EV Discussion thread

EricMears

Grumpy_chap said:

What are the methods that people use to shift large proportions of energy demand to the short night-time window benefitting from ToU cost savings?

I'm on 'Go-Faster' so have 5 hours from 9:30pm so it's perhaps easier for me than most.  However my son is on Go so I appreciate his problems.

EV charging time is fully set by car so it's pretty straightforward to arrange to use the off-peak window only.  My son's car only lets him delay the start time so I've advised him to try and charge before battery gets below half full which approximates to less than 4 hours needed.

Although main heating is by an oil boiler,  I also have an immersion heater in the 'Heatbank' which I tend to run in o/p window as well.

We start washing machine & dishwasher at 9:30 pm and sometimes stay up to start a second load at midnight.  Son 'starts' his around 9:30 but with a 3 hour delay set.  Neither of us use a tumble drier.

We often do some cooking after 9:30 but only to part-cook then only need reduced time next day.  Not an option for son (unless he's staying up till early hours for some reason).

Not a great deal else we can do at this time of year.  Roll on Summer when we can try and use solar power.

So far this month our % usage  is around 65% off peak (equiv to 17.4ppu) but we've been away for a few days so not using o/p power for car charging (but luckily had a Bonnet 'stockpile'); otherwise I'd probably have been able to report >70%

Update : After a couple more hours charging last night that's improved to 65.4% & 17.3ppu

michaels

Our house seems to run somewhere around 300w minimum.  Somehow by trying to avoid daytime usage via timeshift we do about 10kwh of our 20kwh daily between midnight and 5AM (our cheap window).

Our tariff is 4.5p/45p, in our region SVR is 34p so we save regardless of EV/Battery.

7,000 x .34 = 2,380.  3500 x 0.45 + 3500 x 0.045 = 1733 saves £647 pa



Gains from charging the car at 4.5p rather than 34p are on top - 29.5p x 3500kwh (12k miles at 3.5 miles per kwh after allowing for charging losses) = £1033

Battery means we also do the 10kwh day usage from overnight 4.5p electric; saving is 29.5p x 3500 units = £1033 less efficiency loss - say 20% so 700 units at 4.5p = £32 = £1000 saving but of course there is a capital cost.

Plus we run the immersion in the hot water tank so this is heated by 4.5p 100% efficiency electricity rather than 10.3p 85% efficient gas.  Say 8kwh per day saves about £200 per year

There are other savings from battery via maximising own use of solar - each kwh used instead of exported saves 34p (12p if it is just iBoost into the hot water tank) - Say 1500kwh x (34+12)/2 = £345

70sbudgie

I'm on E7 SVT which is cheaper for me than the latest Go tariff. Our base load is ~140W, so the extra 3 hours from E7 over Go more than makes up for the small difference in night rates. I think our annual night import is about 40% of total import. This is helped by PV for a lot of the year.

E7 also means I have a bigger window to do things like delay the washing machine start so it finishes just before 7am. I only run it on days when I will have time to hang it in the morning. The dishwasher is nearly always programmed to start after midnight. And again my EV is nearly always programmed to only charge during off peak. But I've already made the savings before taking into account charging the car. 

Martyn1981

Grumpy_chap said:

Petriix said:

Without much effort my home usage is ~ 40% off-peak 

What are the methods that people use to shift large proportions of energy demand to the short night-time window benefitting from ToU cost savings?

Hiya GC, we didn't shift to E7 till we got the BEV. It was close with PV, but our leccy consumption wasn't quite high enough to make it work.

But obviously with a BEV, a very high energy consumption item, that can be completely and easily charged on cheap rate it makes sense.

Also worth considering, perhaps, in these discussions how PV impacts E7. Cheap rate tariffs tend to come with a higher day rate, but PV will reduce consumption during those higher priced times, so helps to tip things in favour, but as I said, it wasn't quite enough for us initially.

Another possibility, as you mentioned space heating, is the use of an A2A heat pump (an A/C unit). We have two, and other PV'ers have done similar, to benefit from cheap heating during the shoulder months. But we also use ours overnight in the winter to help reduce GCH. The COP won't be as good in the night as the day, but 7hrs of relatively cheap heating is another potetial plus. 


Edit - Should have said, that all of these options support each other. So whilst PV and a BEV may suit most households, batteries, E7 and A2A may be trickier to justify, but I think each makes the case for the others stronger.

Not trying to cheat on the maths, but if PV and or a BEV justify E7, then a batt may make more sense, and also lead to A2A use during the day, on cheap rate. So the whole is greater than the sum of the parts. Hope that makes sense.

JKenH

Martyn1981 said:

Grumpy_chap said:

Petriix said:

Without much effort my home usage is ~ 40% off-peak 

What are the methods that people use to shift large proportions of energy demand to the short night-time window benefitting from ToU cost savings?

Hiya GC, we didn't shift to E7 till we got the BEV. It was close with PV, but our leccy consumption wasn't quite high enough to make it work.

But obviously with a BEV, a very high energy consumption item, that can be completely and easily charged on cheap rate it makes sense.

