But most people don’t need anywhere near a 10kw discharge capability.
So it goes back to the original point of the extra £8k for another Powerwall just not having a payback.
2kwh baseload is something!
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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
So it goes back to the original point of the extra £8k for another Powerwall just not having a payback.
2kwh baseload is something!
Great question.
I am going for 6 panels on south roof, 10 on a west roof, total 5.7kW system with a 3.8 inverter.
Installer said with two roofs, the system will produce more over the day even if some is clipped at midday periods. Maximising power output and making curve fatter at the ends.
david1701
Member
Not sure if this is the right place to ask, but here goes, I’ve recently heard about the Tesla Energy Plan and I think it maybe good for us, so I’m looking for advice, I’ve 6.88 kWh Solar , 3.88 kWh which qualifies for FIT, 2 Tesla Powerwall 2’s and a Tesla Model S, and I’m with Octopus Energy, from what I’ve read so far it seems a little to good to be true, is it ? What does anyone on the Tesla Energy Plan think of it so far ? any help would be great, thanks
I think that what @btc1k is saying is that many wouldn't spend an additional £8k to mitigate just drawing that kettle's worth of power from the grid for the 5 mins it takes to boil a kettle. Although I think your aims are noble
.
We've been on the TEP since 9/2019 and it works as advertised. We like not needing to time-shift our electricity usage and the per kWh rate has saved us more than my rough calculations estimated when we signed on. If you have a deemed export rate on your FIT (I presume you do) you will need to give that up, which I believe is irrevocable. But you keep the generation FIT. In our case, although we were not exporting near the deemed 50% we were receiving a FIT payment for, the TEP savings made giving it up an easy decision. We are a high consumption household, despite my best efforts to reduce our baseload usage, so that plays a large part in our overall savings on the TEP. With only one Powerwall, a relatively small 3.5kW solar array (with some shading issues) and soon to be two Teslas in the family, there was no way we could satisfy our household needs solely relying on the Solar PV and filling the Powerwall with discounted energy in a limited overnight period.
Feel free to PM me with any questions.
WannabeOwner
Well-Known Member
I'm not on TEP. My understanding (quite possibly wrong!) is that:
you can't force 100% Reserve; (other than automatically for Storm Watch) Wifee and I work from home and get a scheduled powercut a couple of times a year (rural here, tree-trimming on nearby roads would cause that, along with other scheduled works to power systesm)
you can't divert excess solar - so basically you are paid to export, and then pay the same to re-import. There is some efficiency loss in that (maybe too little to bother to try to avoid?) but we divert excess PV to charge cars and so on ...
What I'd like is a Time-of-Use tariff where export is in my favour, and then I'll manage the process. Although I can see that Tesla aggregating "all members" should give them the ability to make a profit on the export times (although current process seems pretty crude - from what I read it seems that TWP exports for the evening peak, same time each day). For me that would mean that my PV exports during the day (although I suppose I could charge the car at that time, but not (if I understanding it correctly) using a diverter like Zappi), and for me it would also mean that, because of evening-peak export, my powerwalls would not get me through the night,.
PITA
Model 3 Performance
Which is fair enough. Everybody makes their own decisions...
My examples for needing 10kW discharge to avoid blasting into peak rate are...
- 8kW electric showers x 2
- 7kW induction & 3kW oven for Cooking
- 8kW Heat Pump with 4 internal wall units
- 7kW ev charger directly using Powerwall stored power.
So these 'normal' devices fit inside the 10kW continuous discharge capability of two Powerwalls, so it works for me nicely... keeping me away from peak-rate Grid costs.
Plus 27kWh storage gives me more Solar to actually use for evenings & overnight. Plus cheap-rate stored energy over Winter.
Saving me every drop of power needed. It's perfectly balanced because during Summer I get to run my home with zero Grid Import for week after week.
In the event of a Grid blackout, I can still use all the devices in my home because they'll still work with two Powerwalls. Day or Night.
Which pleased my Wife once, one afternoon as she continued Cooking Sunday Lunch unaware during a street Grid blackout...
... she only found out by questioning my 'Jeremy Clarkson' Smug Face
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david1701
Member
So an extra £8k for another powerwall, to offset the very occasional draw over 5kw, is a very expensive solution.
£8k to offset how much peak grid draw? Let's assume you pull 6kw, twice a day, for an hour. So 2kw a day? 70p?
For sure!Which is fair enough. Everybody makes their own decisions...
My examples for needing 10kW discharge to avoid blasting into peak rate are...
