Solar Together

[Newroad]

Hi Paul.

You may be right re a positive bias below.

Hi All.

I think to go off gas one would want to increase the battery storage. Still wouldn't cover the lot, but would almost certainly ensure inter-day coverage when the previous one was sunny.
Regards, Newroad

The recent sunny spell might be giving you false optimism. Twice in the last week my system shows more generation in one day than my total for December.

Paul

However, I still think the facts are broadly supportive. Today, we started feeding into the grid before midday (i.e. the battery had fully charged from where it bottoms out, about 15%, to 100% by then) and stopped doing so just after 5pm. We have just under 11 hours daylight today. At the summer solstice it will be almost 17 hours. I think three of these batteries could comfortably be filled on sunny days a couple of months either side of the solstice at least (excluding EV and/or heavy air-conditioning use).

Like many things, e.g. lanes of traffic and lavatories in a house, I think the marginal benefit reduces with each incremental addition. In this case, my educated guess remains that a second battery 10.3 Kwh battery would be of considerable benefit if going "off gas" but that a third might struggle to justify itself.

Regards, Newroad

[DrFfybes]

Like many things, e.g. lanes of traffic and lavatories in a house, I think the marginal benefit reduces with each incremental addition. In this case, my educated guess remains that a second battery 10.3 Kwh battery would be of considerable benefit if going "off gas" but that a third might struggle to justify itself.

Regards, Newroad

If going down that route you really need to consider the solar and the battery as seperate systems. It took me a few weeks of observation and tinkering before I realised this. The battery is solely to store cheap electricity for use whenever it is more expensive. Whether that cheap electricity comes from the solar panels or a variable tariff with cheap periods is immaterial. So if you can charge the batteries at the same price or less than you get for export, it makes sense to charge them from the mains. If it starts the day fully harged then you simply start exporting earlier.

I would suggest using the existing setup over a winter to get a proper feel for how it works and how you can best use it. New tariffs are coming out all the time, the one I'm on now was not available 12 months ago, and no doubt they will change again. If you have a BEV and can charge overnight at 7p or so then that will be the cheapest way of charging a domestic battery as you should get more for solar export.

Similarly the 'smart' water heater add-ons, iboost etc, were great if on a FIT or jut have panels, but if you have a battery it doesn't matter if you put excess solar/cheap energy into the hot water, or store it in the battery and then heat the water on a cheap timer from 6-8am.

We started with 5kWh battery, it lasted until mid evening in most cases throughout winter and charged overnight on cheap rate. Doubling it to 10kWh meant it would nearly always last until midnight during winter. Over Xmas I moved to a ASHP tariff, 3 cheap periods scattered throughout the day, so now it only really needs to last 4-10pm and rarely gets below 30% - cooking uses as much the multisplit does for heating.

We still have gas and use the CH for 90 min morning and evening, the rest of the day the multisplit copes, but doing this AND switching hot water to electric has doubled our daily use to 20kWh or so. Which is about our total generation for December, so you need to charge from or use the mains so back to 'if your battery will last you 24 hours then it is big enough"

Paul

[Newroad]

Hi Paul.

I mostly, but not entirely, agree.

I think you need a basic battery setup to make the most, in a Pareto Principle sense, of any decent sized solar panel setup. Without one, you can charge an EV perhaps (which is slow and takes time) but otherwise your "point usage" is limited by point in time solar capacity. In this sense, I think it is unwise to disaggregate the solar and battery systems.

Other than that though, I take your broad point. There are other combinations and variables at play.

What I would further note, though, is that your own solar and battery are the two things, that for practical purposes, you can control. Tariffs and whether you can use cheap electricity without a car etc are subject to tariff/legislative risk (in an extreme case, so is solar generation itself). If tariffs continue to go in the "right" direction, i.e. more flexible, then your point becomes stronger. But it could go the other way.

Regards, Newroad

[flyer61]

I have been offered the same again battery 10.3kw for £2700 with Grant store. Eonext in their solar package have a 5.1Kw for £4K.

Any thoughts on storage, price, upside, downside etc?

[DrFfybes]

I have been offered the same again battery 10.3kw for £2700 with Grant store. Eonext in their solar package have a 5.1Kw for £4K.

Any thoughts on storage, price, upside, downside etc?

Flicking back, is this an add-on to your existing battery and would simply slot in?

It depends on your use and tariff. Firstly you need to look at your daily electricity consumption, both summer and winter.

The purpose of the battery is to store your cheap electricity until you get to the next cheap period. This means that in summer it needs to last overnight. However in winter the main benefit of a battery is charging on cheap rate electric, as solar production drops very low from Oct to Feb. If your existing battery capacity is adequate to get you between cheap charging periods then a second battery will have minimal benefit.
Average electric use is apparently 8-9kWh.day in the UK, so financially anything over 10kWh will not be of much benefit to most people.

