Air source heat pumps in winter: Busting the myth

  • retrotecchie's Avatar
    Level 92
    @meldrewreborn

    Just for fun, I ran an effective tariff rate calculation on my 21-22 consumption figures. Depending on how much electricity I used and when, my effective tariff rate varied from 24.91p a unit on higher consumption days (laundry and/or cooking) to 42.95p a unit on hot summer line drying and salad eating days.

    No practical use for the data as it stands just yet but it certainly makes for an interesting interpretation of my energy use.

    The min and max ETR for 22-23 was 29.7p and 43p respectively. Infer from that what you will Name:  confused.gif
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    Last edited by retrotecchie; 04-01-24 at 20:00.
    Don't shoot me, I'm only the piano player. I DON'T work for or on behalf of EON.Next, but am willing to try and help if I can. Not on mains gas, mobile network or mains drainage. House heated almost entirely by baby dragons.
  • wizzo227's Avatar
    Level 21
    Standing charge is another reason to dislike pennies for a unit to discuss energy saving.
    @wizzo227
    if the only thing you are using the gas combi for is to heat your bath water, you have to add your standing charges on to the cost of that bath. With a standing charge around the 30p a day mark, that makes each bath cost about £1.35.
    That is another reason to prefer electric-only hot water.

    A while back, there was a company called Ebico who did gas at nil standing charge, so it is not that it can't be done.

    Allowing ten years of inflation at government target 2.0% APR compounded from 2014 standing charge, by how much are all the energy companies overcharging everyone for standing charge ?
  • retrotecchie's Avatar
    Level 92
    @wizzo227

    Funnily enough, they are no longer trading as an energy supplier. OVO, on the other hand, are still in the game, and they originally started with tariffs that had no standing charges. Clearly either the model no longer works, or OFGEM doesn't allow it. One or t'other.

    The root of energy saving is to simply use less energy. But the energy you do use has to have a monetary value in order to pay for it. TANSTAAFL.

    Last edited by retrotecchie; 04-01-24 at 20:55.
  • wizzo227's Avatar
    Level 21
    The electrical energy off my roof is literally free of cost. Even the capital cost of all that solar photovoltaic hardware plus nominal interest from self to self is all repaid and done. Miserly kettle baths and a life in sackcloth and clogs is not what I wish for everyone else. It is that the hindrances preventing enduring renewable energy installation be removed for almost everyone, until quite good living standards become obtainable without ever buying or causing anyone else to buy polluting fossil fuel.
  • meldrewreborn's Avatar
    Level 91
    @wizzo227

    Companies that charged little or no standing charges usually had a two tier approach to unit prices. The first x unit per period were at a high rate that recovered the unit charges, then the remainder were at the normal rate ( the same as if standing charges had been levied).

    OFGEM do not prohibit such tariffs today, it’s why their limitation through the price caps apply at certain consumption thresholds - 3,100 kWH for electricity and 12,000 for gas. Suppliers are allowed to play tunes with their offerings so long as they do not exceed the maximum charges when the thresholds are reached. Competition pressures work to prevent the companies playing such tunes. Of course the price caps don’t apply to fixed tariffs so they could tinker to their hearts content on those by lowering or removing standing charges to the end consumer, but internally they would still be paying such charges to the rest of the industry

