On-grid domestic battery storage

Martyn1981

shavy65 wrote: »

Well I`m none the wiser. I`d be more than happy to let you decide for us Mart :cool:

Oh cripes, time to run away and hide.

I'm not sure about the irony factor of discussing just myself spending too much on a batt for fun on a MSE site, but ethics would also go out the window if I helped others do it too!!!!!!!!!

Exiled_Tyke wrote: »

Well I'd be up for it although like you I'm not overly optimistic that it would be viable. I'd be wanting something which made best use of my SolarEdge inverter.

Yep, same again, won't be tomorrow that's for certain.

I've read that batts have halved in price over the last 5 years, so could mean it could possibly half again in another five, or faster as the market explodes, or perhaps never if the curve starts to flatten out. Well that was inspiring.

I'm just wondering if there's a massive mark up in the price from the installer, and that's not a criticism, as they may do next to no installs, so the whole thing is a royal pain in the butt at the moment. So my brain pondered its way to a multi-install deal ..... who knows?


In the meantime, I've noted an interest with a few of the bigger names just to get my name on the books in case they or the DNO decide on some sort of trial, you never know.


Back to battery sizes, if anyone wants to have a ponder with me, then I'm happy to play with the numbers and present a 'reasoned' argument, but this could be the blind leading the blind.

Starting requirements would be estimated import, export and generation for each month, or maybe just a rough guess for the Nov-Jan, Feb-Apr/Aug-Oct & May-Jul quarters. From there we can probably guesstimate (make up) something.

Perhaps a new section for the FAQs, though I suspect at the moment it would just be a referral to this thread and the line "I dunno, why you asking me?"

rugbyleaguesmate

Thanks for this Mart, still a newbie here with my panels, still producing a lot more than I use and still thinking what I could do with the excess........

Random thoughts radiators, electric car, air conditioning/heater, water (although I have no tank and a combi)

Still think battery when the price is viable.

Question would you think a battery becomes more viable with a bigger system? My logic being you can produce and store more even on low kw days?

What I'm thinking is I probably consume more than you and may produce more, what price break would make a battery viable? You have guessed £1500 I'm wondering if I would be at a slightly higher number for me?

Martyn1981

rugbyleaguesmate wrote: »

What I'm thinking is I probably consume more than you and may produce more, what price break would make a battery viable? You have guessed £1500 I'm wondering if I would be at a slightly higher number for me?

Hiya. Assuming you generate more, use more, and (safe bet) produce more in the winter when my E/W system suffers most of its loss v's south facing - then I'd also guess that you'd get greater benefits from a larger system than I.

For arguments sake, let's double your potential v's mine, I think this is a reasonable bet:
Summer - I import 2.5kWh's per day on average, but have tons of export. I assume you also have no shortage of export, and possibly import 5kWh, so a 4kWh battery would probably suffice.

Winter - I export 1-2.5kWh per day on average. I assume you'll be closer to double that, so again 4kWh batt should do.

Spring/Autumn - I import 4-5kWh, with enough export to cover that. I assume your generation is higher, and your consumption, but this is the crucial guess, I also assume your import is higher than mine, but you have enough export to cover it, say 8-10kWh per day? That would suggest to me a batt of about 7-10kWh.

So your breakeven (not necessarily profitable, viable (after lost interest) or sensible) may be £3k over 10yrs. But economies of scale are on your side.

The Tesla Powerwall II costs £6.3k installed for about 13.5kWh. Proportionately, that's not far off for you (in this theoretical example). And it's reasonable to think that prices will fall soon to a point where a half sized batt, at half that price may be available.

For myself, whilst 4kWh/£1.5k is also similar to the PWII price, it's also sensible to assume that it will take longer for a product to match my specs as there will be some fixed costs such as the case, shipping, install, management software/hardware.

Actually, if I've got these numbers right, then for those that could make use of a larger batt, we are closer than I'd thought. But bear in mind my £1,500 figure includes about £300 in savings from shifting to a NSC tariff, which may not work out for higher users if their import still remains large even after the battery.

If this seems confusing, or you think I've got a solid grip on it, then please believe me, I don't. I'm really just thinking out loud.

One other consideration relates to the ASHP thread - lots of if's here so hold on ...... IF it makes sense to use a heat pump instead of GCH, and IF I have enough export available to justify a bigger battery, and IF a heat pump warming one room, but flowing into the rest of the house can match a short GCH burn - then it might make sense to opt for that via a battery coming on a few hours earlier in the morning during those months when solar gain is adequate later on, but the house is a tad too chilly in the morning to switch the heating off.

I can't work this out, but for me it may only work in April and Sept when heating might not be needed some years, so a waste of battery capacity?

