Hi, Joining for some advice.

[johnb2713]

If you install panels and batteries etc at one time it is VAT exempt. Installing the batteries later you pay VAT.

This is changing in February 24 and batteries can be purchased later with VAT at 0%

https://www.gov.uk/government/consu...carbon-emissions/outcome/summary-of-responses

 

[Ollie78]

I personally would turn it around the other way, look at your daily consumption figures and get enough battery storage to cover that plus a backup margin. Look at your peak consumption and use that to size the inverter. That creates a battery system that can run the house all day at off peak pricing. Now with the budget remaining get as much solar that the budget allows. There are times with companys like Octopus where they have 'saving sessions'. If you export to the grid during these times you get paid up to £4 per kWh (this years price), a considerable amount of money can be made if you have the capacity to store energy and discharge it into the grid at the appropriate time. On my system I bought energy at 7.5p kWh and sold between £2.25 and £4 giving me an income in December of £135. These grid balancing sessions are definitely on the increase and worth taking into consideration. During the good weather I export all what my solar generates with my house running on battery, again buying energy at 7.5p but selling my solar at 15p, not a lot but it does add up.

If I look at it this way then I think the 11kwh batteries are possibly about right. Our usage is less thn 9kwh per day based on the 3100kwh per year.
However, in order to take advantage of the various Octopus schemes we would need to make sure it can force discharge at the very least. The Givenergy ones are the only official partner for intelligent.

Hi Ollie, suggest you take a look at the generation you'll get from the S.E.W. PV system.

You can get an idea of generation potential for your location with PVGIS or easy-PV and see how little you'll get p.a. or p.c.m. to help you see if it gives a worthwhile dent in your electricity consumption.

PVGIS will just tell you generation, pcm, and depending on the years selected in the 'monthly data' tab will give a +/- yearly spread

easyPV has an in-built usage profile too which varies with time of day and time of year so also gives an indication of how much self-consumption you'll get. It will do a shading factor calculation too. You'll need you annual usage as an input.

With only four panels per roof then an inverter with a low startup voltage would be preferable, e.g. Fox ? However not many have 3xMPPT trackers, i.e. one for each roof and it's not a good idea to mix directions on one string. So microinverters by Enphase or SolarEdge seems sensible.

Rough sums, retail, not trade, prices, for 12 panels
Enphase IQ8 about £150ea, envoy ~£380 = £2180
Solaredge S500 ~£60ea + 5kW Solaredge inverter ~£1050 = £1770 (5kw from 12*420W and the 6kW version is an extra £300)

I might be missing something but Solaredge looks similar price to Enphase solution ?

Edit: playing in easyPV with longi HiMo6 425W panels indicates an upper limit of 11 panels per 'branch' for Enphase, depends on the model, some are max 10 per branch. Assuming 4000kWh p.a. usage the yield is 30-35% of usage, without a battery. Solaredge should take 12 panels. Depends if you real limitation is roof space or Enphase.

I will have a proper look at the PVGIS ( had a quick look before but was a bit baffled ) and easy PV as well.

The annual generation figures from the various quotes have been:
Quote A 4290 kwh (enphase iq7+, 420w panels ).
Quote B 4349 kwh ( tigos and solax, 410w panels)
Quote C 4663 kwh (enphase 1q8s 425w panels). We have virtually no shading.

Your comment about the 3 sides and not many 3 mppt inverters matches what I have been told elswhere and why we were leaning towards the enphase.
It is interesting that your sums come out with the enphase and solar edge being so close, the provider of quotes b and c said that the solar edge option came out even more expensive than quote C when he looked at it.

The final part where you say there is a maximum of 11 panels is very interesting indeed as both companies initially suggested 11 panels. Until I said that someone else had suggested they could fit 12 on a previous quote. I am now wondering if this is why, not a space constraint but a "branch" constraint maybe.

I must say that I really appreciate your time looking into it for me.

all panels are rated by STC, standard test conditions, it's worth having a look at the Californian state tesing of panels or PTC, which is suppossed to be more 'real world' and usually knokcs 10-20 Watts off a panel , howver 290w on a 420 w panel, that's roughly 30% - drivel! Even my 12 year old panels still hit within a few watts of their peak output from installation on a regaular basis. They might be nearer the mark if you are based in the Shetland Isles....

lots of manufacturers have 'training courses' which are free and mostly sales and marketing.

Tigos are enhanced bypass diodes, which all panels have, a completely different kettle of fish to solar edge and microinverters.

John is also correct, batteries offer greater financial savings than the solar panels do. Now I'm a bit biased in that I like solar for green credentials, but financially it's expensive to fit compared to batteries alone, plus risks potential roof issues if the fitters are 'not so clever'.

Interesting what you say about the undersizing of the enphase 1q7. it does make me wonder why they are sized as they are when most panels now are well over 400w.

I had heard this about the tigos and that they were not really very useful for shading because the panels have bypass diodes anyway, but in our case they were basically specifying them to create one string into the inverter instead of 3.

