Dimplex Quantum storage heaters / Octopus Go Faster tariff

Here's an interesting (depending on your definition of interesting) factoid.  Dimplex state:

Most Dimplex storage heaters can fully charge within 5 hours and the automatic charge calculation may not always take a full charge . .

This is significant as it implies that anyone with properly-spec'd Quantum heaters can swap over to Octopus's Go Faster tariff (subject to it being offered to them, apparently, and them having a suitable smart meter) and still be able to take a full charge, but with much lower off-peak and on-peak unit costs.  This is a bit of a game-changer as the general assumption seems to be that NSHs require their full available off-peak time to store the maximum charge.

Since the newer Lot-20 compliant NSHs can hold onto more heat for longer, the extended interval between charges also shouldn't be an issue, provided the combination of stored charge and perhaps use of direct heaters in the off-peak hours, can meet the dwelling's space heating demand.  Perhaps other manufacturers' NSHs also can take a full charge in five hours.

Since the tariff isn't guaranteed to continue into the future, you wouldn't want to base any big decisions on it, but for households already kitted out with high-heat retention NSHs, it's worth considering for the near term

Comments

  • matelodave
    matelodave Posts: 9,017 Forumite
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    edited 13 September 2021 at 9:25AM
    I think you'd have to do some clever sums to ensure that you get sufficient heat stored during the charging period to satisfy the heat demand over the discharge period otherwsie you could find that you are using the boost/back-up heater on peak rate rate leccy to cover the shortfall and lot more than you'd hope.

    Not saying that it cant be done but I'd suggest that it requires careful heatloss calculations rather than the "wet finger in the air" guesses than most people make if you want to avoid making a costly mistake.

    The amount of charge the heater can take is direclty related to it's storgage capacity and the rating of the element so a 3kw elelemt for seven hours = 21kwh, if you only have 5 hours at cheap rate then it can only store 15kwh despite it's storaage capacity. Although if you assume that there might be some heat still stored, say 5-6kwh, it's feasible that you could top it up to 21kwh within 5 hours, but if it's been cold or you've used boost then you wont fully recharge it. I'd guess that more than a couple of days of cold weather would leave you short of stored heat, requiring peak rate boosts to keep warm
    Never under estimate the power of stupid people in large numbers
  • coffeehound
    coffeehound Posts: 5,741 Forumite
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    edited 17 September 2021 at 3:54PM
    Thanks for your input, @matelodave.  As you say, the NSH cannot take in higher charge than its instantaneous rating allows, so I wonder if this is down to loose English usage and what it should have said is "most Quantum NSHs, in most situations, for most of the year, can achieve the required charge within 5 hours."  Poor form in a technical document if so.  I've asked Glen Dimplex tech services for clarification.

    This is then the same discussion as had in another thread recently:  if the NSH is charging to 70% or less during Economy 7 hours, then that same charge could be achieved with a higher charge duty-factor during the reduced 5-hour window (i.e. being switched-on more of the time during that period).   A good thing with a modern NSH is that you tell it the hours available, and it calculates how long it needs to take power for within that window.

    Honestly I think this can be treated more with the 'wet finger' approach.  The peak-time Octopus rate is comparable with single-rate tariffs, and the off-peak rate is about half that of typical Economy7 off-peak rates.  So the potential for savings is substantial.   Also Octopus do not charge exit fees, so if one really wanted to go elsewhere, it wouldn't be a problem.

    As to the 19 hour interval between charges, the number of hours of required heating each day remains the same.  Perhaps from midnight to 7am there is no heating requirement at all, in which case the NSHs just hold onto their charge.  The SAP calculations, which are intended to mirror the real world, take High Heat Retention NSHs as being capable of retaining 45% of the original heat charge after a full 24 hours.

    In the worst case scenario that there was not enough stored charge to last into the evening, then choosing a timing where for example the off-peak rate starts at 8.30pm gives the option to use direct electric heaters in the evening at off-peak rate.

    So really for high heat retention NSHs, the potential for savings is high, and the risk of higher costs is low.  

    It is the case of old-school NSHs where the decision becomes harder, as discussed in the other recent thread
  • Here's what GD say

    In regards to the charging, yes our heaters can in fact charge fully within 5 hours in most occasions but this does depend on the installation, size and some environmental factors so we do still advise having the economy 7/10 supply available, especially during the winter months when the demand for heat is higher.

  • I have a one bed house and have actually just done this and installed a Dimplex Quantum QM150 to use with the Octopus Go tariff. I’ve set it so it can only charge in the 00:30 – 04:00 time slot.

    It has several timers which are pre-programmed, but you can modify them to suit your situation better, for example In all day, Out all day and then one called Timer, which is fully customisable. Each timer can have 4 periods in a day.

    What it does is use these timers to evaluate how much of a charge it’s going to need to provide the required heat for the next day. For example, I can see on a day I set it to Out all Day, it used a lot less electricity than on a day I set the timer to In all day.

    It's early days, but my house is now nice warm despite the autumn chill, I'm looking forward to how things will work out in the winter.

    I think modern storage heaters get a bad press, but modern storage heaters will store energy from whatever time of the day or night you want it to, and from any source like solar. The original Economy7 tariff is probably on its way out, but is being replaced by smart time flexible tariffs that are focused on EVs. It would be great to see a storage heater automatically interact with Octopus’s Agile tariff, like some EV chargers do.

    I can also run the QM150 like those Fischer heaters, which are sort of meant to run 24/7 in the back ground. The difference is the Quantum will use the cheap 14Kw of heat it's stored before drawing any peak rate electricity.


  • Thanks for your post, @DebtFreeDream_2 , it’s very helpful to get real-world experience from owners. 

    I did ask GD if they planned to offer integration with Octopus for their cloud control platform, but they said there were no plans at present. Hopefully that will be the future where setting the correct timings is automated. 
  • Swipe
    Swipe Posts: 5,562 Forumite
    Part of the Furniture 1,000 Posts Photogenic Name Dropper
    I'm surprised you have your storage heaters on already but please keep us updated as winter approaches.
  • Swipe said:
    I'm surprised you have your storage heaters on already but please keep us updated as winter approaches.
    My wife wanted to put the heating on today as she felt cold.
    The temperature in the lounge was 19.3 deg C
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