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Comparing Electricity price plans -- there's not as much in it as you think

rotor2k

Member
Sep 16, 2019
524
293
London
Power Consumption.xlsx

I've put together a comparison of three different electricity price plans: Octopus Agile (I averaged the entire year worth of sample data they give to get each half-hourly price), Octopus Go, and Bulb E7. I live in London, so all the prices I've used are for London. The inputs to the spreadsheet are:

- Your average load (this would be how many kWh you consumed in a month excluding car charging and any "heavy" overnight stuff you do, divided by 30 divided by 24). I chose 0.4kWh because that is what my GlowStick tells me I am consuming most of the time (I have some servers running 24x7 which bumps that up a bit from most normal people would have). This is your lights, washing machine, dishwasher, etc.
- Your car charging. I have set this to 32A x 240V = 7.68kWh
- "Heavy" Load: this is overnight stuff you would do, like night store heaters, heating up under-floor gigantic concrete pads, etc. I've set this to 3kWh (I have no idea what a good figure is, I just made this up).
- The actual electricity rates themselves, in half-hour increments.

You then get to specify (using Xs) which half hour slots of the 24h of the day are consuming the "car charging" and "heavy load" portions. I've chosen 3h for car charging, and 5h for heavy load stuff. In each of the 3 price plans, I've put these loads in the cheap zone (well in Agile I tried to pick what roughly looked like the cheapest block of rates).

Two main conclusions:

- Agile doesn't seem cheap, at all. Maybe averaging across the whole year is the wrong approach, but I don't know how else to analyse it apart from some complex modelling over an entire year.
- There is not a huge difference between Go and E7. In fact I would say there may not be much point in getting too excited about the whole thing, as long as you have a plan that offers you a cheap rate for at least a few hours of the day. Charging the car at daytime rates is triple the cost, so it makes clear sense to charge during the off-peak. But which particular off-peak plan you choose seems to be less interesting.

Let me know what you think, and if you find any mistakes or have any ideas for improvement.
 

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
Fits, more or less, with my conclusions. I have been keeping a running spreadsheet of costs, and scraping Agile data from this chap's website: Home - Energy Stats UK

At the moment, Agile is the most expensive tariff, by a fair way (around 20%). E7is a few percent cheaper than Go, but it seems that, since I've had the M3, E7 has been even better value (probably down to me not charging every night, though, so charge periods tend to be over the 4 hour Go window). I could probably change behaviour to reduce the Go price back to what it would have been when I had the i3, easily enough, but it would still cost a few percent more than E7.
 

gangzoom

Active Member
May 22, 2014
1,375
1,231
Uk
Two main conclusions:

- Agile doesn't seem cheap, at all. Maybe averaging across the whole year is the wrong approach, but I don't know how else to analyse it apart from some complex modelling over an entire year.
- There is not a huge difference between Go and E7. In fact I would say there may not be much point in getting too excited about the whole thing, as long as you have a plan that offers you a cheap rate for at least a few hours of the day. Charging the car at daytime rates is triple the cost, so it makes clear sense to charge during the off-peak. But which particular off-peak plan you choose seems to be less interesting.

Pretty much my conclusion as well, though when Excel crashed on me when I first did the Agile calculations I haven't bothered again.

Agile is 100% not cheaper than E7, not even close.

Go gets close but it depends on your E7 usage, another forum member posted their Go bill recently, for essentially the same amount of total electricity usage their bill was £5/month more expensive than my E7 bill.

Octopus have pulled of a massive PR win with their clever product placement/push, for nearly all consumers Agile is going to be costing them more, and Go is on par with E7 at best.
 

Akikiki

A'-Lo-HA ! y'all
Nov 26, 2012
6,520
4,878
Kaneohe, HI
Sounds like a plot for a Netflix movie where a journalist digs deep into records and shell companies to discover some foreign company owns all three of those UK electric companies. One way or another they get your money.
 

Jason71

Active Member
May 8, 2019
3,189
3,254
Shropshire
If you can get all your charging in in 4 hours then I imagine Go is going to be a winner if not its probably E7. and if you are on electric heating its probably E7 either way.
For a lot of people it's more about the meter. Many people live places where smart meters simply don't work and trying to get an E7 meter fitted these days if you don't already have one can also be very challenging. These factors can outweigh the potential savings
 

Tony Hoyle

Active Member
May 7, 2019
1,183
741
Stockport, UK
It's quite individual.. Tracking my usage gave Agile slightly cheaper than Go which was slightly cheaper than Bulb, with E7 the most expensive.. but not huge amounts in it (£20 either way over a year), and wouldn't be unhappy to pay any of them.

Compared to the higher standard charges that lots of people on we're all getting a decent deal.
 

ivangr

Member
Jul 22, 2019
198
125
dunfermline
If you can get all your charging in in 4 hours then I imagine Go is going to be a winner if not its probably E7. and if you are on electric heating its probably E7 either way.
For a lot of people it's more about the meter. Many people live places where smart meters simply don't work and trying to get an E7 meter fitted these days if you don't already have one can also be very challenging. These factors can outweigh the potential savings

I’m on GO and we really try to make the most of it. We run the dishwasher, washing machine, tumble dryer and the car on a schedule to start at 00:30. My car finishes charging in the 4 hours just fine.