Previously we had cheap overnight electricity for 3 hours on a 5kWh battery. In winter it just about made it to teatime so I bought a second battery which meant it lasted until nearly midnight.

Currently we're on 'Cosy' which has 3 cheap periods so topping up a battery regularly is simple. We have 10kWh of storage and it rarely gets under 30%.

During the cheap periods we also heat the water on a timer and use the dishwasher/washing machine. Bear in mind that for the time your battery is 'flat' you're only losing the difference between your charging cost and the regular price anyway, perhaps 10p/kWh. For us this year that has been a total of £3.10 used at standard rate, much of which will have been when we exceeded the 5kW the battery can supply (eg oven and kettle on together).

Then there is the issue of charging it - our inverter has a cap on mains charging of 3kW (but 5kW from solar!), so during the 3 cheap electric hours it never fully recharged if it had hit the 5% minimum. No point in being able to store cheap energy if you can't get it in the first place.

Now if you have a system which provides offgrid backup and you expect to make use of it then a second one might make sense as it gives you more headroom, but for the average house using it for cooking and maye hot water then the financial benefits will be very small compared to the outlay.

Paul

[flyer61]

Thanks Paul,

we use 5700Kwh of electric a year but not sure of the winter/summer split. I expect this to increase when I change some bathroom radiators to electric. So on average we use 50% plus more than the average household. We are not on any deal for cheap night time electric but this is something I am looking into. It is just a straight forward add on in series with the other 10.3KW battery.
I'm tempted to get it because if the grid goes down we should have 24 hours plus left to keep things going.

[DrFfybes]

Thanks Paul,

we use 5700Kwh of electric a year but not sure of the winter/summer split. I expect this to increase when I change some bathroom radiators to electric. So on average we use 50% plus more than the average household. We are not on any deal for cheap night time electric but this is something I am looking into. It is just a straight forward add on in series with the other 10.3KW battery.
I'm tempted to get it because if the grid goes down we should have 24 hours plus left to keep things going.

You should look at a variable tariff -
Our total electric spend for the last 12 months has been under £400 inc £180 standing charge, approx 4.9MWh including using the multisplit for heating. 4MWh import, 2.5MWh export. Our first winter was with 5kWh battery and we spent over £200 at standard rate. Over the last 6 months with 10kWh battery we spent £18 at standard rate. so even our second 5kWh battery only saves us circa £80/year and really wasn't worth bothering with financially.

I don't see a mains changeover unit on your installation list - was this done separately? By default if the supply goes down the Solar/battery switches off.

Paul

[flyer61]

The switchover is being installed next Wednesday. So we should be able to cope if the grid goes down.

[the0ni0nking]

All very real now as I try and do some conference calls while the scaffolders are making an absolute racket outside putting up the 3 storey scaffolding.

Scaffolding up for 10 days from today (so comes down on the 20th) with the actual solar panels etc getting installed 13th/14th.

And then I fly back to Spain on the 25th by which time I'll have hopefully sorted everything out with British Gas as they are my current provider and I should move across to their SEG tariff as part of this.

https://www.britishgas.co.uk/energy/gas ... ariff.html

[Newroad]

Hi Flyer61.

Is the "switchover" the addition of an additional battery, or something else?

Regards, Newroad

[flyer61]

It is the ability for the system to continue on independently if the grid goes down. Scaffold moved yesterday, 6 more panels today. Electrics tomorrow including extra battery installation. Will report back once the whole is up and running.

A lot swirling round in my brain after the first 12 days of operation! We have been 56% self sufficient so far.

[the0ni0nking]

Well, I now have 15 panels on the roof after the installation today.

The "team" that did the install were Polish and efficient; all done inside of probably 7 hours - I discussed with their on-site manager whether they could put the battery etc in the garage - and while we both moaned about it; he was categorical that he couldn't put it in the garage as the requirements (not per fire reg but per the contract that Solar Together/Solar Bureau had with Leeds City Council) prevented it.

One of the gentleman who was working on the roof asked to use the toilet - and when he reached part of the house which was carpeted (as opposed to laminate), he took his shoes off and walked in his socks to the toilet. I only mention that because it reminded me of days gone by when that polite piece of behaviour was customary when visiting anyone elses house and sadly seems to have fallen by the wayside.

Apparently, a random number of installs are subject to on-site inspection so while he would have been happy (and agreed that the garage was the best location both in teams of ease of install and security) it couldn't be sited there as it would cost him his job if mine were one of the ones inspected by the council.

