Posted by: @jamespetts

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Latest data.

Monday: heating running all day, outdoor temperature 11.5C, heat curve 0.6, 3.3kWh consumed.

Tuesday: heating off between circa 1200h and circa 1900h, outdoor temperature 11.3C, heat curve 0.55, 2.7kWh consumed.

Something else to consider now you’re starting to capture data is to make a note of your internal air temperature. You’re leaving an hour in the evening for your heat pump to heat the house back up; have you checked it has managed that by the time you get back home? If it has, could you delay the startup a bit later and save more energy? If not, and you need to start the reheating earlier to get up to temperature when you walk through the door, how do the consumption figures look then?

Also, if you’re on a time of use tariff, well worth tracking the leccy price at the time the heat pump is consuming it. Today, for instance, import prices for me are about 25p for most of the day, but the 4pm-7pm stretch varies between 55p and 71p. Not great saving 1kWh during the day by buying half a kWh during the evening at almost triple the price.

As @editor said, the decision about best strategy must be yours and this forum’s goal is to help equip you with the understanding necessary to make that choice. The factors feeding into it are more complex than first appears and that historical record of observed data is invaluable.

Posted by: @majordennisbloodnok

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@jamespetts, there are plenty of threads on this forum basically saying that observation will trump theory every time so I applaud your inclination to test.

I will say, however, that just one observation during a temperate period is not in itself enough to go on, especially when the observed difference is a single kWh. I would strongly urge you to carry out several more of these tests to average out for this kind of mild weather and then several more in the depths of winter when the heat pump's performance may be different. You may find your assumptions change, you may find they are even more strongly vindicated.

When it comes to comfort and recovery I totally agree. But you did use the word Trump which did make me shiver quite a bit this morning. 🤡

I am aware of the significance of not asking for a high heat demand in the 1600h - 1900h period, and so try to return home after this where possible. One of the reasons that I did not work from home yesterday was precisely the very high electricity prices, so the point was to be away from home and not have the heating running during that time to avoid them.

I did check the internal air temperature on the Underground home yesterday and found that it had reached 20.5C when I was about 2/3rds of the way home (very approximately). However, it likely to be impossibly difficult to remember to turn the heating on at a specific point in the journey home in future, and, in any event, it will take longer to reach the desired temperature when the weather is colder.

In any event, I will continue to post figures here to monitor the situation and to accumulate data.

Agreed, @jamespetts. I don't know the Vaillant app or any other control system you have to hand, but is it possible to easily set a scheduled turn-on? i.e. when you're about to leave tell the system to come on in half an hour's time? All part of the playing around with a new install, from what I remember.

What tariff are you on, btw? And do you have any other electric equipment that might significantly affect the choice of tariff and/or ideal times to import power such as an EV, solar PV or a battery? 

Latest data: 6 November 2024; heating running all day; 3.7kWh heating demand; outdoor temperature average 10.5C; heat curve lowered from 5.5 to 5.0 during the day.

Setting a temporary schedule is not straightforward in the Vaillant app - one would have to edit the permanent schedule then remember to set it back again, which is not practical.

I have solar PV, but no EV or battery, albeit I am considering getting a battery in the future.

Posted by: @jamespetts

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Latest data: 6 November 2024; heating running all day; 3.7kWh heating demand; outdoor temperature average 10.5C; heat curve lowered from 5.5 to 5.0 during the day.

Setting a temporary schedule is not straightforward in the Vaillant app - one would have to edit the permanent schedule then remember to set it back again, which is not practical.

3.5kWh spread over 24hrs is only 150W.  Do you mean that?  If so Id stop worrying about a kWh here and there, its so low.

Posted by: @jamespa

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Posted by: @jamespetts

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Latest data: 6 November 2024; heating running all day; 3.7kWh heating demand; outdoor temperature average 10.5C; heat curve lowered from 5.5 to 5.0 during the day.

Setting a temporary schedule is not straightforward in the Vaillant app - one would have to edit the permanent schedule then remember to set it back again, which is not practical.

3.5kWh spread over 24hrs is only 150W.  Do you mean that?  If so Id stop worrying about a kWh here and there, its so low.

 

Yes, 3.7kWh was the total space heating consumption yesterday according to the MyVaillant app. Is that low?

Total electricity demand yesterday overall according to my solar app was 15.2kWh, of which 13.7kWh were imported. Yesterday's electricity consumption other than space heating from the Vaillant heat pump included cooking dinner, hot water production, base load, running a desktop computer and space heating in the shed, which has a totally independent air-air ASHP (which also does cooling in the summer).

