Considering getting a Powerwall

[nightowl]

I have 4kW solar PV, with panels on both sides of the roof so peak power is generally a little over 2kW but I get a decent amount of exposure (time-wise). On a typical winter day I might get 1 or 2 kWh, in summer it's often in excess of 20 kWh. Got it installed just before the FIT prices dropped from ~12p/kWh.

Switched to Bulb back in spring last year and am on Economy 7 with a day rate that is twice the price of the night rate.

Recently had a Zappi and Eddi installed. Previously had a Solar iBoost which was happily dumping about 6 kWh daily into the immersion water heater (which is an old tank with very little insulation so that's something I'm looking to upgrade at some point so I'll probably be using less energy to heat it.)

Based on the Myenergi app readings, most of my usage is generally below 500w at all times except for the evening peak when food is cooking, using the washing machine, and of course when charging the car or powering the storage heaters (both of which happen on off-peak rate overnight.)

So far I've always been trying to time things like using the washing machine based on how sunny it is, which can be a bit of a gamble as sometimes it's bright for a bit and then it clouds over.

The Zappi should theoretically be able to boost the energy supplied to my car but there's an issue where the car doesn't wake up when charge is available from a Zappi in Eco+ mode, which is a little annoying.

Occasionally, I've read/heard about the Powerwall. We rarely have power cuts but it'd be nice to not have to worry about that. Being able to store the generated power and use it when it's clouded over or in the evening seems like it'd be making the most of my solar PV. And in winter, importing off-peak energy for use during peak times would save a bit of money.

But of course, it's expensive to buy in the first place. It would probably pay for itself eventually, but only after several years (i.e. probably after the warranty expires!) Part of me just wants it for the tech.

I've seen a handful of posts about it here but I'm wondering:
1. If you have one, what were your reasons for choosing it and how useful have you found it?
2. How long does it take to get one? (I'm hoping it doesn't take as long as a Model 3!)

 

[MrBadger]

You will save more waiting for price of batteries to come down than you save with the battery. By sounds of your setup, I don’t think you will ever see a financial break even. I would say your break even is a setup probably somewhere between £2-3k. Imho - I did the maths many years back when they were around 5k.

That said, I’ve still seriously considered buying on a few occasions.

 

[Mr Miserable]

On a pure financial model it doesn't make sense at all, especially now when 20% VAT is charged.
I like the tech and if I did buy one I would have to go with the gateway as well (extra £1.5k) as I would want to use the PW in the event of a power cut.
I've decided to delay any decision in the hope that the budget may bring an incentive. I have heard no suggestion that it will.

 

[ProfessorK]

I take the view point of "if you can afford it, definitely" - mostly because those of us who can shoulder the financial burden should aim for more renewable sources of energy - EV, solar, house batteries, biomas boilers etc. I would if I wasn't renting!

 

[im85288]

I had a 8kW Solar system installed around the end of November last year (3 weeks after getting my model 3 performance), along with a Zappi, Eddi and PowerWall. As mentioned above getting the powerwall at the same time as the solar PV allowed me to benefit from the 5% vat rate...but that’s all gone now.

Like others have mentioned if you sit down and crunch the figures it may not actually pay itself off but I chose it as I really wanted to have it! Plus as I missed the FIT I did not like the idea of sending back energy to the grid for free (the Smart Export Guarantee is now around but with Octopus Energy you cannot combine that tariff with the cheaper Go off peak tariff).

Without a shadow of doubt It’s the best bit of tech I have, during these last couple of months it charges up during the off peak period and usually gets me through most of the day. The last few days where solar generation has started improving I am getting to the 00:30 off peak time with roughly 20% battery still in place.

