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Best Energy Providers [UK]

Mr Miserable

Well-Known Member
Supporting Member
Jul 8, 2019
5,714
11,071
UK
Step C: Calculate on-peak / off-peak usage
  1. This is where things get interesting. First, you need to understand the 'split' (on- vs off-) for the different tariffs. For EDF GoElectric this is 2100 - 0700 (10hrs) plus all day Sat & Sun. For Octopus Go this is 0030 - 0430 (4hrs).
  2. Next, I needed to calculate how the 6,000 KwH would be split between on- and off-peak. First, I needed to understand EV charge time, which is based on a 7KwH Tesla Wall Charger and a 50KwH requirement would be c. 7hrs.
  3. I am now ready to calculate KwH split: I did this in two phases; first the previous 12 months (2,000 KwH) and secondly the new EV charging (c 4,000 Kwh). The key factor here is the duration of off-peak rates.
  4. As the EDF off-peak rate lasts 10hrs plus weekends, and average charge takes under 10hrs, I was able to allocate 100% of the 4,000 EV-related KwH charging to the off-peak rate. I also shifted some of the previous 12 months (2,000 KwH) into off-peak based on an estimated on- vs off-peak usage (excluding EV charging). This resulted in 1,200 KwH on-peak and 4,800 KwH off-peak for EDF.
  5. For Octopus Go, only 4hrs (57%) of the 7hrs of charge would qualify for off-peak charging. Thus, I calculated 57% of the 4,800 KwH off-peak usage from EDF (equal to 2,736 KwH) as Octopus Go's off-peak usage, and therefore a further 3,264 KwH on-peak use.

I get the impression that you are still thinking of charging as refuelling but there is a different mindset for charging.
The idea that you would charge 50kWh at a time is a bit odd. If you went for the Octopus GO tariff, you would want to maximise use of those 4 hours and so would charge accordingly. At 400 miles per week, the 4 hours per night is ample. It may surprise you but there is a subtle change of mindset when you become an EV owner and a little often is the way ahead.
 

Adopado

Active Member
Aug 19, 2019
4,882
3,700
Scotland
Therefore you will be charging smaller amount each night and starting each day at your 80% or 90% setting.

For anyone that uses their car regularly this is an important point. There's no advantage to setting off from home with a less than optimal state of charge, just so that you can only charge a coupe of times a week. This is a different mind set to when you drive a petrol or diesel car where you tend to fill up then run it as far as you can before filling up again. If you have home charging then plugging in routinely when home is easy and convenient ... you don't have to go to a petrol station and stand around and wait in the queue whilst other people pay for their sweets, soup, sandwiches ... so there's no pain in charging a small amount every day. It also means you can pre-heat the car with no battery range penalty. (But ... if your pattern of use genuinely is so low (e.g. during lockdown) then fair enough, charge once a week or whenever.)

On long trips you top up with what you need for the next leg of journey plus a safety margin. If using Supercharging this can make stops very short. New owners are distracted by the quotes of charging speed that you read. EV drivers are rarely (if ever) charging from zero and they are even less likely to be charging from zero to 100%.
 

Jeeves

Member
Feb 12, 2020
611
355
UK
Mmmm, I get all your logic, but I still don’t understand how your weekly mileage would be made up in terms of trips. That will dictate how much juice you will need and when to put it in. I think the answer to that question might call into question your assumption in Step B of your analytical process.

@VanillaAir_UK has given you some great efficiency stats that will help you make better assumptions, as have I and the others about real-world use.

As I wrote, all that translated into a 45–60kWh requirement per night for me, so I concluded that the 8p/kWh deal that I got from EDF was fantastic. In practice so far, Agile Octopus almost always beats that overnight by some margin and obliterates the 18.6p/kWh daytime that I got from EDF except between 16:00 and 19:00.

I recall reading somewhere that ‘a plugged in Tesla is a happy Tesla’. Many people like me do this and use various techniques to ensure the peak period is avoided for charging but get it to 80-90% by your usual departure time in the morning irrespective of whether I’m departing or not. The car is then ready to go should I need to use it. Personally, I’ve managed to optimise charging costs with the ev.energy app, but many here have reported difficulties with it.

As we’ve said, we’re talking of finessing small amounts of money in comparison with diesel, so you’ll be on a winner whatever tariff you go for. That said, I think your charging patterns might not work out quite as you currently expect. Probably a matter for consideration a few weeks after you have tempered your inevitable proclivity to floor it anywhere you feel safe to do so.;) It was some time before I managed to get down to that 350ish Wh/mile in winter, and the travel restrictions still imposed on me are making it even harder to experience what summer driving efficiency is supposed to be like.
 

JAR897

Member
Jun 11, 2020
197
171
Nottingham
Thanks all - So to confirm, the way of thinking for an EV *should* be to charge a small amount each night? ie. the 4hrs of Octopus Go's tariff?

