Back on the self-build waggon...

Given the likelihood of power cuts in severe storms, the increased risk of severe storms over time, and the fact that our passive house will be electric only, we have started thinking about installing a battery to use as backup in the event of a power cut. 
We’ve not planned to fit any solar panels (the cost v savings don’t justify this) but may do if it becomes economic. 
Following your thread with interest. 

3.5kwh is a good start, really need at least 10kwh of storage to be able to take advantage of time shifting electricity tariffs.

 

3.5kwh storage cost £857 per KW/h

 

tesla powerwall at 13.5 KW/h capacity is much cheaper at £488 per KW/h

 

I looked at all the options in 2018 and Tesla couldn't be beaten on price/kwh, really needs a simple alternative that batteries can just be added to cheaply.

43 minutes ago, Omnibuswoman said:

Given the likelihood of power cuts in severe storms, the increased risk of severe storms over time,

The worse power cut I have had lasted 4 hours. That is in over 20 years. And that was caused by a digger.

It is not really third world down here.

Waiting for this Eunice to do here worse, not too bad at moment and the tide us now on way out, so flooding risk is dropping rapidly.

 

Not many power cuts round where I am either, have had the odd one over the years, but nothing more than a minute off, so I didn't have the backup socket wired in, though I could do that myself later down the line.

 

Yeah the Tesla Powerwall is absolutely the best value for money, but for me that amount of storage is just far too much.

 

Yesterday had the washer on, dryer afterwards and cooking my dinner and tea, and used very little from the grid. Export has now dropped to zero, haven't exported anything since it got installed, and also have managed a full charge yet, just not been sunny enough. Worth noting that because i'm on a deemed export tariff for the Solar FiT, I'm still being paid for 50% of what i generate as a deemed export, even though nothing is going out at the moment.

 

 

One thing I did notice last night when cooking (around 18:00) was that the battery storage inverter couldn't react quickly enough to cover the induction hob, which pulses, so it drew around 800W from the battery, but it was still importing around 100W from the grid, so worth taking into account, wasn't something i'd even thought about.

 

At present the battery is drained before I head to bed, this will alter as the days get longer, and this led to another discovery. So the inverter is set to not discharge below 10% SOC, however the battery does still discharge very slowly, but what i've seen is that it tops up a little from the grid through the night, and then discharges that to loads, the little and often bump on the graph through the night is the fridge freezer.

 

Cost per kWh - £2450 / 3.3 (usable) = £742

 

Very happy with the 3.5kWh Battery at the moment, thinking what I would gain from another 2.4 may be minimal, but will see how this evolves.

Edited February 18, 2022 by MikeGrahamT21

I’ve been thinking about you guys down there and wondering how you were doing. Glad it’s not too bad so far.

 

I’ve definitely been influenced by the horror stories of Storm Arwen and people up north being without power for days or in some cases weeks. The water supply here went down a month ago for the best part of a week, despite SWW’s best efforts.

https://www.bbc.co.uk/news/uk-england-devon-60098358?fbclid=IwAR1_s1xOMHEd6UBFR3ZcqB-r4mVqaFmrbiiAHUEPMwgkU53bLlcymOwYHk4 (Out of interest, the woman in the picture is our least favourite neighbour - she left her broomstick at home for the BBC interview) 

 

I guess I’m anticipating a greater frequency of severe storms heading our way in the coming decades and the increased likelihood of damage and supply issues.  We will keep an open mind for now, but interested to see if the battery saves Mike some ££. 

Stay safe! M

Yes blowing a Holley down here, where I am is windy normally, very flat from the coast only a couple of miles away, I tied the garden furniture down last night ?‍♂️(I think @SteamyTea has been blown away).

13 minutes ago, joe90 said:

SteamyTea has been blown away

It is comic day.

So ignored all advice and gone out. Unlike the post sorting office that is closed, with my parcel in it.

 

Highest gust at Southampton dockhead so far today is 78.1 knots (89.9mph) and tidal surge is 94cm above expected, and still about an hour to the first high water (we get double highs in the Solent).