    The lower ones consumption is, the more significant standing charges become in bills. Inevitability this influences opinions.
    Current Eon Next customer, ex EDF, Zog and Symbio. Don't think dual fuel saves money and don't like smart meters. Chronologically Gifted. If I offend let me know by private message, but I’ll continue to express my opinions nonetheless.
  • wizzo227's Avatar
    Level 21
    @wizzo227
    The lower ones consumption is, the more significant standing charges become in bills.
    Yes. It is not really worth paying for all that gas pipeline and expensive work digging up the street because for a long term survivable CO_2 per person per year we can't just burn fossil gas in any quantity like last year, and the quantity which we can afford to burn isn't worth the standing charge. The sooner it only gets made into high value polypropylene and suchlike durable goods the better.
  • wizzo227's Avatar
    Level 21
    The exact kWh of .204 cubic meters of gas for todays' bath will slightly depend on a calorific value in the next gas bill.
    @wizzo227
    50 litres of water from tap (approx 10°C) to boiling is 90°C change x 50kg x 4200 Joules of energy, or 18.9MJ. That is equal to 5.25kWh but at an efficiency of 86% you would need nearer 6.1kWh of gas, not allowing for temperature losses in the pipe. So nearer 7kWh, most likely.
    So if you heated your bathwater to 55°C, that's half the energy. Call it 3.5kWh, or about 31p worth of gas.
    I was so annoyed about seeing the 3.5kWh figure for a bath where I'd claimed 2kWh that in case I might be mistaken I decided to go outside and look at the gas meter before and after filling todays' bath.
    In units of cubic meters,
    before : xxxxx.118
    -after : xxxxx.322
    Bath was filled to 10cm depth at the deep end, temperature in the mid 40's of C.
    In case you are wondering how I used less gas than expected, I did a couple of hacks.
    The house central heating was used for 9 minutes beforehand, using as much gas as the bath fill. That was to mitigate the long warm up time of the combi boiler. The combi boiler circulation was then allowed to settle, which got to 30C at both boiler outlet pipe and house central heating return pipes.
    Gas burn was started on a timer; 9 minutes ON. Upstairs hot tap was opened minimally to select the heat exchanger path at the diverter, until warmth reached upstairs, and then the bath tap was opened more. A moderate boiler outlet temperature, believed to be about 65C circulation within the combi boiler, provided heat to the heat exchanger plate as is usual in combi gas boilers, while mains inlet cold went through that heat exchanger to the "hot" pipe to upstairs, which takes a while to warm up.
    Gas burn was switched off by timer more than a minute before the hot tap upstairs was turned off, recovering about half of the heat in the 10 metre pipe run to upstairs.
    The on-demand gas throttle, which is the bit which gets triggered by hot water demand and doubles your gas consumption and blows steam out of the flue while you shower, was disabled.
    Last edited by wizzo227; 05-01-24 at 14:54.
  • meldrewreborn's Avatar
    Level 91
    It would be better to turn off gas generated electricity - its the most expensive fuel source and keeps the prices paid for electricity generated by the other fuels almost as high. Coal generation with CO2 capture is a better solution - and less expensive - but try telling that to the eco brigade.
  • meldrewreborn's Avatar
    Level 91
    The exact kWh of .204 cubic meters of gas for todays' bath will slightly depend on a calorific value in the next gas bill.

    I was so annoyed about seeing the 3.5kWh figure for a bath where I'd claimed 2kWh that in case I might be mistaken I decided to go outside and look at the gas meter before and after filling todays' bath.
    In units of cubic meters,
    before : xxxxx.118
    -after : xxxxx.322
    Bath was filled to 10cm depth at the deep end, temperature in the mid 40's of C.
    In case you are wondering how I used less gas than expected, I did a couple of hacks.
    The house central heating was used for 9 minutes beforehand, using as much gas as the bath fill. That was to mitigate the long warm up time of the combi boiler. The combi boiler circulation was then allowed to settle, which got to 30C at both boiler outlet pipe and house central heating return pipes.
    Gas burn was started on a timer; 9 minutes ON. Upstairs hot tap was opened minimally to select the heat exchanger path at the diverter, until warmth reached upstairs, and then the bath tap was opened more. A moderate boiler outlet temperature, believed to be about 65C circulation within the combi boiler, provided heat to the heat exchanger plate as is usual in combi gas boilers, while mains inlet cold went through that heat exchanger to the "hot" pipe to upstairs, which takes a while to warm up.
    Gas burn was switched off by timer more than a minute before the hot tap upstairs was turned off, recovering about half of the heat in the 10 metre pipe run to upstairs.
    The on-demand gas throttle, which is the bit which gets triggered by hot water demand and doubles your gas consumption and blows steam out of the flue while you shower, was disabled.

    I just turn the tap on. But my last bath was some years ago when i had some stiches to dissolve!

    In my youth a bath was one a week event, and I'd wash from a sink on other days. Still its difficult to stop progress!!
  • meldrewreborn's Avatar
    Level 91
    I would add that quantifying the cost of water heating separate from space heating is a task that needs a great deal of instrumentation if it is to be done with accuracy.

    consequently we just gloss over it.