Tesla Powerwall, Timeshifting & E7/EV Tariffs

AllyDM

Dear all,

First post here, but I suspect there is some good wisdom to be had....

I live in a fairly energy intensive house. Old Victorian detached, three teenage children, several freezers, tumble drier, electric cooking appliances and oil fired heating. We have done all the obvious things such as LED lighting throughout, great loft insulation, etc...

My electricity use over the last 12 months was 9,800 KWh - so on average about 27KWh per day. (This is reducing this year due to things like putting a heat pump in for the hot-tub, using an air fryer vs the main oven etc...) I am currently with EDF on an E7 tariff and paying 36.74p day rate and 16.52p for the E7 rate. Sadly, most of my energy usage is on the day rate. We do always set things like dishwashers, tumble dryer and washing on a timer to run on E7 as much as possible.

So, I want to get a Tesla Powerwall or two fitted and charge them using the E7 tariff, then use that cheaper rate electricity to run the house during the day. That seems pretty straight forward so far - and prices of Powerwalls have come down a lot recently, plus they are now zero VAT rated if installed without solar. (Solar PV is another story entirely - but for the purposes of this thread, let's just consider it off the table for now). I have been quoted £7,600 for a Powerwall 2, with Gateway supplied and installed. 

I am pretty rural here, and we get fairly frequent power cuts, so the ability to island the house via the Gateway and still have power in a power cut is pretty appealing.

Doing the maths, if I can charge the Powerwall overnight at 16.52p for 13.5KWh, and then use those 13.5KWh during the day, I save (36.74 - 16.52 20.22p on each KWh, or £2.73 per day. If I do this every day of the year, I save £996 a year and the Powerwall basically pays for itself in under 8 years.

Now, I have no time for EDF and want to switch provider. I can get slightly cheaper E7 rates, but they all seem to be within a penny or so of each other. No big deal.

However, a friend of mine has an EV and is on a tariff with Octopus that gives a discounted rate of 7.5p per kWh for five hours or so. I do not have an EV, and currently there is no EV made that suits my purposes. He is also getting a Powerwall fitted and will be able charge at the 7.5p rate. This make a big difference. (36.74-7.5 = 29.24 saving per KWh) x 13.5 x 365 = £1,440 saving per year = a 5 year payback.

Anyway, sorry for the rambling, but my basic questions are:

1) Who has the best E7 tariff these days?

2) Can I get onto an EV type tariff without an EV? i.e. can I claim that I have one, get the tariff and then just use it. The usage profile would be almost identical to charging an EV overnight anyway. I think I read that the Octopus EV tariff requires one "smart charge" to activate in the first instance....but if my friend were to bring his EV round and we plugged it in via a 13A plug, would that potentially work?

3) Are there any other options for non E7 type reduced rate tariffs that might make sense? I am sure I am not the only one looking at this type of option.

Anyway, thanks in advance for any constructive input!

dunstonh

1) Who has the best E7 tariff these days?

EDF for most of last year.  Not so good in Q4 but recent threads suggest it is EDF again.   I have seen recent posts showing 10p-11p as the off peak rate.  Not as good as their 8p off peak that I fixed on last Summer but better than their Q4 rates and hopefully will continue to fall towards summer.

2) Can I get onto an EV type tariff without an EV?

No.

The usage profile would be almost identical to charging an EV overnight anyway. I think I read that the Octopus EV tariff requires one "smart charge" to activate in the first instance....but if my friend were to bring his EV round and we plugged it in via a 13A plug, would that potentially work?

That is what economy 7 is for.

 I am sure I am not the only one looking at this type of option.

I am considering similar.  We already draw about 50kW overnight but then use 8-10kW during the day.  Like you, rural and suffer around 12 power cuts a year.   So, multiple advantages.  We are just toying whether to add panels or not.  The case for panels is not quite as clear cut 

Keep_pedalling

You can have the Octopus Go tariffs with a plug in hybrid, so that might be worth considering. 

AllyDM

Keep_pedalling said:

You can have the Octopus Go tariffs with a plug in hybrid, so that might be worth considering. 

Thanks, that's interesting. 9p per KWh. But only for 4 hours. But the Powerwall apparently charges at 5KWh - so that should be more than enough time to charge it from 0 to 100%.

I'd need how to figure out to "prove" I had a plug in hybrid though.

And the day time tariff is 31.2p, so there's a saving to be had there as well.

Netexporter

The Givenergy All-in-One offers a better spec for less money than the Powerwall. 6kW charge/discharge, 13.5kWh useable storage, instantaneous islanding.

AllyDM

dunstonh said:

1) Who has the best E7 tariff these days?

