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Looking at putting in a PV system

Solar Photovoltaic (PV)

Last Post by Tim441 3 years ago

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digger42

(@digger42)

Active Member Member

Joined: 3 years ago

Posts: 4

Topic starter 21/12/2022 11:23 am

Hi , quick intro

I am an electro/ mech engineer (dirty hands)

Midlands uk based

Looking at a PV system next year so it’s a very steep learning curve for now .

Hoping to learn and help in any way I can

Regards Jeff

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Mars

(@editor)

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Joined: 5 years ago

Posts: 4241

21/12/2022 12:45 pm

Welcome to the forums Jeff. Good luck with your PV installation. Did you have any initial questions or do you have an idea of what you'll be proceeding with in terms of kit, brands and size of array?

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digger42

(@digger42)

Active Member Member

Joined: 3 years ago

Posts: 4

Topic starter 21/12/2022 5:29 pm

Thank you for the welcome .

Getting my head around all the components and options but …

If I get limited to G98 can I still max out on panels ?

Do I then have a big inverter with an export limiter ?

Assume 8kW panels - 2 usage , 3.6 export where does the rest go ?

if the panels are making energy I assume it has to go somewhere , battery full , export maxed, all appliances on - where does the excess go ?

Regards Jeff

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AllyFish

(@allyfish)

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Joined: 3 years ago

Posts: 518

21/12/2022 6:50 pm

Hi Jeff. Solar PV panels are now £0.50 per watt, electricity cost is only going in one direction, so max out all available roof space. Exporting power is a mugs game now, you get pennies for what you generate and your electricity provider sells that on as a massive profit. Someone else pays the price capped standard rate/kWh for what you micro generate and get paid 4p/kWh for! Don't give them the satisfaction. Use what you can, store what you can in batteries. If you have a system tank with an immersion heater, get a solar diverter like an I-boost. That will dump surplus electricity into your immersion - free hot water in summer, and very helpful even in winter. If you've maxed out on export and are generating more than you can use or store instantaneously, your system inverter will simply limit the solar PV output to 3.68kW to grid.

Batteries are not cheap, and the global demand for lithium batteries will keep prices high and handsome, but if you can't afford the initial capital outlay for battery storage, get a hybrid inverter that's battery ready and allow space for batteries. I had 3.6kW PV installed October, and planned to defer the 6.5kWh battery until Spring, but I think battery prices are going to rise next year quite significantly, so I'm getting a battery fitted early in the New Year. Won't really be of benefit to me until mid Spring however.

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Derek M

(@derek-m)

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Joined: 5 years ago

Posts: 4425

21/12/2022 7:12 pm

I think that at the moment if you have a battery system installed at the same time as solar PV, you can save the VAT on both.

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Toodles

(@toodles)

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15/01/2023 2:19 pm

Hello, I can confirm that having a battery ordered within the same contract as that for PV will allow the contractor to apply zero rate VAT to the battery system as well. Ordered on its’ own, the battery will have VAT applied to it and its’ installation cost. As to whether it is worth trying to export your surplus energy (and I stress ‘surplus’), this is indeed worthwhile with the right tariff. I am with Octopus Energy and have the Agile tariff and export using the Outgoing Agile; under this scheme, the amount paid per kW/hour will vary but I reckon my average unit rate has been in excess of 20pence. I received over £200 credit in the space of less than 2 months production last August and September. I hadn’t the means to store my excess energy then but now have a Tesla Powerwall; however though I turn on the immersion heater and try to ‘soak up’ my sunny weather excess with a convection heater, I still find that Octopus have credited me with a few pounds in a month. I have 8.1 kWp. of PV and am to have an ASHP in a few weeks and an Eddi diverter will be fitted at the same time. I am having a Sunamp Thermino ePV 210 (short of space for a large tank!) and this will be connected to the Eddi and by this means, my DHW will be catered for by PV power with grid backup if needed. Regards, Toodles

Toodles, heats his home with cold draughts and cooks food with magnets.

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Toodles

(@toodles)

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Joined: 3 years ago

Posts: 2576

15/01/2023 2:29 pm

Oh! And as a sort of post script: My MCS registered installer applied to my DNO with a G99 form - took the usual long period of time but was granted and I am now able to export up to 5kW. I know of others who have a 3 phase supply and can then have plural Powerwalls allowing for greater storage and export allowance. This is an expensive game mind you and probably not worth it if your sole aim would be to export more energy! Regards, Toodles

Toodles, heats his home with cold draughts and cooks food with magnets.

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Tim441

(@tim441)

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Joined: 3 years ago

Posts: 398

22/02/2023 11:23 am

Solar

Do as much solar as practical on south roofs ... and west & East is also well worth considering. Obviously shading needs to be considered.

If you go over 3.68kw panels... in reality around 4kw ...

- You need permission from grid (DNO)

- but installer can get that easily in most cases to go up to say 6kw... and maybe more. They can check.

Add batteries... probably more than you think! So if planning one... do 2! I have 3 x 8.2Kw

- it's vat free with original installation

- it's more backup for emergency

- as the power companies are doing more flexible pricing you can buy more at cheap rates... and sell back at peak rates

- as well as storing your own production from solar

- even though batteries can in theory be installed outside I think much better inside as they lose efficiency when it's very cold - just when you need them most. And need a bit of protection ideally from rain in any case.

Check the inverter sizes proposed. e.g. For max they can charge batteries, supply house normally from grid+ batteries, supply in emergency etc

EPS

If you have batteries you may as well use emergency functionality. Most installers cant be bothered to offer it

- also vat free as part of installation I think.

- depending on inverter there will be a maximum draw. Likely you can get 3.6kw ... or more. But huge draw is not much use unless you have enough batteries! And they're filled!

- depending on batteries (and how full) ... Will impact how long eps will last. With my 3 batteries if I was full ... and with sensible usage mine should last 24 hours... or more.

- some idea of methods.

Auto changeover is likely to be expensive - in our case simply impractical on cost and wiring grounds

Manual changeover is what we did & was very practical (might add £1000 to cost?)

Just adding a couple of sockets seems too basic & not best option.

We have Givenergy kit. Seems quite good... lot cheaper than Tesla. But Tesla is probably better.

While doing the wiring changes we added a couple of emergency lights so that we can find our way to changeover in powercut etc

Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV

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