Also worth considering, perhaps, in these discussions how PV impacts E7. Cheap rate tariffs tend to come with a higher day rate, but PV will reduce consumption during those higher priced times, so helps to tip things in favour, but as I said, it wasn't quite enough for us initially.

Another possibility, as you mentioned space heating, is the use of an A2A heat pump (an A/C unit). We have two, and other PV'ers have done similar, to benefit from cheap heating during the shoulder months. But we also use ours overnight in the winter to help reduce GCH. The COP won't be as good in the night as the day, but 7hrs of relatively cheap heating is another potetial plus. 

Yes, I have 2 wall mounted ASHPs and I have in previous years run them overnight often averaging only around 200watts(each) over 24 hours. I found though that when I most needed them (in cold weather) they were at their least efficient so haven’t bothered lately.  If you have a traditionally built house with block work walls you can use them to raise/maintain the core temperature overnight but at the moment I find I get more benefit just putting them on for a blast to heat the room up quickly when I need it. Having said that I leave the living room one on all day 9am to 3.30pm to make use of what little PV we have this time of year. It goes off when the CH comes on then when the CH goes off at 6.40pm I will put it back on if needed if we are using that room. If it is cold outside we go in the setting room and have a log fire.

Petriix

JKenH said:

Petriix said:

Let's be absolutely clear. At 40p/12p you'd only have to shift ~ 20% of your home usage into the off-peak window before your saving money vs the cap price.

To somehow twist this money saving opportunity into a hidden expense is, at best, willful ignorance. 

Octopus Go

1000kWh @ 12p = £120
4000kWh @ 40p = £1600
total 5000kWh = £1720 or 34.4p

SVT

5000kWh @ 33p/kWh = £1650

so it is £70 cheaper to be on the SVT. 

The important point though is what is the effective rate you are paying for your off peak compared to SVT?

£1720 is equivalent of paying for 4000kWh @ 33p (SVT ) = £1320 plus 1000kWh @40p= £400

If you were on SVT you would pay a flat rate of 33p for all your usage but for the 80/20 user being on Octopus Go means you are paying the equivalent of 33p for peak usage and 40p/kWh for your off peak usage. 

I'm sorry, but you're nitpicking over a few percent (depending on your region). The point is that, with minimal effort, you can break even and, with a bit more dedication, you can save money on your domestic usage before you even consider the enormous savings on car charging.

The other massive consideration is that Go is fixed (with no exit fees) so you can always jump to a cheaper tariff if one pops up, but you're not at the mercy of government policy changes in regards to the price cap.

If I were paying current Go prices this year my total usage (ex standing charge) would have been £671.28. On the current price cap it would have been £1177.05. 

JKenH

Petriix said:

JKenH said:

Petriix said:

Let's be absolutely clear. At 40p/12p you'd only have to shift ~ 20% of your home usage into the off-peak window before your saving money vs the cap price.

To somehow twist this money saving opportunity into a hidden expense is, at best, willful ignorance. 

Octopus Go

1000kWh @ 12p = £120
4000kWh @ 40p = £1600
total 5000kWh = £1720 or 34.4p

SVT

5000kWh @ 33p/kWh = £1650

so it is £70 cheaper to be on the SVT. 

The important point though is what is the effective rate you are paying for your off peak compared to SVT?

£1720 is equivalent of paying for 4000kWh @ 33p (SVT ) = £1320 plus 1000kWh @40p= £400

If you were on SVT you would pay a flat rate of 33p for all your usage but for the 80/20 user being on Octopus Go means you are paying the equivalent of 33p for peak usage and 40p/kWh for your off peak usage. 

I'm sorry, but you're nitpicking over a few percent (depending on your region). The point is that, with minimal effort, you can break even and, with a bit more dedication, you can save money on your domestic usage before you even consider the enormous savings on car charging.

The other massive consideration is that Go is fixed (with no exit fees) so you can always jump to a cheaper tariff if one pops up, but you're not at the mercy of government policy changes in regards to the price cap.

If I were paying current Go prices this year my total usage (ex standing charge) would have been £671.28. On the current price cap it would have been £1177.05. 

Can I just wind back a couple of pages and remind you what the subject of my post that started this discussion was - in case you have forgotten

Let’s be honest about how much charging your car on Octopus Go actually costs.

The argument is not that Octopus Go is a bad tariff - it is that most people claim that it only costs them 5, 7.5 or 12p/kWh to charge their car without taking into account they are paying more than a standard variable tariff for their peak time usage. How many times do we hear, not just on this forum but elsewhere, when comparing the cost with ICEs that “it only costs me 5p/kWh to charge my EV”. I doubt many people on Octopus Go, when faced with a dyed in the wool ICE driver challenging your choice to drive an EV, are able to resist slipping it in to the discussion. I admit I have in the past. 