EDF for most of last year.  Not so good in Q4 but recent threads suggest it is EDF again.   I have seen recent posts showing 10p-11p as the off peak rate.  Not as good as their 8p off peak that I fixed on last Summer but better than their Q4 rates and hopefully will continue to fall towards summer.

2) Can I get onto an EV type tariff without an EV?

No.

The usage profile would be almost identical to charging an EV overnight anyway. I think I read that the Octopus EV tariff requires one "smart charge" to activate in the first instance....but if my friend were to bring his EV round and we plugged it in via a 13A plug, would that potentially work?

That is what economy 7 is for.

 I am sure I am not the only one looking at this type of option.

I am considering similar.  We already draw about 50kW overnight but then use 8-10kW during the day.  Like you, rural and suffer around 12 power cuts a year.   So, multiple advantages.  We are just toying whether to add panels or not.  The case for panels is not quite as clear cut 

Thanks. Yeah, I had really good E7 rates from EDF last year, but then they adjusted it way up from about 7p to the current 16p. But I hate them as a company - had major run-ins with them last year over the day rate they were charging and sticking that up sky high. I ended up getting the Ombudsman involved but to no avail.

As for the solar, I do already have a small 1KW array that is about 10+ years old, so I may replace it. I figure I should be able to get about 4.8KW onto the same roof now, so I need to do the maths on that but am waiting for quotes from the guys who are going to do the Powerwall install.

Keep_pedalling

AllyDM said:

Keep_pedalling said:

You can have the Octopus Go tariffs with a plug in hybrid, so that might be worth considering. 

Thanks, that's interesting. 9p per KWh. But only for 4 hours. But the Powerwall apparently charges at 5KWh - so that should be more than enough time to charge it from 0 to 100%.

I'd need how to figure out to "prove" I had a plug in hybrid though.

And the day time tariff is 31.2p, so there's a saving to be had there as well.

Intelligent Octopus Go Is cheaper 7.5p for 6 hours 23:30 - 05:30. That tariff requires a compatible car or charge point and to get started you need to do a test charge. Works well with my Zappi charge point. You also need smart meters of cause. 

Good to know the cost of the PW has come down, we will be moving to a bungalow with 12 solar panels fitted but no charge point or battery, which will be top of my to do list once we move. 

dunstonh

Thanks. Yeah, I had really good E7 rates from EDF last year, but then they adjusted it way up from about 7p to the current 16p. But I hate them as a company - had major run-ins with them last year over the day rate they were charging and sticking that up sky high. I ended up getting the Ombudsman involved but to no avail.

I have mixed views on them.  They are either excellent or rubbish but nothing in between.

We got our fuse updated to 100amp in readiness for the batteries/solar/charger etc.    To do that, we needed our meter tails updating and a cut off and smart meter installed.    EDF did both next day.  That was fantastic as we had been warned by the electricians that it would 3-6 months.    However, EDF transposed the readings and it took four months and multiple complaints to get resolved.  That was rubbish.

Since they moved to Kraken, the billing has been virtually the same as other kraken users and very easy.  So, I am tolerant of them because looking forward, there is very little that can go wrong with them now.

Scot_39

AllyDM said:

Dear all,

First post here, but I suspect there is some good wisdom to be had....

I live in a fairly energy intensive house. Old Victorian detached, three teenage children, several freezers, tumble drier, electric cooking appliances and oil fired heating. We have done all the obvious things such as LED lighting throughout, great loft insulation, etc...

My electricity use over the last 12 months was 9,800 KWh - so on average about 27KWh per day. (This is reducing this year due to things like putting a heat pump in for the hot-tub, using an air fryer vs the main oven etc...) I am currently with EDF on an E7 tariff and paying 36.74p day rate and 16.52p for the E7 rate. Sadly, most of my energy usage is on the day rate. We do always set things like dishwashers, tumble dryer and washing on a timer to run on E7 as much as possible.

So, I want to get a Tesla Powerwall or two fitted and charge them using the E7 tariff, then use that cheaper rate electricity to run the house during the day. That seems pretty straight forward so far - and prices of Powerwalls have come down a lot recently, plus they are now zero VAT rated if installed without solar. (Solar PV is another story entirely - but for the purposes of this thread, let's just consider it off the table for now). I have been quoted £7,600 for a Powerwall 2, with Gateway supplied and installed. 

I am pretty rural here, and we get fairly frequent power cuts, so the ability to island the house via the Gateway and still have power in a power cut is pretty appealing.

Doing the maths, if I can charge the Powerwall overnight at 16.52p for 13.5KWh, and then use those 13.5KWh during the day, I save (36.74 - 16.52 20.22p on each KWh, or £2.73 per day. If I do this every day of the year, I save £996 a year and the Powerwall basically pays for itself in under 8 years.