Yesterday was the day it really put a huge smile on my face. Around about 6pm alarms in the street and near areas started going off (the wind gusts were extremely severe here in Newcastle) and I received a notification via the Tesla app telling me my house was being backed up by the powerwall as grid power had been cut (in reality it was purely using the powerwall anyway but it was bragging!). Nothing stopped working, the internet, lights etc remained on. Eight minutes later the app informed me grid power had been restored. So we had experienced a power cut for about eight minutes and carried on as normal...I have to admit a sly grin was on my face as I looked out the window at the neighbours houses which were in total darkness.

So to try and answer your questions, I love mine and may get another once prices drop once I see what sort of power my solar PV kicks out during the summer. I have no idea really how long it takes to get one..when I chose the company who installed my solar I did so as they were Tesla certified and said they had a couple in stock. If you can afford one I would definitely go for it, you can pretty much get through every day on off peak electricity and of course have it there as a backup if there’s a powercut..plus the app is really cool..it’s nice to be able to swipe between the car and the powerwall.

 

[gangzoom]

Echo what's said above, if you try to justify one on financial basis you cannot, but the tech is extraordinary. Our has been installed since November last year, and in that time between 7am and midnight the Powerwall had powered our house 95% of the time!!

Its a bit like FSD, if you can afford it go for it, but if you analyse it in detail you will see its not really a great way to save money.

On the batteries getting cheaper bit I believe PW2 prices are higher now than in the past!! Just like the cars I wouldn't count on anything getting cheaper for us consumers, I paid £71k for our X in 2017, it looking like a Model Y could easily cost just as much in 2021 .

 

[Barry E]

another echo for the it wont pay back comment
It doesn't make financial sense , but is a great toy if you can afford it and when combined to solar
will for most people mean you use little if any peak electricity so it will slowly reward you , but its not a financial decision to buy one really.

I am constantly tweaking and checking mine in the app

I just wish the app software was smarter and automatically diverted excess solar to the car charger when the battery
is full. Everything necessary is there in the software it needs nil hardware to accomplish this and to be honest probably isnt even a difficult programming task for anyone with the required skills

on a sunny day I manually control charging of the car remotely using the slider in the car charge section of the app to let it charge for short periods to take up the solar but its a crude way to do things.

come on tesla , make it smarter.

 

[Adopado]

I just wish the app software was smarter and automatically diverted excess solar to the car charger when the battery
is full. Everything necessary is there in the software it needs nil hardware to accomplish this and to be honest probably isnt even a difficult programming task for anyone with the required skills

on a sunny day I manually control charging of the car remotely using the slider in the car charge section of the app to let it charge for short periods to take up the solar but its a crude way to do things.

come on tesla , make it smarter.

That's the Zappi charge point USP ... enabling the car charge to coordinate with the solar availability ... and it should actually work once Tesla sort out the M3 responding to an advertised available charge when it's asleep!

 

[InventEd]

It’s a shame they can’t make the car battery be the Powerwall. Basically power your house from your car battery in peak times then let the car recharge for cheap at night (when no one else is using it but the wind farms are still producing. )

I know it doesn’t capture the solar when you are at work but seams something that could be easily done.

 

[henleyregatta]

I've gone for the Octopus deal they were advertising before Xmas, waiting for the DNO to go through to get it all fitted. I'm starting from scratch - no solar yet, just a car and Tesla Wall Charger.

I ran the numbers based on our current consumption and the quoted install costs. With all that, the export tariff and the incentives on the offer I've come up with a 20 year return on investment for the system; well outside the warranty period. This is not a decision that makes financial sense.

I should note we don't have a huge area for Solar and we've not got the best aspect for it either, so we should be on the high end of the modelling rather than anywhere near ideal. But we're doing it anyway, for many of the reasons that are already in the thread - it's a little bit greener way of living, it supports decarbonisation, but mostly it's a bunch of cool technology and i will have hours of fun playing with it.

By the way it's worth checking out Robert Llewellyn's Fully Charged episode about fitting his 2nd Powerwall if you're thinking of this primarily as cover for power dropouts. Near the end he demos a "mains outage" and the system takes a good 20 seconds to switchover to battery. You'll be wanting something a bit more Uninterruptible if you're trying to avoid your electronics going down....

