Solar panels and battery - any real world reccomendations?

@BUDFORCE Surely you realise the savings are not that simple to work out, there are no guarantee's without a suitably large array to generate 8kwh over and above our usage during daylight hours every single day of the year. We have a 4kw array, and from 22 February 2021 to 21 February 2022 we generated 4113kw of electric, exported 2041kw, which means we used 2072kw, but that's not spread evenly, it depends on the weather, our usage, the time of year. Take last Tuesday, we generated 24.3kWh of electric between 7am and 19:45, so we could very easily charge that 8kw battery, the next day was just 10.72kWh, so we would have likely used the majority of that.

In December 2021 we generated just 71kWh for the entire month - we generate that in three good days this time of year. I only take meter readings every Monday so between 29 November 2021 to 3 January 2022 we exported just 7kwh, thats an average of 0.2kwh a day. In that same period we generated 77.47kWh, so we used 70.47kwh of the generated power.

@gpuerrilla Our house is L shaped, 8 panels face SW, and 8 panels SE on a 30 degree pitch (34 is optimum). If you can get all the panels on the south facing roof then that will generate the most power compared to a 50/50 split between the two roofs.
 
@Ron-ski

Thanks mate, that was exactly the kind of information I was after, very useful.

Indeed I am well aware that my little formula earlier was absolutely best case scenario, seems reality is far from though.

I guess really the only way to work out if and how much battery storage will save you is through your own statistics over a year, as each setup will differ.
 
That's my thinking, I know my current 4kw system won't provide enough power to charge an 8kwh battery, so we need more solar if we want a decent battery, but even with more solar there are barriers which further complicate it. If the battery can only charge at 3kw, and your generating 8kw, but the house is using 1kw, then thats 4kw that's going to get exported.
 
@Ron-ski thanks, just want an opinion from someone with panels too. From the app I seen today looking at install within the area the split setup as you describe nets about an hour-ish extra early in the day and later in the evening. The purely south facing roof generates better peak power overall when compared, so is it much of a muchness getting a better spread?

I have L shape house too.
 
There's not a lot in it, but all south facing will over time generate more. The ones on the left face SE, on the right face SW (closer to south than the other set), the top two (1.0.9 & 1.0.10) are partially shaded by a boiler flue. This is the total per panel since installation.

Totals-Layout.jpg
 
Im not really in it for the export, the 5p wont benefit much it was the two different quotes had completely different solutions. I can see the benefits of either setup.

Second quote has benefit of adding a battery down the line but mainly as it includes the optimisers. The app he showed me like yours of installs had west facing panels just over half the wattage compared to the south facing. Both installs are 5.5KW due to the DNO export limitation.
 
We don't work from home, washing machine has a timer, dish washer doesn't, but washing needs to be dealt with before we go to work, so not really practical to time shift them except at weekends.

@gpuerrilla its not about exporting, think about winter when there's not much sun, you then need as much as possible.
 
@Ron-ski

Ok thanks mate.

Good information, feel confident we are doing the right thing now not getting a battery off the bat, with the possibility to install one at a later date.

Similar to you I guess, we are getting a 4.5kw system, the roof is about 140 degrees, so just south of South east (if that makes sense) so not bad but not prefect either, I reckon our generation will be similar but both the Mrs and I work from home so will use more during the day anyway, then can put the dishwasher, washing machine etc on during the day.

Once we get statistics for a year we can make an informed decision.
 
I found this handy table, details the impact of not being purely south facing nor with the perfect 30-40 degrees angle

I worked out my roof is probably 56.31 degrees (18/12 ratio) (via some brick counting and some simple triangle maths which seems a standard so assuming im right) and it faces E and W pretty much

So for me I am probably around 68% efficiency compared to the perfect UK alignment, 20% loss for East/West facing and 10% loss for high roof angle

blog.spiritenergy.co.uk

Best Angle for Solar Panels in the UK and Beyond

Which is the best angle for solar panels? Compare the performance of solar panel tilt and orientation on roofs in the UK & around the world.
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Interesting though how a lower angle is better as you get further away from direct south facing. Makes sense, as the sun is lower the angle being lower matches better, so a very low angle east/west facing is as good as south facing (low angle), but optimum remains the often quoted 30-40 degrees south facing
 
gpuerrilla said:
So if you were placing panels @Mercenary Keyboard Warrior would you go all on south or spread them?
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From what I can tell, (I am just getting up to speed) partly it depends on your usage pattern and if your going batteries

Again don't take this as gospel, just my understanding so far :

If you have east facing panels they will generate earlier in the day, but drop of earlier in the afternoon, opposite for west facing.

So if you spread east and west facing in theory you should generate a flatter amount over the day, but you will generate less than if its south facing.

Batteries changes the dynamic a bit since once you have generation of enough to power your needs you will start topping that up, so for example if you have pure south facing your probably still going to be using stored energy early morning.

South facing will give more energy for the same panels, you cant get away from that. If you can reasonably store a high percentage of that then South facing is likely to be better in generation and hence payback terms.

I suppose also the angle should be considered, since if you have a low roof the difference is negligible between the facing, around 84% from 90-270 degrees.
This is why from what I read solar farms tend to be low angle and faced East West so they get a longer spread of less peaked output, reduced shading between panels (so you can fit them closer).
 
Yes good summation. The install I would get wont include a battery as the guy said the one to get would be 7 grand as ones cheaper/smaller just dont do job as well. It would be battery ready with the second quote so I could add one where this would allow time to see if its worth investment and allow for the technology/price/capacity to improve.