Posted by: @jamespetts

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Yes, 3.7kWh was the total space heating consumption yesterday according to the MyVaillant app. Is that low?

Well yes. 

It will cost you <£1.  Divide by 24 to get power as opposed to energy, and you get 150W.  That's one and a half 'old' electric bulbs, and one third of the average TOTAL electrical consumption of a typical UK house (excluding heating).  You will be spending more on the electrical items you leave on, your fridge etc, plus any washing machine, TV etc.

Put another way, even at a COP of (say) 5, thats only 750W to the house, one half to one third the output of a hair drier - to heat your house.

Probably worth checking what your electricity meter is reading to be certain, remembering of course that the heat pump is not the only load.

I presume your house is well insulated etc.  At this level I wouldn't bother with fiddling too much with schedules to the nearest hour.  A broad brush approach (but still dialling down the heat curve until its as low as it can go whilst keeping the house warm) is likely to be good enough.  Obviously its up to you but sometimes its worth getting things in proportion.

BTW if this is typical I think its unlikely that you will make a business case for a battery work and the jury is still out on whether price optimisation using local storage is green or not (because the correlation between electricity price and carbon intensity is rather weak).

Interesting. It is still worth turning the heating off when I go out for the same reason that it would be worth turning a 100W bulb off when I go out. What is a more typical space heating usage for a two bedroom terraced house?

My house is not especially well insulated. It is a 1909 build terraced house. The loft is insulated and I have double glazing (recently replaced with the latest standard at the rear of the house - but not the front), except in one small window in the kitchen. The walls are solid brick.

However, what I do have is a Honeywell EvoHome system with automatic TRVs. I have this set only to heat the rooms that I typically use. Many people, including the installers, seem to be of the view that this reduces efficiency, which it might if measured only in terms of COP, but I suspect that there may be an erroneous focus on COP rather than minimising power usage overall without being too cold. If (as I am increasingly suspecting might be the case), the highest COP can only be achieved at higher heat outputs (and therefore energy inputs), then this may well lead to sub-optimal system design and usage. To put this into perspective, the COP yesterday recorded by the MyVaillant app was only 3.2, with energy consumption of 3.7kWh and 11.9kWh of heat generated. Even if I could have had a COP of 4 generating more than 11.9kWh of heat, that would be of no benefit to me, as I was perfectly comfortable with the amount of heat that I actually generated.

@jamespetts I would dare say that at least 75% of heat pump owners would be extremely pleased to have so low a consumption and the comfort level you require!

As to your question: It is still worth turning the heating off when I go out for the same reason that it would be worth turning a 100W bulb off when I go out.

Turning off lights (unless for security purposes) makes a lot of sense as the energy consumed in your absence is an absolute waste - it has gone without any benefit other than a small amount of heat [particularly if you are using LED lights] whereas, the heating residual will more than likely give some benefit; if well insulated, thus little loss, I think that leaving the heating on would likely be a plus point! Your mileage may vary but that would be my view. Regards, Toodles.

Iv got an 8.5Kw Ecodan and my testing shows a saving of approximately 5Kwh £1.30 per day by prohibiting heating during the hrs of between 2300hrs- 0445hrs and 0700hrs- 1545hrs.

H/w heating between 0345hrs-0700hrs only.

my low rate electricity is between midnight and 7am.

Heating set at 20 degrees 

with an outside temperature of 11 degrees.

TBH I’m still undecided if it’s worth while.

COP is 3.2 on all day

COP is 2.9 when staggering.

Posted by: @jamespetts

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My house is not especially well insulated. It is a 1909 build terraced house. The loft is insulated and I have double glazing (recently replaced with the latest standard at the rear of the house - but not the front), except in one small window in the kitchen. The walls are solid brick

That may be the key.  Terraced houses, even more so flats, benefit from being adjacent to heated spaces.  If you shut off heating to rooms you don't use the most likely effect is that you 'rob' heat from your neighbours, a factor that installers are unlikely to take into account.

What, as a matter of interest is the floor area?  12kWh/day still seems low at an OAT of 10, but if you add to this say a further 10kWh from your appliances (based on the average electricity consumption of 3.6MWh/year and the reasonable assumption that all the energy eventually ends up as heat)) and perhaps 1kWh from you, not unbelievable.