- 8kW electric showers x 2
- 7kW induction & 3kW oven for Cooking
- 8kW Heat Pump with 4 internal wall units
- 7kW ev charger directly using Powerwall stored power.
So these 'normal' devices fit inside the 10kW continuous discharge capability of two Powerwalls, so it works for me nicely... keeping me away from peak-rate Grid costs.
Plus 27kWh storage gives me more Solar to actually use for evenings & overnight. Plus cheap-rate stored energy over Winter.
Saving me every drop of power needed. It's perfectly balanced because during Summer I get to run my home with zero Grid Import for week after week.
In the event of a Grid blackout, I can still use all the devices in my home because they'll still work with two Powerwalls. Day or Night.
Which pleased my Wife once, one afternoon as she continued Cooking Sunday Lunch unaware during a street Grid blackout...
Just in the spirit of the thread, for the majority of people, deciding whether solar "is worth it", then many of these considerations are not really in play.
The "sweet spot" for 95% of people is going to be a modest solar system which offsets a large percentage of peak usage, perhaps combined with a small, cost effective battery system for either excess solar or time shifting to a TOU tariff.
But your example a good one of a "fully electric" case study.
My current blended electric rate is 8.5p, with use of Go Faster, no solar and 1 EV.
Having solar installed next week and a Powerwall in the winter.
TEP has been recommended to me but I will leave it a few months and see how my usage stacks up with the incoming solar etc.
The beauty of TEP has to be that you effectively use every last watt of your own solar generation, with the net metering of 12p in and out.
PITA
Model 3 Performance
Let's just run with your example of 70p per day (35p peak rate)
That's £255 per year. £2,550 over 10 years.
and... you've got the 13.5kWh capacity savings throughout each year on top of that. Be it stored solar, or cheap rate tariff.
13.5kWh per day at 35p = £ 4.72
13.5kWh per day at 7.5p = £ 1.01 stored cheap rate
Saving £1,354 per year. £13,540 over 10 years.
Makes using Heat Pumps very cheap.
... and we're not even talking ROI on free Solar mixed in
I paid £6500 for my second Powerwall, and we use it every single day. So it'll pay for itself.
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RedMod3
Member
I think you will have to do the sums, but I have 5.1kW net solar, and have one and shortly two PWs. I don't export to the grid and my Octopus GO energy costs average under the Tesla rate, so why would I want to pay 12.5p / kWh net when I am paying much less than that on Octopus GO?
RedMod3
Member
I really like this idea as 10kW peak draw would be plenty for me, and having the cheaper Givenergy storage in the background is a great idea.
It is rather like your PC; the CPU has a small amount of ultra-fast expensive memory; the RAM will have more capacity in your PC and is fast, and your disk storage is vast and even slower.
Out of interest, which Octopus Go Rate are you on?
When I did my maths (for my circumstances) Octopus Go was better whilst I am on my current rate of 5p off peak, 13.8 p peak, but when that expires (in Mar 2023) and it moves to the current rates then the Tesla Energy plan would be cheaper.
This is with 1 powerwall and 4.7KW solar
PITA
Model 3 Performance
PITA
Model 3 Performance
I've contacted GivEnergy this afternoon to ask if it can be done.
They think they can't because of how the CT Clamps are set to monitor import and export. But they are interested in the concept and the guy I spoke with (in technical department) will have a ponder over the idea.
I said, if they can 'covertly' integrate somehow to a Tesla installation, people would be interested in a lower cost alternative to storage expansion, without losing their Tesla Powerwall features.
The objective being, the GivEnergy storage would just grab Grid Power at cheap rate and then be responsible for topping up the Tesla Powerwalls directly, either manually or automatically.
RedMod3
Member
PITA
Model 3 Performance
GivEnergy have just come back to me, and they've come up with an idea. So it could actually work.
What they've suggested is the GivEnergy Battery Storage would import Grid Power at Cheap Rate (00:30 - 04:30) alongside the Tesla Powerwalls.
The GivEnergy Batteries would then be tasked to power the Home directly at a set 'base load' amount... like 400watts
This 400 watts would just be continuous for the next 20 hours (8kW) and cover the homes base load. Effectively not calling on the Powerwalls until that 400watt demand was exceded.
This 400 watt baseload could be increased to 2000 watts (like for Winter, as an example)... if any of that 2000 watts wasn't used, it would just get exported back to the Grid (and you'd lose it). BUT... it would provide backup cover leaving the Powerwalls to only get involved above this baseload demand.
So it CAN WORK
... and they appreciated the creativity to it hahaThe only thing they didn't know, is how this baseload power would register on the Tesla App data?