And so to help me understand, imagine the scenario: Car at 90% (67WkH) charge when I leave, and when I return it is at 30% (22KwH). Correct me if wrong, but that's c. 180 mi used. In order to "refill" for tomorrow, I would need to "put in" 45 KwH which, at 7KwH charging would take 6hrs).

Are you suggesting therefore, that I would still only charge for the 4hrs, giving c. 7KwH x 4hrs (total 28 KwH), meaning the next morning I would drive with 50 KwH (66%) charged car? If I repeated this method each day, I'd be on 0% charge within 4-5 days, no? As I'm using 45KwH per day but only putting back in 28 KwH? A net negative of 17 KwH (c. 4 days to empty?).

Sorry - I am genuinely trying to understand before hitting the button on either EDF or Octopus Go.
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,954
6,543
Surrey, UK
I wouldn't get too hung up about not fitting a charge into a off peak window such as Go 4 hour.

Charge for your next journey needs and if that fits in the 5p/kWh off peak window thats great, but if it doesn't and takes 5 hours, that still averages out at under 7p/kWh and under 8p/kWh for up to 6 hours.
 
Thanks all - So to confirm, the way of thinking for an EV *should* be to charge a small amount each night? ie. the 4hrs of Octopus Go's tariff

In short yes.

In your example of going 67 to 22kWh, that's approx 160miles, you would be a very high mileage driver doing that every day(?). Pre-lockdown I did ~28k miles/year, which was mostly 100miles round trips to the office but also included various longer/shorter journeys, 4hrs top-up on Go each evening worked well. If I needed to charge for 5hrs one evening then no big deal as Vanilla air describes.

In practice I switched to Agile after a month or two and haven't looked back...
 
I will be having a similar pattern but I have a base commute mileage of 70-80 miles and then out and about visits which sometimes is none and up to 60 or 70 on a busy-ish day. On occasional days I know that 4hrs wont fully meet my consumptions and I concluded in my head that spending an extra hour or so a week at the higher rate isn't going to cripple my finances. There were other savings in my life that I could do to cover the extra in electricity.
 

Jeeves

Member
Feb 12, 2020
611
355
UK
Thanks all - So to confirm, the way of thinking for an EV *should* be to charge a small amount each night? ie. the 4hrs of Octopus Go's tariff?

And so to help me understand, imagine the scenario: Car at 90% (67WkH) charge when I leave, and when I return it is at 30% (22KwH). Correct me if wrong, but that's c. 180 mi used. In order to "refill" for tomorrow, I would need to "put in" 45 KwH which, at 7KwH charging would take 6hrs).

Are you suggesting therefore, that I would still only charge for the 4hrs, giving c. 7KwH x 4hrs (total 28 KwH), meaning the next morning I would drive with 50 KwH (66%) charged car? If I repeated this method each day, I'd be on 0% charge within 4-5 days, no? As I'm using 45KwH per day but only putting back in 28 KwH? A net negative of 17 KwH (c. 4 days to empty?).

Sorry - I am genuinely trying to understand before hitting the button on either EDF or Octopus Go.
Looks like you expect to use a lot on a travel day, so fill it back to 90%. You will use a bit more than 45kWh due to the charging inefficiency.
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,954
6,543
Surrey, UK
I will be having a similar pattern but I have a base commute mileage of 70-80 miles and then out and about visits which sometimes is none and up to 60 or 70 on a busy-ish day.

Sounds like worst case situation if your out and about visits are frequent. If you do lots of little trips, with a bit of a gap between them, efficiency will be far less than doing same aggregate mileage in a single journey. Some refer to a 'departure tax' that is energy incurred for each journey irrespective of distance and is especially bad when cold.
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,954
6,543
Surrey, UK
Octopus Go seems to be getting the nods for electric

Many people will vouch for Agile but I'm not so convinced at less extreme electricity usage figures than we are currently witnessing that its worth the hassle. Everyones usage will be different though and an EV will bring different usage patterns than you previously would have had.
 
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I’m currently with Bulb on their Vari-Fair tariff (don’t think there’s any others)

This is the thing, in comparison to some, our weekly mileage is fairly low key, about 120 a week.

paying about 70- 90 a month throughout the year on dual fuel with Bulb, so wondering if actually switching to say Octopus Go, would reap any great savings?
 

Mr Miserable

Well-Known Member
Supporting Member
Jul 8, 2019
5,714
11,071
UK
I’m currently with Bulb on their Vari-Fair tariff (don’t think there’s any others)

This is the thing, in comparison to some, our weekly mileage is fairly low key, about 120 a week.

paying about 70- 90 a month throughout the year on dual fuel with Bulb, so wondering if actually switching to say Octopus Go, would reap any great savings?

Have a play with this spreadsheet here to give you an idea of possible savings. It's electricity only.
 
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