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Wait for Powerwall or go for alternative? High electric usage

 
Energy Storage
Last Post by Benseb 3 years ago
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 Benseb
(@benseb)
Reputable Member Member
Joined: 3 years ago
Posts: 109
Topic starter 20/08/2022 5:07 pm  

Hey everyone

 

We are a fully electric house. Plus we have a holiday let attached to our supply. 

Last year on some days in Jan we pulled over 120kWh of electric in a day. Approx 60kWh for ASHP then the rest split 50/50 between house and holiday let. 

Im going to do some work to hopefully optimise the ASHP consumption. But as we have PV I’d also like to explore batteries and charge them on our aoxtopis Go Faster 5 hours at 8.25p

 

i placed an order for a Powerwall back in March but still don’t have a date. Just a few emails saying they were very delayed. I don’t think it’s going to arrive this year. 

alternatively I’ve seen systems such as Solax which give you 25kWh for about £15k (Powerwall is about £9k)  so about the same price per kwH

 

Has anyone any experience of Powerwall vs other systems? Is it really much better or is that just branding?

 

 

 

 

250sqm house. 30kWh Sunsynk/Pylontech battery system. 14kWp solar. Ecodan 14kW. BMW iX.


   
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 batalto
(@batalto)
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Joined: 4 years ago
Posts: 1091
20/08/2022 7:43 pm  

Apart from the control system and app, they all do the same thing. You can build a 15kwh for about £2.5/3k with cells and a BMS box. Also worth noting that a powerwall uses lithium ion cells like a car, most other batteries use lifepo4 batteries (which are heavier, but far more stable)

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE


   
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 ChickenBig
(@chickenbig)
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Joined: 3 years ago
Posts: 292
24/08/2022 8:11 am  
Posted by: @benseb

Is it really much better or is that just branding?

If you have a Powerwall and solar panels then you can sign up for the Octopus Tesla plan which is currently around 26p/kWh plus 45p/day standing charge and is symmetrical. Note that the price used to be much lower, per post in April this year, so the price rise does indicate that the Powerwall is more defined contribution rather than defined benefit.


   
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 Benseb
(@benseb)
Reputable Member Member
Joined: 3 years ago
Posts: 109
Topic starter 24/08/2022 8:22 am  
Posted by: @chickenbig
Posted by: @benseb

Is it really much better or is that just branding?

If you have a Powerwall and solar panels then you can sign up for the Octopus Tesla plan which is currently around 26p/kWh plus 45p/day standing charge and is symmetrical. Note that the price used to be much lower, per post in April this year, so the price rise does indicate that the Powerwall is more defined contribution rather than defined benefit.

Yes to be honest when it was 11p/11p that was our main reason for wanting a Powerwall. Running the ASHP at 11p wouod be amazing

 

Now it’s 26p the shine has gone. We’re on Go Faster at 30p/8.25p so currently that’s cheaper overall. 

Will see how things go in the winter but I think the main priority is any battery over no battery! Don’t think there’s a chance of the powerwall arriving before 2024. 

250sqm house. 30kWh Sunsynk/Pylontech battery system. 14kWp solar. Ecodan 14kW. BMW iX.


   
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 ChickenBig
(@chickenbig)
Honorable Member Member
Joined: 3 years ago
Posts: 292
24/08/2022 8:50 am  

@benseb

120kWh of electricity a day is rather high; a reasonably sized battery would struggle to make a dent in the bill from this. To what extent have you tuned the ASHP settings? Also how much of the non-ASHP usage is for your cars and how much for domestic?

DIY storage costs alone are approximately 2700 USD for around 14kWh (e.g. a Seplos Mason for 500 USD with 16x 280Ah batteries for 2200 USD). Assuming 90% efficiency you are looking at £2.70 a day of savings from this battery, so 2 1/2 years to break-even. I've not been following vehicle-to-grid posts on this forum as I'm not a car owner ...


   
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 Jenny@ross
(@jennyross)
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Joined: 4 years ago
Posts: 63
26/08/2022 12:33 pm  

We are also fully electric (9,000 kWh per annum) and also placed an order for a Tesla Powerwall in March and are not expecting it to arrive until 2023.

 


   
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 Diverted.Energy
(@diverted-energy)
Estimable Member Member
Joined: 3 years ago
Posts: 64
27/08/2022 7:41 pm  

Don't know your usage and demand, but:

Although 120kwh per day, it is not technically 120kwh from battery as while sun is shining and you have enough panels.  You'll be charging the batteries for nighttime and running loads direct from the Inverter and Solar, so in theory - 60 to 80kwh batteries would suffice.

This is similar to a project I am currently working on.

Oversize the solar to charge and power then run the batteries down overnight or during heavy loading.

Don't oversize battery/Solar that payback is long, there is a balance where some Grid is OK as chasing 100% Solar / Battery would be inherently expensive.

Aim to do the heavy stuff on sunnier days and around 11am to 2pm if possible.

I can explain further if needed..

 


   
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 Benseb
(@benseb)
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Joined: 3 years ago
Posts: 109
Topic starter 27/08/2022 8:06 pm  

That’s our winter load so very little PV at that time.

 

in the summer we only pull about 15kWh from the grid without batteries due to evening meals etc that are difficult to shift. Now we’re on Octopus Go the cost of that is minimal.

So not really much way to reduce battery need in Winter. I think we’ll get 20-30kW to reduce things down a bit in winter as we don’t want a huge expensive array that’s useless in summer. 

250sqm house. 30kWh Sunsynk/Pylontech battery system. 14kWp solar. Ecodan 14kW. BMW iX.


   
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