The plot thickens, I will go and have a play with the pvgis and easy pv.

Thanks

Ollie

 

[binky]

I had heard this about the tigos and that they were not really very useful for shading because the panels have bypass diodes anyway, but in our case they were basically specifying them to create one string into the inverter instead of 3.

If they are trying to use tigos to put all the panels on a single string, that's a bad idea. The MPPT will be trying to find the optimum power point for 3 sets of panels operating at different levels. Google how mppts work.

Solar edge is a great system, but always was expensive, hence Enphase is popular.

 

[Ollie78]

If they are trying to use tigos to put all the panels on a single string, that's a bad idea. The MPPT will be trying to find the optimum power point for 3 sets of panels operating at different levels. Google how mppts work.

Solar edge is a great system, but always was expensive, hence Enphase is popular.

This is the diagram of what they were going to do with the tigos

Do you think in this case I should be discounting this method and either going enphase or solar edge. Or is there another way to deal with the awkward 3 roof arrangement?

Ollie

 

[binky]

That arrangement will mean the arrays will effectively be fighting each other. It will work, but never at an optimum output. I would avoid that!

 

[Ollie78]

That arrangement will mean the arrays will effectively be fighting each other. It will work, but never at an optimum output. I would avoid that!

This is crazy to me, two companies have suggested this exact method with tigos. I think they just see multiple arrays, don`t have a 3 input inverter and so just whack on some tigos. I wonder how many systems are installed like this all over the place.

Update on the Alpha ess batteries I have had an email from the company, they say the following.

"The Alpha battery will not directly export to the grid.
You can export from the PV however Alpha intentionally do not let the battery export to the grid."

"This is because idea of having a battery is so that you store any unused energy throughout the day for use in the evenings however, if you exported from your battery then you would be reducing your coverage and self-sufficiency in the evenings. You still have the ability to export any excess generation to the grid once the battery is full however it’s just the battery that doesn’t have that functionality."

"The Alpha batteries are also compatible with all Octopus tariffs for off-peak charging, it’s just the export that’s purposefully restricted. As I say, you will still have the option to export any excess directly from the PV, it’s just the battery they don’t want to drain."

Then most tellingly they say this.
"Although Alpha’s decision not to let the battery export is a protective measure, due to demand, they will be bringing out the exporting functionality around Q3 2024. This will be a software update as opposed to needing to replace the whole unit."

Which surely shows that there must be a realisation that people want to have more control over their batteries.

My question here is what are they "protecting" or "purposefully restricting" currently that will be suddenly unprotected or unrestricted when they update the software later in the year?

Ollie

 

[binky]

Some companies seem to think This are the answer to everything. I might be wrong, but I'm pretty sure I'm not .

Demand dor exporting has become more popular as a way of paying for batteries. Sounds like Alpha are a little behind the curve.

 

[Kot]

I am very happy with my SolarEdge Inverter and 10kwh battery it is great for shading issues and avoids fighting lol but of course it’s not as cheap as Tigo’s but horses for courses — worth researching

 

[Ollie78]

I am very happy with my SolarEdge Inverter and 10kwh battery it is great for shading issues and avoids fighting lol but of course it’s not as cheap as Tigo’s but horses for courses — worth researching

Initially I was not looking at specific brands or systems until I noticed all the quotes we had were so different, then I started to look into it all and found it to be a pretty complex market. So now I am trying to find the best quality and value.
I will certainly look into the solar edge stuff. I definitely think the Tigos are not the way forward.

Ollie

 

[Ollie78]

I have been playing around about with Easy PV, open solar and PVGIS. I got similar yearly generation figures from the first two at around 4200kwh with 420w panels, but the PVGIS was a a little more pessmistic / realistic at 3608kwh. Though I may have entered a perameter wrong in there somewhere.
It is some confirmation that the quotes I have received were not super overestimated in this area.

Interestingly the system I did with solar edge stuff had a very similar yearly generation figure as Quote A ( with the enphase IQ7+ ) which is odd because of the 30% undersizing of the micro inverters as pointed out by @binky .
Does this mean that the claim is true about the earlier startup etc ? so over a year the clipping is cancelled out by more generation in low light situations.

I also have a question about the pricing generated by Easy Pv and Opensolar, the price of the solar edge system I did came out quite similar to the initial enphase one. Which is about what @bladerunnerpv was suggesting.
I left the "markup" on 25% as I was not sure what principle the system worked on. I am assuming this is an indicator of the installed cost as the programme generates a customer quotation. Is 25% a good guess or should it be more.

I did try and go on the official solar edge designer to make sure I was entering the right components but because I am not a vat registered company It won`t let me do it, which is a shame because it looks really good.

I am not necessarily intending to do any of this myself but I find it interesting to find out how it all works and compare things.

Is there any other recommended software I can use as a non trade person?

Ollie

 

[binky]

Free versions of software are unlikely to be that accurate, especially when it comes to optimisers and the like