Now, I have no time for EDF and want to switch provider. I can get slightly cheaper E7 rates, but they all seem to be within a penny or so of each other. No big deal.

However, a friend of mine has an EV and is on a tariff with Octopus that gives a discounted rate of 7.5p per kWh for five hours or so. I do not have an EV, and currently there is no EV made that suits my purposes. He is also getting a Powerwall fitted and will be able charge at the 7.5p rate. This make a big difference. (36.74-7.5 = 29.24 saving per KWh) x 13.5 x 365 = £1,440 saving per year = a 5 year payback.

Anyway, sorry for the rambling, but my basic questions are:

1) Who has the best E7 tariff these days?

2) Can I get onto an EV type tariff without an EV? i.e. can I claim that I have one, get the tariff and then just use it. The usage profile would be almost identical to charging an EV overnight anyway. I think I read that the Octopus EV tariff requires one "smart charge" to activate in the first instance....but if my friend were to bring his EV round and we plugged it in via a 13A plug, would that potentially work?

3) Are there any other options for non E7 type reduced rate tariffs that might make sense? I am sure I am not the only one looking at this type of option.

Anyway, thanks in advance for any constructive input!

One heavy use E7 off peak poster found deals as much as 4-5p cheaper elsewhere off peak when EDF hiked his Eastern sub 10p rate.

As rates are predicted to fall dramatically by summer (near 8p) you may want to revisit payback calcs.

Have you done the maths just based on savings on single rate and not spending the £15k on powerwalls.

After all you imply current use doesn't warrant E7 without heavy investment.

QrizB

AllyDM said:

I am currently with EDF on an E7 tariff and paying 36.74p day rate and 16.52p for the E7 rate. Sadly, most of my energy usage is on the day rate.

If you don't use electricity for heating, E7 is unlikely to make much sense. You'd probably save money on a standard tariff.

How many of those 9800kWh are night-rate?

And, if you'll excuse me saying, 9800kWh a year is a crazy amount of electricity for a property that doesn't use it for heating. It's getting on for four times the average household. Do you know where it all goes?

AllyDM said:

Doing the maths, if I can charge the Powerwall overnight at 16.52p for 13.5KWh, and then use those 13.5KWh during the day, I save (36.74 - 16.52 20.22p on each KWh, or £2.73 per day. If I do this every day of the year, I save £996 a year and the Powerwall basically pays for itself in under 8 years.

I don't think you are doing the right maths there.

Single rate electricity is currently around 27p/kWh (shortly expected to fall). That's the price you'd be paying without the Powerwall.

Plus, you lose perhaps 10% of the electricity you cycle through a Powerwall.

So, your effective cost of E7 through a Powerwall is 16.52 x 1.1 = 18.17p/kWh. That's a saving of 8.83p vs. standard rate electricity, £1.19 per day, £435 a year. You're looking at a 17-year payback period, which could be longer than the life of the Powerwall.

I think you would be better off looking at how much you would save on a standard tariff, and seeing if you can reduce your electricity use to something closer to the norm.

AllyDM

Scot_39 said:

One heavy use E7 off peak poster found deals as much as 4-5p cheaper elsewhere off peak when EDF hiked his Eastern sub 10p rate.

As rates are predicted to fall dramatically by summer (near 8p) you may want to revisit payback calcs.

Have you done the maths just based on savings on single rate and not spending the £15k on powerwalls.

After all you imply current use doesn't warrant E7 without heavy investment.

Thank you. Good points. 

I actually have not done the maths on single rate, having just assumed that a decent E7 rate was always going to be much cheaper, and if I can take advantage of that for most or all of my needs then it would almost certainly be better.

I'll run the numbers on that.

But something else to consider as well. The reason I said that solar was off the table for this discussion was that I already have a 10+ year old small PV array of 1.2kW and will probably be replacing that this spring with something more like 4.8kW, so there are other factors at play. But I did want to try to evaluate Powerwalls without any added benefit of PV.

The main thing that annoys me with E7 tariffs is the assumption that people use 42% of their energy on the E7 tariff. Which might be true if you use electric storage heaters to heat you home, but can't really be true for most users. So EDF give a crazy high rate for Day (I think it was 45p at one point) and then a very low rate for E7 (something like 6p at one point), knowing they will win. So my thinking of timeshifting to take advantage of that. However, at the current 15p or whatever, it's not as good a saving as last year. Still, if it goes down to 8p, then the saving is huge.

All that said, I may not need 2 Powerwalls. 2 would certainly let me take 100% of my needs to E7 pricing, but 1 would go a long way anyway - especially with some PV. Again though, it comes down to long term ROIC and payback.