 

[ACarneiro]

Yes, that was interesting and at odds with the experience of many people who have PWs installed. They say the switchover is seamless an not noticeable...

 

[MrBadger]

it's a little bit greener way of living, it supports decarbonisation,

At 20% losses through the system, I fail to see how, except on a few odd occasions, its any greener at grid level. If anything, its a very inefficient way of using electricity compared to normal on grid use.

 

[henleyregatta]

At 20% losses through the system, I fail to see how, except on a few odd occasions, its any greener at grid level. If anything, its a very inefficient way of using electricity compared to normal on grid use.

If the grid was 100% renewable, you'd be correct. As it stands, I see the ability to feed the grid from the powerwall (which is one of the points of the Octopus deal) as making some contribution even if inefficiently - the point being that there's little to no grid-scale storage capacity (OK, there's those hydro dam/lake schemes in Wales and Scotland but they're not scaling with use), so providing "greener" power for the peak period is better than firing up the coal/gas plants to do the same job.

 

[im85288]

Yes, that was interesting and at odds with the experience of many people who have PWs installed. They say the switchover is seamless an not noticeable...

Yes agreed, the switchover for me is seamless with no downtime at all. Not sure what was up with Fully Charged’s installation. When I got my PW2 I really didn’t anticipate needing to use the backup feature but as explained in my post above it’s nice knowing it’s there. The only dilemma I have is how much battery to reserve for power cuts, currently I have it on 5% but most of the time we don’t get powercuts...I know though if I set it to 1 or 2% then a power cuts bound to happen and annoy me for not reserving enough battery!

 

[MrBadger]

If the grid was 100% renewable, you'd be correct. As it stands, I see the ability to feed the grid from the powerwall (which is one of the points of the Octopus deal) as making some contribution even if inefficiently - the point being that there's little to no grid-scale storage capacity (OK, there's those hydro dam/lake schemes in Wales and Scotland but they're not scaling with use), so providing "greener" power for the peak period is better than firing up the coal/gas plants to do the same job.

I had forgotten that the octopus deal was to do with grid balancing. So yes, in this case, it could be a benefit - better than spinning up diesel generators elsewhere at very least.

But for normal energy storage scenarios, time shifting by filling the store from energy when marginal grid source comes from gas (which is most of the time) and being hit by 20% round trip losses, is counter productive. The prime purpose of the likes of Dinorwig is not time shifting, but to do with rapid response frequency control. It sounds like the Octopus trial is that on a very small scale and performing that function at local level, I can see becoming a very important role in the future.

 

[brucet999]

I have 4kW solar PV, with panels on both sides of the roof so peak power is generally a little over 2kW but I get a decent amount of exposure (time-wise). On a typical winter day I might get 1 or 2 kWh, in summer it's often in excess of 20 kWh. Got it installed just before the FIT prices dropped from ~12p/kWh.

Switched to Bulb back in spring last year and am on Economy 7 with a day rate that is twice the price of the night rate.

Recently had a Zappi and Eddi installed. Previously had a Solar iBoost which was happily dumping about 6 kWh daily into the immersion water heater (which is an old tank with very little insulation so that's something I'm looking to upgrade at some point so I'll probably be using less energy to heat it.)

Based on the Myenergi app readings, most of my usage is generally below 500w at all times except for the evening peak when food is cooking, using the washing machine, and of course when charging the car or powering the storage heaters (both of which happen on off-peak rate overnight.)

So far I've always been trying to time things like using the washing machine based on how sunny it is, which can be a bit of a gamble as sometimes it's bright for a bit and then it clouds over.

The Zappi should theoretically be able to boost the energy supplied to my car but there's an issue where the car doesn't wake up when charge is available from a Zappi in Eco+ mode, which is a little annoying.

