Octopus Tesla and Powerwall

[phil4]

I was watching a video from a US youtuber about why they shouldn't have bought a powerwall. It was quite interesting... link here:

I then thought "I know octopus do a tesla tarrif, I wonder what that entails?". And found that it too is a synchronous priced tarrif. It's this: Octopus Energy Ie same price per Kwh buy and sell.

So this then brings me to wonder, as the US chap mentions... the logic of having a powerwall in this instance. As he says, when you have the same buy/sell price - with the exception of the odd powercut, the grid is your battery, when you generate solar instead of putting it in the power wall, put it back to the grid... then when you need it, save using your battery, buy it back from the grid at the same price.

So what's the logic of using the Octopus tesla plan? It sounds like they take control of your powerwall usage, which makes sense for them. And for you it sounds like in return you get a low rate (10-12p/kwh), and because it's the same buy/sell price you get an infinite battery. In an ideal world you wouldn't buy a powerwall, but it's the only way to get that tarrif.

Any ideas if I've missed the point?

 

[Rav-Y]

In my opinion: the power wall is primarily bought for backup power. Everything else is to help pay for it. It is not meant as a way to make or save money. That is a bonus.

Environment: Solar power helps the grid when energy is most needed. This power is usually provided by fossil fuel so home solar power reduces how much of it is used.

Grid Stability: Power wall battery power is most useful when there are sudden peaks and waiting for the fossil fuel power to catch up.

Economic: By joining the grid with solar the utility gets power when it is most expensive on the wholesale market which is much higher than the home owner’s rate for both buy and sell.
By joining the grid with a power wall it gets grid stability. Peaker power plant energy is the most expensive because assets are idle most of the time. Peaker power from batteries is cheaper.

When there is enough home generated capacity to become a significant percentage of the grid homeowners will be in a position to demand better rates. Virtual power plants like octopus become more of a player. The only way for the home owners to get better rates is competion and choice.

 

[Mr Miserable]

Octopus provide a calculator (the link is provided in the 1st post) and you should find that the savings can be appreciable.

 

[Mark_T]

Octopus provide a calculator (the link is provided in the 1st post) and you should find that the savings can be appreciable.

It was a decent tariff, but there were recent changes that make it much less appealing now.

There are better options with Octopus like their 'Go Faster' tariff for example that can deliver lower per kWh costs and leave you in control.

With the tariff as it is, you bear the cost of the round-trip losses and they get to cycle your Powerwall at least once a day but sometimes more...

Certainly do your own maths as the calculator assumptions were way off base for my use.

 

[ACarneiro]

Had a brief look. I don't think the current Powerwall is perfect for someone running a mansion with a peak power draw over 50kW and a daily electrical usage over 200kWh! You'll be very hard pressed to find a European home with that level of power usage, IMHO.

 

[Gatsojon]

It’s 8p in and out with zero standing charge. Works well for me in the summer months. They have not taken control of the Powerwall as yet.
A friend with an LG battery system does better. He is on Go for incoming and agile export for outgoing. So charges the battery at night at 5p per kWh then sells around 5 to 7 pm at around 20p. Excess solar is sold at whatever the rate is when produced. If the forecast is for a sunny day, then obviously it doesn’t charge at night.

 

[Mark_T]

It’s 8p in and out with zero standing charge.

Not any more it isn't, the 8p rate has gone for new customers and there is a standing charge...

Currently 11.24p/kWh and 22p SC for Eastern region.

 

[Mark_T]

A friend with an LG battery system does better. He is on Go for incoming and agile export for outgoing.

If he is, it is an accident on Octopus's part, as Agile Export cannot be combined with 'Go' under their rules.

The only export option for him should be the 3p SEG tariff...

 

[browellm]

He is on Go for incoming and agile export for outgoing.

Be interesting to know how he's managed that. Agile export is explicitly for customers on Agile import.

edit: beaten to it by @Mark_T

 

[Gatsojon]

Not any more it isn't, the 8p rate has gone for new customers and there is a standing charge...

Currently 11.24p/kWh and 22p SC for Eastern region.

Really? Well I won’t be taking that option thank you. I’ve another 9 months at 8p so will make the most of that.

 

[SpareHeadOne]

In my opinion: the power wall is primarily bought for backup power. Everything else is to help pay for it. It is not meant as a way to make or save money. That is a bonus.

Yep, that was one of the primary reasons we got one fitted. In our case we're also on an older feed in tariff that pays us for 50% of the solar we generate, so the powerwall price is slightly offset by the difference between that and what we can store too.

Last year we generated 2.5mWh, used 56% directly, stored a further 39% in the Powerwall and sent 5% to the grid meaning we now may use of almost everything we generate. We also had 25 minutes of grid outages that went completely unnoticed except for the app alerts that they had happened.

Even without the FIT payments it would still make a saving of £150-200/year over the solar on its own, so nowhere near enough to make economic sense unless prices carry on going up.

Where things are more interesting is using it with a tariff like Economy 7, that's also allowed us to run on night rates for around 85-90% of our usage as well, even in the middle of winter. I guess you'd have to do your own calculations, but I estimate that saves us around £400/year as well.

