Heating water tank

  • HenryR's Avatar
    Level 1
    Should you leave the gas heating of your water tank on constant or timed to save on energy.
    Last edited by DebF_EONNext; 16-09-23 at 08:07. Reason: remove featured thread
  • 14 Replies

  • Best Answer

    theunknowntech's Avatar
    Level 79
    Best Answer
    Hey @HenryR !

    To be honest, the answer really depends on how well insulated the tank is. If you've got really good insulation, timed should be fine as most decent tanks have enough insulation to last for several hours, but if yours doesn't have that, you'll probably find the hot water runs out of heat pretty fast. Try timed for now and see how you go.

    As for central heating... Timed is probably OK as long as you can maintain a comfortable temperature.
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  • Han_EONNext's Avatar
    Community Team
    That really is a great explanation @theunknowntech - if I'm honest I'm not really too sure about the facts and figures!
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  • meldrewreborn's Avatar
    Level 91

    just like a house, the warmer the tank is, the the more heat it will loose which you then pay to replace. Timed is better financially so long as the tank holds enough hot water to cover your needs to the next timed period. I have an early morning on, an early evening on and the rest of the time its off. Obviously its different if you have a combi, but even then having hot water constantly available has a cost implication.

    Note my solar panel does the heavy lifting now, but this regime is still used in the winter when the solar contributes virtually nothing.
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  • wizzo227's Avatar
    Level 21
    It is summer time. For at least five days of every week, my combi gas boiler is OFF, really off; no central heating pump, no annoying whirring sounds, and no useless extra bit on the bills. On bath day, I do plan ahead to switch it on before needing a bathful, I usually run a sinkful and do 'large washing up' while the bath fills, and as soon as that is done I switch it back off for the rest of the week. For 'small washing up', or morning washing at the bathroom sink, a kettlefull of hot water is more economical than firing up the Normally OFF gas boiler, and that would be so even if I were not getting free electricity off the solar panels because at this time of year, heating the length of the pipe runs before any hot comes out is wasted heat.

    I suggest that you could get everyone in your household together to have a policy discussion about how many days per week should be 'bath days' (or hot shower) and switch it right off after last bath on bath night for more than a day. Investment and use of one ordinary kettle kept upstairs to top up warmth out of the hot water tap should cost a lot less than you save from forgoing hot tap water at times, and mostly avoids losses to heating the pipe runs up and down the house. When the weather gets colder in Autumn, such pipe losses go to warming the whole house hence needing central heating less, so you should decide in advance your criteria to go back to winter rules with more heating than at this time of year.
  • DebF_EONNext's Avatar
    Community Team
    Just thought I would weigh in on this one! Well actually My Grandad! He is 90, a retired engineer who worked on oil rigs and powers stations most of his life so runs experiments just for fun, or to drive me mad either or 🤔

    He ran an experiment recently. Over a 1 month period (during winter) he tested 4 different scenarios for 1 week each adjusting temperatures and frequency etc, measuring his output every day in the morning, afternoon then late evening at the same time everyday (to check for spikes apparently 🤷‍♀️)

    He said that he found there wasn't much of an energy or monetary saving (in his words it was minimal) between having the heating set very low constantly, to having it on for shorter blasts throughout the day. He said the energy he had saved having it switched off ended up being used to heat the pipes/radiators again once they had cooled.

    He lives in a Georgian property with high ceilings & thick stone walls, his boiler was replaced around 2 years ago so I would imagine it would be fairly efficient so I don't know if that makes any difference at all to his results 🤷‍♀️ I also realise this thread is about water but along the same lines and I found it quite interesting!
    Last edited by DebF_EONNext; 07-08-23 at 08:57.
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  • wizzo227's Avatar
    Level 21
    In summer, gas boiler OFF except for a few minutes per week is certainly saving gas bills by comparison to constant low. The 7kWh per week of electricity used by a central heating pump is also almost entirely saved.

    Your description of the 90 year old engineer findings sounds fair for 'winter rules' conditions; where the effort to warm up long pipe runs and old Geogian walls and so on starts to look big by comparison to the heat which comes out at the hot tap upstairs. In winter, if depending on gas central heating, any heat is useful heat. He is 90 so big spending to not be so dependent on gas imports next winter probably won't be in his priorities. Other suggestions to decrease his share of the heating bill include : if redecorating any rooms, add 2 inch insulation slab inside any exterior-facing wall before painting or wallpapering over. Consider splitting the bills with a lodger, as that sort of house is sure to have more exterior surface and less insulation than mine, so might not suit the heating spending of one person. Try telling him about the upstairs kettle. It does not have to be a brand new one, and if he can leave the gas boiler Off for a couple of days until bath day then he might save nearly as much CO_2 and money as I do.

    I'm presently on 'summer rules'. The boiler log shows 9125 seconds (about 3 hours) of elapsed usage since the start of April, mostly as several minutes on-while-filling the bath and then Off for a couple of days. Last week on one day I used it for an extra 15 minutes in five bursts which was enough central heating for the gloomiest day at this time of year. Morning wash by default uses a half kettleful of water costing 0.1kWh of energy; equivalent to about 22 seconds of gas boiler burn; 0.1kWh is not enough to warm the circulation within the combi gas boiler let alone the pipe run to upstairs, so it is not always worth burning any gas at all.
    Last edited by wizzo227; 09-08-23 at 13:00. Reason: to get clearer emphasis in first line
  • geoffers's Avatar
    Level 29
    TBQH: For the past year I've not bothered with the hot water, summer or winter. I've got an electric shower; dish washer maybe every 3rd day; can boil a kettle for washing up etc etc

    Seems daft to keep the tank hot 24/7 for just a few minutes of convenience per day.

    If i want a bit of luxury ie a hot bath after a cold bike ride for instance, I can get the tank from zero to hot in ½hr with both gas boiler & 3kW immersion heater: that may cost say 60p or so, but I bet that's cheaper than running it all the time.
  • meldrewreborn's Avatar
    Level 91

    I have a solar thermal panel so although my boiler is on in the summer months it only operates on cloudy days when insufficient radiation has reached the panels. In the period April to September my gas usage is down 2,700 kwh compared to pre panel times.

    At current prices that's worth about £200.. The period covers 183 days so its about £1.10 per day.

    Gas per kWh is about 20% of the electricity price (so electricity is 5 times the gas price) In the summer the equation could work out similarly as there are no heat losses from tanks or pipes. Whether the inconvenience is worth it is a matter of opinion.

    In the winter though, as has been pointed out, those heat losses go into the home and reduces the need (a little) for central heating. In the winter your regime is costing you money, not saving it.
  • meldrewreborn's Avatar
    Level 91

    When you heat your home you are essentially replacing the heat that has escaped through the fabric of the building. The higher the temperature inside the more heat that will escape and have to be replaced (at great cost). Hence why shutting the heating off during sleeping times and when you're out is so sensible. My thermostat has six time periods with different target temperatures across 24 hours and for each day. I also have thermostatic valves setting different temperatures for different rooms - bedroom have different temperatures (lower) than more occupied rooms.

    Having the heating on constantly will use more energy than having shorter on bursts because the average temperature in the home will be a tad lower. QED.

    Its also why loft, wall and floor insulation, double glazing, draught prevention etc save money because that expensive heat you loose doesn't need to be replaced so much.
    Last edited by meldrewreborn; 18-08-23 at 10:20.