Extra batteries & future system expansion

[richbee]

Is there a general rule of thumb in terms of battery capacity against general use.
Ie if in December/January you use roughly 100kWh a day, average, what would the ideal battery capacity be as a percentage of use?

I don't know - I'm working on the basis that I currently have 5kWh of batteries, which is clearly not enough, and hope that by adding another 5, it will fulfil most of my usage - keeping things topped up from the solar in the summer, and allowing maybe 2/3 from overnight cheap electricity in the winter.
I haven't worked it out exactly, but there will be a point of diminishing returns where you would never get your money back if you spent loads of money on batteries.
When/if I get to the point of having an EV, ASHP etc then it would make more sense to have more batteries (or hopefully using the EV battery will be more common by then)

[openspaceman]

Is there a general rule of thumb in terms of battery capacity against general use.
Ie if in December/January you use roughly 100kWh a day, average, what would the ideal battery capacity be as a percentage of use?

That's an interesting question.

If you are on a good off peak tariff and you do not want to buy any high rate electricity then your usable battery capacity needs to equal your maximum daily usage less daily minimum solar pv production. In the "shoulder months" when solar generation doesn't quite meet needs you need less. In summer you just need enough to cover the occasional rainy day.

I manage with a battery that is about 5/8 of my average daily usage but import 450kWh annually which was about the best capacity-cost benefit

In general I don't think it is worth getting a battery that eliminates import as the standing charge is significant but I do want a bigger battery for the hell of it.

Having a BEV that is away from the charger much of the day will skew the argument somewhat as you can accept a 15% loss in battery to battery charging.

[Krill]

Part of that calculation is also the export rate: if you can be paid more for exporting during the day than it costs to import at night then theoretically there is a benefit to having a battery which covers 100% of your usage and all solar production should be exported. This seems to be the niche Octopus Flux will fill but then there are tax costs.

Although following this logic through, if one was paid nothing for export, but import costs you any positive amount (notwithstanding the occasional negative price point, and there are charging slots with variable charging costs) the eventually one would recoup the cost of the battery but not necessarily the cost of the solar PV system. I think some people have commented that when they did the sums for solar PV it was just better to stick with a battery only system for this reason.

From the sums I've run I think the diminishing returns happen for me after around 100% of daily use which is around 10-12kwh of battery storage but with dual inverters I should be able to charge twice that in a 3 hour cheap slot so I think my scenario might be slightly different to most posters here (No BEV, gas boiler and hob).

Of course all this presumes the grid exists. If one wants redundancy (maximising security over cost) max solar panels and battery stocks all the way.

[Tinbum]

Thanks guys - I'm very impressed - like having a team of private investigators
They do sound a little on the 'inexperienced' side, giving them the benefit of the doubt!

Hope your paying with a credit card!!

[nowty]

Thanks guys - I'm very impressed - like having a team of private investigators
They do sound a little on the 'inexperienced' side, giving them the benefit of the doubt!

Hope your paying with a credit card!!

And something I found out recently, if you pay by paypal (via a credit card) you are not covered through your credit card, but have to rely on the paypal protection.

[Swwils]

You could estimate the battery required based on your previous years use and generation. PVGIS and PVLIB also has similar tools.

[Tinbum]

Thanks guys - I'm very impressed - like having a team of private investigators
They do sound a little on the 'inexperienced' side, giving them the benefit of the doubt!

Hope your paying with a credit card!!

And something I found out recently, if you pay by paypal (via a credit card) you are not covered through your credit card, but have to rely on the paypal protection.

I had that experience a few years ago when I bought a car with paypal and the seller took the keys off me and wouldn't let me leave with the car. I got no joy with the police, ebay or paypal but my credit card did refund me.

[nowty]

Hope your paying with a credit card!!

And something I found out recently, if you pay by paypal (via a credit card) you are not covered through your credit card, but have to rely on the paypal protection.

I had that experience a few years ago when I bought a car with paypal and the seller took the keys off me and wouldn't let me leave with the car. I got no joy with the police, ebay or paypal but my credit card did refund me.

You may have been lucky, it seems to get complicated. I don't have any personal experience myself.
https://www.moneysavingexpert.com/credi ... Section75/

[Tinbum]

Yes I think I did.

[Adrian]

This is their registered company address in Crawley,



Hi
I understand some of you may have some concerns about the website.
To keep the cost down for the business we decided to keep our home address as the registered business.(this will change)
I appreciate the website design is not the best and there may be some things to work on, but again to keep the cost down and offer better prices we have designed the website ourselves.
The phone number is on the website and was always on the invoices sent to our customers.
There is a chat box available on the website and also a FAQ page, again the reason is to keep the cost down and offer better prices.
Yes, we are small family run business and we started this journey less than a year now but we have many happy customers.
We are working with some of the biggest suppliers in UK and we always trying to offer the best prices for our customers.
Happy to answer any questions, but please don't post a photo of my house unless you had any problems with the business.

Many thanks
Adrian
DSWS.SHOP