So, with solar and Economy 7 it might pay for itself in around nine years - about when the warranty expires - but that is based on current prices, so the payback time will probably shorten. It's a gamble on that front, but our regular power failures have killed some expensive kit in their time and that has run into four figures on several occasions.

 

[Mark_T]

Really? Well I won’t be taking that option thank you. I’ve another 9 months at 8p so will make the most of that.

You might get lucky, the tariff is still there although it has gone up a bit (8.72p/kWh 22p SC Eastern), so you might get grandfathered into a renewal...

 

[ElectricJoules]

I'm on Octopus go at present, for night time M3 charging, with solar panels recently installed and a powerwall arriving soon. I'm thinking I'll be able to set the system to charge the powerwall during the 12:30 to 4:30am cheap slot, and then use the powerwall to supply the home during low solar periods. That way I'll only ever use free solar power or 5p per kWh. Does that sound feasible?

 

[Dilly]

I'm on Octopus go at present, for night time M3 charging, with solar panels recently installed and a powerwall arriving soon. I'm thinking I'll be able to set the system to charge the powerwall during the 12:30 to 4:30am cheap slot, and then use the powerwall to supply the home during low solar periods. That way I'll only ever use free solar power or 5p per kWh. Does that sound feasible?

Yes it’s feasible. I do that. The power wall settings in winter don’t always behave as planned, particularly after a couple of unseasonably sunny days!

 

[johnmwingnut]

I’ve just renewed our Tesla Energy plan, as our home runs off an air source heat pump for heating, so we get through 30kw a day easily in winter, and I think when I looked at the Go tariff the day rate would end up costing us more, as 14kw stores from night time charging would only cover max, half the day.

 

[PITA]

At our house we have two Tesla Powerwall 2 batteries, a Tesla Gateway 2, a Solar Array and Wall Charger. It's a really nice setup... with a new Tesla Model 3 Performance being collected next week.

I chose to run with Octopus Go, and we download Grid power during the night in a 4 hour low tariff window (if needed) at 5p per 1kWh.

So 20 kWh costs us £1 ... and we use that power during the day if the Sun isn't reaching us.

I looked at the Tesla Virtual Grid tariff as we qualify (Powerwall & Solar) but decided against it.

Reason being ALL our power gets used. The house has a Toshiba Haori climate control heat pump, backup battery storage and the M3P EV outside.

Tesla Virtual Grid tariff will not allow you to use your Solar for Car Charging... everything has to go to them... but... I want to use our Sun Power for my car... it makes me feel good.

So if you're using more than you're exporting it starts to get expensive... and they control your batteries whereas I'd rather do that myself thanks.

 

[Fred2]

Hmm that bit about not being allowed to use solar for car charging doesn't sound right - I definitely do that when the sun is shining (not that it's done much of that recently).

 

[johnmwingnut]

On my Tesla plan, once my Powerwall is full, I can charge off of solar, otherwise it just gets exported!

I have a 7kw solar array, 2 x electric cars, 12kw heatpump, solar thermal hot water, and 1x power wall.

On average across the whole year, we are using 28Kwh per day. Low day is 8.2Kwh and a high day is 77.9kwh. Looking at the Winter months, the average is 56.2Kwh per day, with a high day of 115.2kwh. The summer is naturally much less, during which we are pretty much exporting 40% to the grid everyday, as it doesn't all get used. In the winter, solar generates approx 7-8kwh per day. Powerwall is say 13kwh usable with losses, so we have a short fall, which gets very expensive outside of the 4 hour Go window.

Lets say, during winter, I could charge my car at 7kwh and Powerwall at 5kwh during the 4 hours window, Im only going to get 42kw of benefit. I can ignore export benefit as I dont export anything in the winter due to lack of solar.

Average Day:
42kw x 0.05 = £2.10
14kw x 0.16 = £2.24
+0.25p SC = £4.59
vs
56kw x 0.083+0.22p = £4.87

Heavy use day:
42kw x 0.05 = £2.10
73kw x 0.16 = £11.68
+0.25p SC = £14.03
vs
115kw x 0.083 + 0.22p = £9.77


Then, for me during the summer, I export around 40% of solar, so get huge cost recoup via that, along with the fact I import around 40% less as well,

Go Tariff would work out much more expensive for me personally, plus I am free to use energy when I would like too, rather than during defined periods.

 

[PITA]

Hmm that bit about not being allowed to use solar for car charging doesn't sound right - I definitely do that when the sun is shining (not that it's done much of that recently).

Maybe I misread/misunderstood this on the Octopus FAQ Page

"Electric vehicle chargers that use solar excess to trigger vehicle charging could also create a conflict with Tesla Energy Plan, so to avoid such conflicts you must turn off any diversion of excess solar to smart vehicle chargers; joining with such devices enabled risks the plan being unable to operate as intended."

 

[Fred2]

Ah, so what they are saying is that if you have a zappi or something that automatically charges when there is excess solar then that will clash with what they are also trying to do with excess solar. They also caution against automatic immersion heaters, for the same reason. I think in particular those devices could sense you exporting and there go “hey it’s a great time to charge/heat water” but actually the export is coming from the battery, not your panels.

i don’t have a setup like that - I just put the car on to charge if it’s a sunny day. It may end up drawing some from the grid if there i put the kettle on, sun goes behind a cloud etc, but that is cost neutral since you pay the same for exports/imports