I currently work from home and would use most energy with white goods where possible so I guess a south facing occupies the brunt of core use time. I was just mulling over the west facing array as dependant on your stance this roof would benefit from say 3pm till sunset. I never thought much about E/W roofs until I looked into it.
 
gpuerrilla said:
Yes good summation. The install I would get wont include a battery as the guy said the one to get would be 7 grand as ones cheaper/smaller just dont do job as well. It would be battery ready with the second quote so I could add one where this would allow time to see if its worth investment and allow for the technology/price/capacity to improve.

I currently work from home and would use most energy with white goods where possible so I guess a south facing occupies the brunt of core use time. I was just mulling over the west facing array as dependant on your stance this roof would benefit from say 3pm till sunset. I never thought much about E/W roofs until I looked into it.
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Thats an expensive battery, although there are install costs as well. I saw somewhere it mentioned a Tesla battery install was typically a day for two people, so probably best part of a grand in reality.

Im sure he wont mind but @HungryHippos is in effect paying about £4k for his 8.2KWH battery on his install.

How much battery you need really depends on your usage pattern. There like everything else with solar is probably not a perfect solution since you can affect change to get most benefit from many scenarios. Such as you mention, use the white goods on sunny days close to peak generation as much as possible.

I think thats why understanding your usage, totals and patterns is important so you can see if having 4kwh, 8kwh, 13kwh etc battery is likely to be optimum for you.
You have to also consider winter months and that the benefit of batteries then is being able to charge from a dual pricing tariff. Charge overnight when its cheap and use during the day when its expensive.
These tariffs are by no means set in stone, they could be far more widely available and far more beneficial, or could dry up as more and more people switch to being able to take advantage.
The Tesla tariff on Octopus for example is superb, but its only with them, if they withdraw it for some reason then your expensive Tesla battery has far less benefit than right now.

From what I can tell, adding a battery mainly means you can benefit from your generation with less impact, so you can generate plenty, store plenty and maybe do your washing later afternoon, where as with pure solar you need to be far more open to moving things to sunny days and peak generation times.
 
You wont be making much from exporting, the old FIT was the way for that. I think this is what the installer meant when he said a decent battery to store maximum energy for that window of time means your going for a meaty quality one. His experience was indicating the cheaper ones just took longer to payback or werent up to the job was the impression I got. He wasnt trying to sell the battery in honesty but hinted the setup would allow it easily later on. It also looks like a cheap off-peak tariff is not on the cards - at least over here to charge any battery off the mains on the cheap.

We also have the capped export of 3.6 or whatever the figure is as the supply cable and transformer are for domestic so these installers are only offering systems that limit your wastage, give a shorter investment return time I guess.
 
gpuerrilla said:
You wont be making much from exporting, the old FIT was the way for that. I think this is what the installer meant when he said a decent battery to store maximum energy for that window of time means your going for a meaty quality one. His experience was indicating the cheaper ones just took longer to payback or werent up to the job was the impression I got. He wasnt trying to sell the battery in honesty but hinted the setup would allow it easily later on. It also looks like a cheap off-peak tariff is not on the cards - at least over here to charge any battery off the mains on the cheap.

We also have the capped export of 3.6 or whatever the figure is as the supply cable and transformer are for domestic so these installers are only offering systems that limit your wastage, give a shorter investment return time I guess.
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The smaller batteries often have lower output as well, so less able to power you through say an evening of the cooker on, TV on, dishwasher on etc
Really if batteries make sense the size is kind of irrelevant as long as you can use and charge it.
The important part is the cost per KWH of storage. It tends to have a sweet spot with higher capacities so hes kind of right, but its not that simple.
If you know you can add and use all the capacity from the battery, then assuming 6 months per year usage (assume excess power April - Aug) and a declining amount from 100% to say 80% over its life, say 10 years, then you can calculate at current rates the number of units you can save and see if that is higher or lower than the cost of the battery (and install)
You need to check the usable capacity (not all are 100%) and the warranty in regards degradation as they all vary.

Yeah right now about the best you can get on exporting is 5p unless you happen to already be with a couple of suppliers.
Whilst you don't technically have to use the same supplier to take your excess as you import from, the ones who offer a decent rate require that, and good luck being able to switch to them on the standard rates.

It sounds like with no off peak tariffs and a maximum generation of the lower limits its probably true that right now, especially as someone who can use it when its being generated, you wouldn't gain much from a battery.
 
Mercenary Keyboard Warrior said:
It sounds like with no off peak tariffs and a maximum generation of the lower limits its probably true that right now, especially as someone who can use it when its being generated, you wouldn't gain much from a battery.
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Yes I am just going by what I am hearing and although I would love to believe in the battery, due to their cost and/or lead time in some brands you would get them if money is no object and see if it works out later. If you have not got a few grand to dump on them right now, the traditional use what you generate should even with moderate household use will reduce the bills somewhat. With the suppliers only hiking the unit rate and standing charge up in the short term, it could be seen as simple damage limitation and let the six/seven years recoup most of the cost and hope the UK sorts out its power issues.
 
The old FITS system doesn't make any difference with regard to what you export, unless there was a proper export meter fitted. If you don't have a proper export meter then they assume we export half of what we generate, so if I export nothing I still get paid as if I export half, in the early years we used to export about 70%, now it's about half. Our smart meter record's the export but it's not acceptable for export reading's.
 
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