And gobsmacked to see a guy working inside this in the last hour...

 

 

3 hours ago, SteamyTea said:

The worse power cut I have had lasted 4 hours. That is in over 20 years. And that was caused by a digger.

It is not really third world down here.

Waiting for this Eunice to do here worse, not too bad at moment and the tide us now on way out, so flooding risk is dropping rapidly.

 

Our recent record is 4 days.

4 minutes ago, Triassic said:

Our recent record is 4 days.

How many years/decades have you lived in that area?

5 minutes ago, SteamyTea said:

How many years/decades have you lived in that area?

Around a decade.

 

We get power cuts around twice a year. Mainly less that a day. The last one,  the third in twelve months,  was last week and lasted for 16 hours. The biggest pain is reprogramming everything that isn't 'smart' enough to have a memory.

3 hours ago, joe90 said:

Yes blowing a Holley down here, where I am is windy normally, very flat from the coast only a couple of miles away, I tied the garden furniture down last night ?‍♂️(I think @SteamyTea has been blown away).

There’s no scream face emoji so I had to choose the sad face one to convey my concern about @SteamyTea Hope you’re ok Tea. 
 

My mum said there are several trees down near them in West Devon. 

5 minutes ago, Omnibuswoman said:

Hope you’re ok Tea

Really has not been that bad here.

We are used to 100 MPH winds, though not had any recently.

As the wind was predominantly from the West, app the ports are sheltered, they they are built that way around.

We have just had our power restored, been off since Friday night, a large tree landed on the small substation ?‍♂️

5 minutes ago, joe90 said:

We have just had our power restored, been off since Friday night, a large tree landed on the small substation ?‍♂️

Seems most of the problems near me have been caused by fallen trees. 

Not as if WP did not have enough warning.

3 hours ago, joe90 said:

We have just had our power restored, been off since Friday night, a large tree landed on the small substation ?‍♂️

 

Crikey! That's a long time to be without power. Hope your freezer contents are ok

1 hour ago, Omnibuswoman said:

Hope your freezer contents are ok

Trying to eat  through it now ?

Trick is to not have a freezer.

I have managed without one for decades.

Tinned and dried food is the way to go.

I can't imagine doing without a freezer, Tea. We use ours every day. We were planning to have two in the new house!

8 minutes ago, Omnibuswoman said:

I can't imagine doing without a freezer, Tea. We use ours every day. We were planning to have two in the new house!

 

We've had an identical pair of freezers stacked next to a tall fridge in our kitchen for over two decades now and apart from the electric costs they've proved to be very handy. When we built the house it was the only way to get a decent capacity out of a vertical format. Being ancient they do require regular defrosting (about once a year) but they get done one at a time, shifting the food between them.

my answer is simpler and cheaper 

 I have a small  4kw generator which I can  connect to the house --turning off the incoming  mains first of course

feed it back in the ring main and it will run every  thin but the elec cooker

 over 30 years never had an outage more than a few hours  and watch for street lights coming back  on in the town 

Edited February 25, 2022 by scottishjohn

On 18/02/2022 at 08:29, Dave Jones said:

3.5kwh is a good start, really need at least 10kwh of storage to be able to take advantage of time shifting electricity tariffs.

 

3.5kwh storage cost £857 per KW/h

 

tesla powerwall at 13.5 KW/h capacity is much cheaper at £488 per KW/h

 

I looked at all the options in 2018 and Tesla couldn't be beaten on price/kwh, really needs a simple alternative that batteries can just be added to cheaply.

I disagree with this at current prices. I have been quoted £9500+VAT for a PW2 installed. if we ignore VAT as I'm a new build that would be £703/kWh.

 

And with a system like @MikeGrahamT21's (and what I'm considering) the price per kWh gets cheaper with the more storage you add as quite a bit of the cost is the inverter. so if he adds the US2000C adding 2.4kWh to his storage array his £/kWh goes down to £542. it's why I can't justify a PW2 at the moment. oh....and the 9 month lead time on the PW2 units!