Occasionally, I've read/heard about the Powerwall. We rarely have power cuts but it'd be nice to not have to worry about that. Being able to store the generated power and use it when it's clouded over or in the evening seems like it'd be making the most of my solar PV. And in winter, importing off-peak energy for use during peak times would save a bit of money.

But of course, it's expensive to buy in the first place. It would probably pay for itself eventually, but only after several years (i.e. probably after the warranty expires!) Part of me just wants it for the tech.

I've seen a handful of posts about it here but I'm wondering:
1. If you have one, what were your reasons for choosing it and how useful have you found it?
2. How long does it take to get one? (I'm hoping it doesn't take as long as a Model 3!)

"…FIT prices dropped…", "Switched to Bulb…" , "…had a Zappi and Eddi installed." , "iBoost"; all further proof that Churchill was right about the US and UK being two great nations separated by a common tongue.

 

[henleyregatta]

Yes agreed, the switchover for me is seamless with no downtime at all. Not sure what was up with Fully Charged’s installation.

Oh - now that's an interesting piece of information. Thanks.

I suspect the main difference between most installations - yours included? - and Robert's is that he had to go to 3-phase power when he added the 2nd Powerwall and (IIRC) he added the Gateway at that time rather than originally. So he won't ever have had the fast-switchover capability to make a comment on losing it. I mean I can't quite see how going 3-phase means there's a long delay in switchover either, but he has a lot of boxes on his wall not just 2 Powerwalls and a Gateway so I'd guess something's interfering with the process?

 

[Barry E]

my powerwall switches off grid seamlessly and almost instantly barely a flicker in the lights , but it's only single phase as I suspect most will be so maybe the delay is strictly a 3 phase issue.

 

[nightowl]

Thanks for all your input.

Power cuts are pretty rare here. I think there has been maybe 3 or 4 occasions where there has been a lengthy power cut since I moved here 9 years ago. I have various bits of computer equipment and a couple of UPS which have been pretty useful when there have been occasional dips in power. I did wonder at first if the Powerwall would serve effectively as a whole-house UPS but some brief research revealed that it does not respond as quickly as a UPS does in the case of a power cut.

During winter, it's obviously cheaper on Economy 7 to power things at night, hence charging the battery overnight would mean cheaper energy during the day. However, given that the cost of the equipment outweighs any of the savings I'd be getting, that's a bit irrelevant. Plus, if overall there's less renewable energy being generated at night time (obviously no solar energy for example!) that would mean I'd be charging the battery off something else and using it during the day, when I could be using grid power that is more likely to be renewable.

Primarily though, it would be nice to actually be able to use all of the solar power I generate - which, in winter, is admittedly not very much. The immersion heater gets a small boost and daytime use of devices is free/cheaper but that's about it.

I have tried to make use of the solar energy at optimal times (e.g. previously used a heat gun to strip some paint when it's a clear day and I'm generating around the same amount of power as the heat gun uses, and I try to run the washing machine when it's sunny) but certain things prevent this - fluctuating amounts of direct sunlight due to clouds, for example! Also if I'm able to store enough energy to be able to run cooking appliances in the evening that would be nice (though I know there's a limit to how much can be output at any one time.)

I'm wary that the cost might rise as well, or that something better will inevitably become available within the lifespan of the product (again probably more expensive though!) Of course, it may continue performing adequately beyond its warranty expires but there's also the chance it could go wrong. The tech aspect of it appeals to me, as would the knowledge that I'd not be drawing power from the grid for a lot of things during summer.

I suppose one way of looking at it financially is that it probably won't pay for itself entirely but at least a portion of it will be paid back by any electricity bill reductions.

Still sort of on the fence about it. If/when I do go for one... How long do they take to deliver?

 

[im85288]

my powerwall switches off grid seamlessly and almost instantly barely a flicker in the lights , but it's only single phase as I suspect most will be so maybe the delay is strictly a 3 phase issue.

Yeah mine is connected to single phase too, it must be something related to the three phase connection. That will teach him to have too much access to power!