What he did say, was wait a month and then ring me and we'll move it - in my mind that sums up the lunacy of what the Council have chosen to do. He also said if that he'd positioned it where we agreed to put it, it would be nicked within a couple of weeks where he lived. I think I'm fortunate to live in a better area(!) and have 2 CCTV cameras covering the install in any case as well as it being in a 6 house cul-de-sac so no passing traffic.

I also rang my home insurers and they confirmed that the panels and battery etc were covered with no extra irrespective of where the battery etc was sited.

Am yet to pay the balance and that I understand will mean they provide the MCS etc details to enable me to advise British Gas but I could see the panels on both side of the roof were generating this afternoon per drilling into the display on the battery.

Hopefully all gets sorted in the next day or so and I can fly back to Spain with both this sorted, and lots of the estate management sorted of my late father.

[DrFfybes]

we had an electrician in yesterday first fitting the kitchen, He does a lot of Solar installs and car chargers.

he says garages and lofts are the norm for battery installs, and was blissfully unaware of the new Guidance/Code of Practice for battery location. He looked it up and was aghast - "so you can have a car with a massive battery on charge in your garage, or with 100l of fuel in it, but not a domestic battery?" which was pretty much my thoughts.

Paul

[the0ni0nking]

we had an electrician in yesterday first fitting the kitchen, He does a lot of Solar installs and car chargers.

he says garages and lofts are the norm for battery installs, and was blissfully unaware of the new Guidance/Code of Practice for battery location. He looked it up and was aghast - "so you can have a car with a massive battery on charge in your garage, or with 100l of fuel in it, but not a domestic battery?" which was pretty much my thoughts.

Paul

The phrase the guy in charge used began with an F and ended with stupid along with a few other choice words. I think his statement was along the lines of "You want it there, I want it there but the F stupid people who can cost me my job don't want it there".

Total insanity - and in some cases, I think people would not go ahead with an install. Congratulations government regulations (no idea whether the requirement was in existence before the Tories or from Labour or just a requirement to be part of the scheme initiated by the local mayor - either way it's a shambles when one can park a car with a bigger battery in the garage every day if one chose).

[servodude]

we had an electrician in yesterday first fitting the kitchen, He does a lot of Solar installs and car chargers.

he says garages and lofts are the norm for battery installs, and was blissfully unaware of the new Guidance/Code of Practice for battery location. He looked it up and was aghast - "so you can have a car with a massive battery on charge in your garage, or with 100l of fuel in it, but not a domestic battery?" which was pretty much my thoughts.

Paul

The phrase the guy in charge used began with an F and ended with stupid along with a few other choice words. I think his statement was along the lines of "You want it there, I want it there but the F stupid people who can cost me my job don't want it there".

Total insanity - and in some cases, I think people would not go ahead with an install. Congratulations government regulations (no idea whether the requirement was in existence before the Tories or from Labour or just a requirement to be part of the scheme initiated by the local mayor - either way it's a shambles when one can park a car with a bigger battery in the garage every day if one chose).

How's it worded? I love a bit of insanity for a laugh

[DrFfybes]

How's it worded? I love a bit of insanity for a laugh

Look for PAS 63100:2024

Paul

[Gerry557]

Rules is Rules.

My work often paid for removals but wouldn't pay to move garden sheds. Fortunately they would move the 7x5 dolls house.

I would be up to me to argue the random checker but this would be less likely if garden shed had been annotated with the wrong wording.

The good news is the sunshine out

[flyer61]

It is! 5.08Kw as I type. More than 10 times what we are using in the house.

Fitting finished Weds but there were two items missing. The extra battery and the Emergency Power Switch. Given I have yet to pay I will let them chase me up for the fitting of the missing items....

[the0ni0nking]

It is! 5.08Kw as I type. More than 10 times what we are using in the house.

Fitting finished Weds but there were two items missing. The extra battery and the Emergency Power Switch. Given I have yet to pay I will let them chase me up for the fitting of the missing items....

Just had a look at mine - have to do it via the panel on the inverter rather than on any app at the minute as it's still awaiting completion of registration but on an "ok" day its generating 1.1kW on the 8 panel side (West North West ish) and 1.4kW on the 7 panel side (East South East ish).

[DrFfybes]

Just had a look at mine - have to do it via the panel on the inverter rather than on any app at the minute as it's still awaiting completion of registration but on an "ok" day its generating 1.1kW on the 8 panel side (West North West ish) and 1.4kW on the 7 panel side (East South East ish).

That sounds low - I'm guessing not full sun yet where you are?

We very briefly hit the 6kW inverter limit just after 12:30 which is a first since about September, but today has been extremely variable.

Paul