Martyn1981

rugbyleaguesmate wrote: »

Question would you think a battery becomes more viable with a bigger system? My logic being you can produce and store more even on low kw days?

Just realised I may have interpreted your question wrong. If you were sticking with the same size battery as me, say 4kWh (useable), which should provide about 5kWh across the day (including mini-cycles), then it's safe to assume you would use its full potential more than I.

I'm estimating I could get 900kWh's out of one per year, but you might get 5kWh's per day most days, and even if we aim low for winter with 3kWh's that would give an annual 'import-avoidance' of ((91 x 3) + (274 x 5)) = 1,643kWhs, which at 12p/kWh = £200pa or £2k over 10yrs.

zeupater

rugbyleaguesmate wrote: »

.... Question would you think a battery becomes more viable with a bigger system? My logic being you can produce and store more even on low kw days? ...

Hi

The issue as I see it is that generation, consumption and storage are all components of the same solution ... the problem is that you need to self-justify investment according to your own requirements.

For example, you mention the heat-pump .... the way I see it is that the heat-pump can effectively be run 24x7 when the ExcessGeneration+AvailableStorage+HeatDemand equation is satisfied ... this way you better justify the investment in all three technologies. The issue at the moment is that although any potential return on investment for the solar pv or heat-pump can undoubtedly be improved through the addition of battery storage, the current capital cost of that storage totally destroys the overall investment equation.

We've gone down the (small) heat-pump route in the knowledge that we can deliver additional warmth comfort through supplementing existing heat sources (GCH & Biomass) as generation & heat requirements dictate .... this obviously places us in a position where we would be able to better justify storage when fully installed prices become more favourable, however that still looks to be well below £150/kWh of usable storage for a unit with a decent cycle life ...

HTH
Z

ASavvyBuyer

Not sure if this has already been posted before, but found this on the RECC website:

https://www.recc.org.uk/pdf/guidance-on-battery-storage.pdf

Could be useful for anyone considering buying a battery system and what info should be provided.

Exiled_Tyke

ASavvyBuyer wrote: »

Not sure if this has already been posted before, but found this on the RECC website:

https://www.recc.org.uk/pdf/guidance-on-battery-storage.pdf

Could be useful for anyone considering buying a battery system and what info should be provided.

Your link didn't work for me. This did though.

https://www.recc.org.uk/pdf/guidance-on-supplementary-solar-pv-equipment.pdf

Also, and interestingly the paper suggests that we will be moving from deemed to actual export with smart meters. This is the first I've heard of this. Every other time smart meters have been mentioned I've always heard that same story, which is that they are only being used to measure import and so are of no benefit to us for export. If export metering goes ahead then for battery storage to pay for itself then costs will need to come down to about a quarter of what they are today, unless of course we are all forced into demand led pricing for import in which case they may well become viable at a higher price.

ASavvyBuyer

Exiled_Tyke wrote: »

Your link didn't work for me.

Sorry, somehow there was a missing ":" in the actual link, even though it was showing.

It should be:
https://www.recc.org.uk/pdf/guidance-on-battery-storage.pdf

ASavvyBuyer

This may be a daft question and not even sure if this would work, but has anyone tried using a UPS (Uninteruptable Power Supply) normally used for PC equipment, as "Domestic Battery Storage" for alternative relatively low power equipment?

For example; charging it up during the day, (from solar power) and then using it to power a LED TV or LED lighting during the evening, with power switched off at the socket.

The payback time may make it not worth it, but there are some smaller UPS's available for under £100 which may store enough power.

Martyn1981

Exiled_Tyke wrote: »

Your link didn't work for me. This did though.

https://www.recc.org.uk/pdf/guidance-on-supplementary-solar-pv-equipment.pdf

Also, and interestingly the paper suggests that we will be moving from deemed to actual export with smart meters. This is the first I've heard of this. Every other time smart meters have been mentioned I've always heard that same story, which is that they are only being used to measure import and so are of no benefit to us for export. If export metering goes ahead then for battery storage to pay for itself then costs will need to come down to about a quarter of what they are today, unless of course we are all forced into demand led pricing for import in which case they may well become viable at a higher price.

For myself, I currently export about 900kWh pa more than I'm paid for, so it wouldn't reduce my export income v's today, but if my export was to be metered, the storage would reduce my potential of getting more export payments in the future.

Then again, don't forget the Aussie model that's already in use where domestic battery owners can sign up, and the 'company' negotiates a sale price for stored leccy during peak times, sometimes as high as AUS$1/kWh (when spot prices hit AUS$1,400/MWh). In that situation many of us might be happy to sell/discharge our batts onto the local grid during evening peaks - though it's probably the case that UK spot prices would be peaking in the lower generation months when we may not have much to sell.

This subject ain't getting any easier. :think: