On-grid domestic battery storage

Solarchaser

I have to say that if you remove the £1500 as a discount, and just look at the system with £1500 off, i dont really see it as a great buy, there are better value buys out there imo.

Unless I misunderstand, and the £1500 is in addition to the buying price discount, in which case its probably better.
I think you said you were around 1000kwh a year, which is more or less £150/ year, so you could get free electric.

All I'd say is that nothing is in stone until its installed, and from your posts the last few days, it sounds like you are having second thoughts.

For myself, I looked at the powervault 8kwh system as I got an email from edf, and worked it out to be more expensive than sofar / lux offerings with pylontech with the £2k discount even before the sharing idea

Solarchaser

Cant edit, read link again, the £1500 is the discount.
If I was you mate, I'd seriously think about stepping back, find a comparative offer without the grid sharing and evaluate your options.

Kev

joefizz

Zarch wrote: »

Just thinking out loud, are there days where you could possibly get more than 4kw out of it each day? Ie you use it through the night, fill it in the morning via solar, midday clouds, dip into battery with washing on etc, sun comes out again, battery fills back up..... then its full again for evening use?

That pretty much sums up a lot of my posts over the last wee while, use it as a repeatable store. So in mornings I get enough with it to run the hot tank immersion heater for water for shower etc, use slow cooker during the day so you dont have to cook at night.
If you like curries consider the slow cooker angle and a japanese rice cooker, very efficient and cooks quickly.
I found the 4.8kw couldnt run my particular immersion heater at low solar times so could have replaced the element with a smaller one or upsized batteries so did that as I could see other usages once I had the batteries installed.
Ive had an ashp lying in my hall for a couple of weeks yet (bought before the 1st april price rises) and going on export figures since my last bill I could easily have run a fair bit of the heating on it with the excess using the battery to smooth it out. Wouldnt have worked last night though as it was -2C here but you will get anomalies like that.
There is a cutover load level on the batteries, so an import level above which they will kick in. I lad low energy led lighting in the bedroom so changed to a warm light led filament bulb with high enough wattage to kick in the load... yeah I know...
I dont have the figures for the larger battery in summer yet but certainly with half my 4kw array facing due east straight to horizon and with normal overnight household load my batteries were full by 8am most summer mornings. Shower, coffee, toast turn on the computer and theyd be full again by 9-9:30 (depending on weather) etc etc.
If you generate say 16kwh on a summer day you can empty and fill the batteries a couple of times so you can learn to use what you have if your schedule allows it.
Of course in Dec they are pretty much useless but then again they made sure I used every single part of that (minus losses) rather than export.

zeupater

Solarchaser wrote: »

...
I think you said you were around 1000kwh a year, which is more or less £150/ year, so you could get free electric.

All I'd say is that nothing is in stone until its installed, and from your posts the last few days, it sounds like you are having second thoughts ...

Hi

Don't seem to remember Zarch making too many posts over the last few days & there aren't too many that have mentioned ~1000kWh/year, but to avoid any foot of the alphabetic table confusion, <cough>, until the battery solutions hit somewhere near the £150/kWh raised earlier, I'll be sticking with my current set-up, as should anyone with a near-typical usage pattern & around/under UK average electricity consumption and expecting a solution to show any form of saving over importing from the grid ...

This Z's still quite content to hold onto a 'first thoughts' solution ...

HTH
Z

1961Nick

I got home tonight & the batteries were full.:cool:

She arrives home about 10 minutes later & immediately switches on the tumble drier, washing machine, oven......and now the hob is on as well.

The batteries are contributing 3.01 kWh & we're importing 5.47 kWh!

It's a battle....(insert rolleyes smiley here).

zeupater

joefizz wrote: »

... I found the 4.8kw couldnt run my particular immersion heater at low solar times so could have replaced the element with a smaller one or upsized batteries so did that as I could see other usages once I had the batteries installed....

Hi

Yet a relatively cheap proportional diversion system for the DHW would likely have a far better payback for most (with cylinder etc) considering the effective cost could be between 10x & 20x cheaper per kWh of storage and would have the additional advantage of removing the round trip inefficiency of the batteries, so likely around 18%-20% (100/x) more thermal energy transfer per kWh of solar generation ...

HTH
Z

joefizz

zeupater wrote: »

Hi

Yet a relatively cheap proportional diversion system for the DHW would likely have a far better payback for most (with cylinder etc) considering the effective cost could be between 10x & 20x cheaper per kWh of storage and would have the additional advantage of removing the round trip inefficiency of the batteries, so likely around 18%-20% (100/x) more thermal energy transfer per kWh of solar generation ...

HTH
Z

Only if you wanted to heat a tank of water, rather than enough for a shower and then use the electricity for something else...
..or just decide with 15 mins notice to have a shower.. or.. or...
Certainly if you need a full tank of water then that would have been the best option, or if you werent paid for actual export but estimated export you could make out like a bandit with the iboost...

joefizz

1961Nick wrote: »

I got home tonight & the batteries were full.:cool:

She arrives home about 10 minutes later & immediately switches on the tumble drier, washing machine, oven......and now the hob is on as well.

The batteries are contributing 3.01 kWh & we're importing 5.47 kWh!

It's a battle....(insert rolleyes smiley here).

Cant help with a lot of that but my washing machine has a timer function and the one before that had a delayed start function....
..so does the oven come to think of it but it depends what you are cooking ;-)

1961Nick

joefizz wrote: »

Cant help with a lot of that but my washing machine has a timer function and the one before that had a delayed start function....
..so does the oven come to think of it but it depends what you are cooking ;-)

The timer function on the WM had been used.....that was the load that went straight into the drier.

Anyway, dinner is now over & the grid is now static......phew.

Total damage 0.65 kWh......the 8.5p won't break me.:D

zeupater

joefizz wrote: »

Only if you wanted to heat a tank of water, rather than enough for a shower and then use the electricity for something else...
..or just decide with 15 mins notice to have a shower.. or.. or...
Certainly if you need a full tank of water then that would have been the best option, or if you werent paid for actual export but estimated export you could make out like a bandit with the iboost...

Hi

Works well as a form of relatively cheap energy storage for many on the forum & would certainly reduce the battery capacity requirement for anyone looking to increase solar self consumption through employing both solutions ...

Did you not consider the option of running two immersions from one controller with priority on the upper one & relying on thermal stratification to allow a single cylinder to effectively have two storage volumes for varying solar generation conditions?

We don't have proportional diversion, but effectively use this type of dual capacity setup to reduce the energy supplied to DHW when solar conditions are poor (almost exclusively Nov-Mar only) ..

HTH
Z