Perhaps @michaels could legitimately claim that, as he/she has virtually no usage outside off peak rates, but for most of us and certainly most new EV owners that will not be the case. I am perfectly willing to acknowledge that for some, even most, current EV owners Octopus Go works well and is cheaper overall than a standard tariff. If you don’t modify the rest of your electricity consumption, then the cost per kWh by comparison to a standard tariff is nowhere near the headline rate 5/7.5/12p rate quoted. If anyone thinks it is, then @michaels and possibly one or two other enthusiastic energy savers excepted, you haven’t thought it through or you are deliberately trying to mislead.

Now in relation to your specific comments in your last post about nit-picking I would point out that I used an average rate of 33p/kWh. This for some reason offends you. Below are the regional rates. 10 regions are below 33p and 4 regions above it. In fact 5 of the regions are below 32p. Maybe it’s 34 p where you live but it’s 31.4p where I live but I didn’t quote my rate, I quoted 33p. 

Now just to demonstrate I was focussing on the impact of peak usage on the effective off peak rate quoted, rather than being anti EV I did not adjust for charging losses, which, in the case of my Leaf, varied but were of the order of 15%. When I told @Exiled_Tyke his/her real charging rate was 15p I should also have said that each kWh that actually goes into the car is costing in the region of 17p.

Edit: in case no one else has noticed it these figures are ex VAT so perhaps I am being hard on you. 34p incl VAT is perhaps more realistic as an average. (9 regions below 34p incl Vat  (32.38p ex Vat) and 5 above). Apologies. 

Petriix

I get what you're saying: people might pay more for their domestic usage on Go; if they didn't bother to load-shift into the off-peak window. However, you seem to be presenting that as an automatic down-side whereas I see it as an opportunity to save money. The more effort you put in, the more you save!

It turns out it's closer to 30% required to break even at current Go prices in my region because the latest peak rate is 44.45p, but my point still stands. As ever with such things, rather than making a blanket assumption that people will be worse (or better) off, it pays to do a reasonable calculation based on actual (and potential) usage.

I appreciate that not everyone has access to precise data. Because I can access both the Octopus and Myenergi APIs I have a uniquely detailed analysis of my own usage and can see exactly how much peak/off-peak/solar energy is going into the house and the car. Being on Go has saved me hundreds of pounds vs being on the standard rate and a significant chunk of that is my home usage.

You're right that I've used the '5p per kWh' line and even '1.25p per mile' which are both true for me, and unobtainable for new EV owners. But I tend to qualify it now with 'and at current prices it's more like 3p per mile'; and those figures do include charging losses.

JKenH

Petriix said:

I get what you're saying: people might pay more for their domestic usage on Go; if they didn't bother to load-shift into the off-peak window. However, you seem to be presenting that as an automatic down-side whereas I see it as an opportunity to save money. The more effort you put in, the more you save!

It turns out it's closer to 30% required to break even at current Go prices in my region because the latest peak rate is 44.45p, but my point still stands. As ever with such things, rather than making a blanket assumption that people will be worse (or better) off, it pays to do a reasonable calculation based on actual (and potential) usage.

I appreciate that not everyone has access to precise data. Because I can access both the Octopus and Myenergi APIs I have a uniquely detailed analysis of my own usage and can see exactly how much peak/off-peak/solar energy is going into the house and the car. Being on Go has saved me hundreds of pounds vs being on the standard rate and a significant chunk of that is my home usage.

You're right that I've used the '5p per kWh' line and even '1.25p per mile' which are both true for me, and unobtainable for new EV owners. But I tend to qualify it now with 'and at current prices it's more like 3p per mile'; and those figures do include charging losses.

OK, we both understand where the other is coming from so I am happy to park our discussion here. 

shinytop

JKenH said:

Petriix said:

I get what you're saying: people might pay more for their domestic usage on Go; if they didn't bother to load-shift into the off-peak window. However, you seem to be presenting that as an automatic down-side whereas I see it as an opportunity to save money. The more effort you put in, the more you save!

It turns out it's closer to 30% required to break even at current Go prices in my region because the latest peak rate is 44.45p, but my point still stands. As ever with such things, rather than making a blanket assumption that people will be worse (or better) off, it pays to do a reasonable calculation based on actual (and potential) usage.

I appreciate that not everyone has access to precise data. Because I can access both the Octopus and Myenergi APIs I have a uniquely detailed analysis of my own usage and can see exactly how much peak/off-peak/solar energy is going into the house and the car. Being on Go has saved me hundreds of pounds vs being on the standard rate and a significant chunk of that is my home usage.

You're right that I've used the '5p per kWh' line and even '1.25p per mile' which are both true for me, and unobtainable for new EV owners. But I tend to qualify it now with 'and at current prices it's more like 3p per mile'; and those figures do include charging losses.

OK, we both understand where the other is coming from so I am happy to park our discussion here. 

I'm reasonably well informed about electricity prices and had moved from traditional E7 because the higher peak rate made it more expensive for my use pattern.  However, based on the limited info on the Octopus rates gleaned from these boards, I genuinely didn't realise they also had more expensive peak rates. So this discussion has been quite useful for me.  As a heavy peak user (ASHP) it has pushed an EV further away from being financially viable for me.