let me give another analogy. <snip pointless analogy>
    Originally posted by malc_b
    I know you think people struggle, but no advocate of timed heating (as opposed to 24/7 heating) does. They understand perfectly, and they are saving money because of it.
    • orrery
    • By orrery 12th Oct 17, 2:57 PM
    • 522 Posts
    • 444 Thanks
    orrery
    The bit after about the heating 'working harder' is twaddle, my heating doesn't work any harder than I let it, and mine is set to a level where it is always in condensing mode.
    Originally posted by lstar337
    No, it isn't twaddle. Yours maybe, if you understand it well, but I suspect most people don't.

    My heating will run for about 40 minutes before the return water is hot enough to cause the boiler to start to modulate i.e. the flow is about to go over-temperature. Once the boiler modulates, you can kiss goodbye to condensing mode, as the return water simply increases rapidly in temperature - not easily visible unless you find the hidden option to display it on the boiler (requires manual in hand) or strap a thermocouple to the return pipe.

    The only way it can be tamed and kept in condensing mode is for the controller to enforce a proportional control regime - turning the boiler on and off so that it never gets into modulating. Proportional control doesn't usually start until the room temperature is approaching target - within about 1C.

    I'd regard my system as being pretty typical of most systems out there.
    4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TL, SolarImmersion
    Location: Bedford, Roof: South East facing, 20 degree pitch
    Nissan Leaf, TADO Central Heating control
    • lstar337
    • By lstar337 12th Oct 17, 4:43 PM
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    • 1,729 Thanks
    lstar337
    No, it isn't twaddle. Yours maybe, if you understand it well, but I suspect most people don't.

    My heating will run for about 40 minutes before the return water is hot enough to cause the boiler to start to modulate i.e. the flow is about to go over-temperature. Once the boiler modulates, you can kiss goodbye to condensing mode, as the return water simply increases rapidly in temperature - not easily visible unless you find the hidden option to display it on the boiler (requires manual in hand) or strap a thermocouple to the return pipe.

    The only way it can be tamed and kept in condensing mode is for the controller to enforce a proportional control regime - turning the boiler on and off so that it never gets into modulating. Proportional control doesn't usually start until the room temperature is approaching target - within about 1C.

    I'd regard my system as being pretty typical of most systems out there.
    Originally posted by orrery
    If your return temperature is increasing 'rapidly' then turn down the output until the return is low enough to keep it condensing. The return is only increasing because your rads can't shift the heat fast enough, or your house is already warm enough.

    Regardless, the stuff about the boiler running a bit harder in the morning is never going to be enough to cancel out a whole night of wasted energy heating rooms when people are tucked up asleep.

    If you left your house unoccupied for a year, would you leave the heating on? After all, if you let the house go cold for a year the boiler would have to work quite hard to bring it back up to temperature when you returned. Probably cheaper to leave the heating on I think.
    • Cardew
    • By Cardew 12th Oct 17, 5:44 PM
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    Cardew
    Regardless, the stuff about the boiler running a bit harder in the morning is never going to be enough to cancel out a whole night of wasted energy heating rooms when people are tucked up asleep.

    If you left your house unoccupied for a year, would you leave the heating on? After all, if you let the house go cold for a year the boiler would have to work quite hard to bring it back up to temperature when you returned. Probably cheaper to leave the heating on I think.
    Originally posted by lstar337
    I have used this analogy many times on this forum.

    People attempt to use the same argument(i.e. constant heating) for Hot Water tanks. i.e. it is cheaper to keep hot water on all the time because if you have timed heating, the boiler will have to work harder and use more gas/electricity/oil than it would to keep the water at a constant heat.

    Surely nobody, but nobody, would argue that leaving the heating off for a year, and then bringing the house back up to a set temperature after a year, would use less energy than keeping it at that set temperature for the whole year.

    When the heating is left off for that year, the laws of physics determine that the rate of heat loss from the house decreases as the house cools and will be zero when the inside and outside temperatures are equal.

    So if we agree the 'one year heating off' analogy, at what point do the laws of physics not apply? one month? 1 week? one day, one hour?
    • lstar337
    • By lstar337 13th Oct 17, 9:57 AM
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    lstar337
    I have used this analogy many times on this forum.
    Originally posted by Cardew
    I know. I thought about putting a credit in for you.

    So if we agree the 'one year heating off' analogy, at what point do the laws of physics not apply? one month? 1 week? one day, one hour?
    Originally posted by Cardew
    • orrery
    • By orrery 13th Oct 17, 7:14 PM
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    • 444 Thanks
    orrery
    If your return temperature is increasing 'rapidly' then turn down the output until the return is low enough to keep it condensing. The return is only increasing because your rads can't shift the heat fast enough, or your house is already warm enough.
    Originally posted by lstar337
    No, I don't subscribe to the 'leave your heating on' notions.

    As for turning my boiler down, this is one of those "In theory, theory and practice are the same, but in practice they're not". Firstly, you need to keep the boiler temperature up to heat water above 60C, and to heat water (and the house) fast enough.

    In addition, the boiler behaviour may not be quite what you imagine. If the flow is set to 60C, then typically the return is 40C (on mine at least) which is fine. As TRVs start to close, the flow is restricted and the return temperature starts to increase - eventually the boiler modulates to hold the flow to 60C until it hits the maximum modulation (about 5kW on mine) - at this point the boiler allows an over-temperature of 7 degrees i.e. 67C flow, about 57C return and then shuts down. Far better to have the boiler flow temperature at about 68C, giving more rapid response to heating demand and allow the controller to manage affairs using proportional control. With proportional control, the maximum on time is about 45 minutes and it takes about 40 minutes for the boiler to reach 68C flow, which will be 48C return at full power which is fine, and is a far better all round strategy for economic running., but this will obviously depend on how clever your controller is.

    All in all, I find turning the boiler down to be least effective strategy.
    4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TL, SolarImmersion
    Location: Bedford, Roof: South East facing, 20 degree pitch
    Nissan Leaf, TADO Central Heating control
    • Richie-from-the-Boro
    • By Richie-from-the-Boro 13th Oct 17, 10:22 PM
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    Richie-from-the-Boro
    Quite right, thank you. That is why I want more discussion on efficient use of renewables.
    Originally posted by sue1201
    Which part of reliable renewable's produce constant base load grid-managed power is efficient ?
    Disclaimer : Everything I write on this forum is my opinion. I try to be an even-handed poster and accept that you at times may not agree with these opinions or how I choose to express them, this is not my problem. The Disabled : If years cannot be added to their lives, at least life can be added to their years - Alf Morris - ℜ
    • orrery
    • By orrery 14th Oct 17, 5:52 PM
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    • 444 Thanks
    orrery
    Which part of reliable renewable's produce constant base load grid-managed power is efficient ?
    Originally posted by Richie-from-the-Boro
    A bit off topic for this forum, but grid level or home batteries charged from renewables (solar, wind, biomass - whatever is plentiful at the time) would be extremely efficient. We know from studies conducted in Germany that we could make the switch to entirely renewables if we get our ourselves into gear.
    4kWp, Panels: 16 Hyundai HIS250MG, Inverter: SMA Sunny Boy 4000TL, SolarImmersion
    Location: Bedford, Roof: South East facing, 20 degree pitch
    Nissan Leaf, TADO Central Heating control
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