I did the XLS maths on Agile too. It seemed there weren’t that many low cost events and on average it wasn’t that cheap. You would always get beaten at tea time when the rate is very high. I see people tweeting about saving money on Agile though.
 

hmy7k

Member
Nov 7, 2019
95
62
Shropshire
I am on Agile, but I have 7kw of solar and use Octopus outgoing for my surplus electricity.

I would have chosen the Go tariff but they won't allow you to have the Go tariff with Outgoing.
We don't have a significant usage during the peak hours and in summer probably none so the penalty isn't that great.

Hopefully when the new rules come in forcing all suppliers to buy your surplus generation there will be more choice of tariffs.
I am happy with Agile as it fits my needs at the moment but I think there will be better tariffs around in the near future.
 

rotor2k

Member
Sep 16, 2019
524
293
London
I’m on GO and we really try to make the most of it. We run the dishwasher, washing machine, tumble dryer and the car on a schedule to start at 00:30. My car finishes charging in the 4 hours just fine.

I did the XLS maths on Agile too. It seemed there weren’t that many low cost events and on average it wasn’t that cheap. You would always get beaten at tea time when the rate is very high. I see people tweeting about saving money on Agile though.
Based on how the average rates worked out, I do wonder if their savings are momentary, but not sustained over the year.
 

kuruma

Member
Aug 29, 2019
315
144
Northeast
I'm considering moving from an E7 tariff to Go because we only use off peak energy anyway with the powerwall now installed. The powerwall runs the whole house for the rest of the day.

The Go tarrif would be half what we're currently paying with standing charge identical. Is this the no-brainer it looks like to me?
 

im85288

Member
Aug 31, 2019
86
72
Newcastle
I'm considering moving from an E7 tariff to Go because we only use off peak energy anyway with the powerwall now installed. The powerwall runs the whole house for the rest of the day.

The Go tarrif would be half what we're currently paying with standing charge identical. Is this the no-brainer it looks like to me?

Having only recently entered this game, car received start of November and then Solar PV (7.8 kw) plus powerwall installed mid November I can only go off my current experience. Solar is producing about 3-4 kw per day, powerwall charges every night during the GO off peak and most of the time sees me through the whole peak period. So in my simple maths getting the electricity at 5p and not buying any at the peak rate seems to be a winner. The standing daily charge is slightly more than other providers and the peak is more than what I had previously with Shell Energy.

So after all that I would say if you can limit to charging the car/powerwall in the 4 hours off peak it has to be a winner!
 

Glan gluaisne

Supporting Member
Supporting Member
Sep 11, 2019
2,782
2,912
UK
I think that the key thing is to try and gather as much information as you can about your particular pattern of usage, perhaps play around with changing the time of use of high loads for a while, to see what impact that has, then have a look at the data to see which tariff looks to be the best fit. The fly in the ointment is Agile, as it's not easy to predict what the Agile rates will be. The link I gave earlier to the chap's website that scrapes and aggregates Agile data is useful though, if you can compare usage to that fine a resolution.

Also, I've found that it's generally not a great idea to make a decision to switch during the winter. May just be to do with our pattern of use, but the standing charge can be a fair proportion of our total bill in summer, so a low standing charge tariff can look better, even if the unit price is a bit higher. Whilst we were building this house I had a zero standing charge tariff, with a pretty high unit price, as, on balance, that worked out a fair bit cheaper, given that the house was using no electricity at all for more than 12 hours every day.
 
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kuruma

Member
Aug 29, 2019
315
144
Northeast
all helpful thanks. Seeing as the standing charge is equivalent to my current supplier but the off-peak rate half the price, it makes sense to switch whenever rather than wait until summer.
 

MaDProFF

Member
Jul 26, 2019
415
135
East Sussex
if you are using storage heaters and wreckers 24/7 maybe look at EDF their electric car tariff, 98 hours off-peak (it includes all weekend) at around 8p KWH day rate is about 16p I think
 

tess19

Member
Jun 28, 2019
432
243
birmingham
Is it possible to get a powerwall and get it charged up between 12:30 and 4am? Then use the power for the rest of the day? If so, i'd be tempted to go for a powerwall
 

kuruma

Member
Aug 29, 2019
315
144
Northeast
I've been waiting for the "pay for itself" vultures to gather... None of us are going to pay for our cars either but it didn't stop us buying them. There are other reasons people buy this stuff.

Yes, you can tell the powerwall to charge up at any time of day you schedule and then run your house off it for the rest of the 24 cycle. On that setting, any power demand will come out of the powerwall while it has charge, even if you plug in your car.

People's Energy's E7 tariff is the same as the EDF one you mentioned above. But, with VAT, that's still twice Octopus Go... and if you're never going to use the peak rate, it doesn't matter how high it is.
 
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gangzoom

Active Member
May 22, 2014
1,375
1,231
Uk
How much does a PowerWall cost, though? I keep seeing videos on it, but haven't seen an economic analysis.

£8-10k installed, if your paying it your self than very little chance of it financially making sense.

12.5kWh real energy delivered per charge. Be generous and say by 'shifting' to off peak you save 10p per kWh AND you use the full 12.5kWh, it will take you 17 years to become cost neutral.

Don't get me wrong, its a great product, in many ways more useful than the cars - ours is constantly either charging or discharging. But am not sure I would have paid for it my self - ours was 'free' from Tesla as part of the old referral prize system.
 
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