Where do I start with solar panels and a battery install?

Newbie_John

https://forums.moneysavingexpert.com/discussion/comment/82112827#Comment_82112827

It does, but not significantly - up to 2p difference. Last neagtive prices were on 5 & 8th August.

Ive just checked random regions in UK on www.agileprices.co.uk and this month there were 11 days without prices below 20p (only 1 above CAP of 25p-ish) - so I wouldnt call it rarely - and August looks more expensive than any previous months.

Agile is all about average and for the last 6 monthsthe cheapest period 13-16 was 14.3p Mo-Fri 8.9p on weekends.

So currently if they dont need to charge daily - this could outperform any other EV tarrifs.

But aiming for solar and battery changes the approach - solar provides that "free" energy and tarrif with chepaest possible slot - provides the most expensive - so locking into any fixed tarriff thats under 10p should be the goal here as it provides predictability.

Regarding the topic:

• solar panels, get as many as you can - they cost little compared to installation costs etc.
• battery, I would aim at the size that covers 2/3 of your daily consumption during winter days - having IOG you can use that time to charge car, run dishwahser etc during cheap period and the battery should cover the rest of the day of things that cant be shifted

dharm999

https://forums.moneysavingexpert.com/discussion/comment/82112858#Comment_82112858

You’re right, I’d assumed freestanding on the flat roof would mean installed at an angle, not completely flat.

I’ve had a good look at the roofs and I think the east facing one could get 7, maybe 8 panels on it, the south one at least 4. The flat roof could get 10 on it I think, split south and west, probably 4 south and 6 west. That would give me 21, maybe 22 panels, so plenty of capacity. That would more than cover existing need, plus growing room for a switch to a heat pump when that happens.

QrizB

You’re right, I’d assumed freestanding on the flat roof would mean installed at an angle, not completely flat.

Flat roofs are a trade off. If you lay panels completely flat they never see full sun but they are also never shaded. If you incline them at the "optimal" angle (5-10 degrees less than your latitude) they shade one another for half the time (and pretty much the whole winter). Most flat-roof mounting systems (eg. Console tubs) incline the panels at 15-20 degrees which is a reasonable compromise.

Screwdriva

I would recommend a Van Der Valk ballast based flat roof mounting system - I estimate 12 X 515W Bifacial panels will fit on your flat roof, mounted at a 15 degree angle. Edit: See below for an image of these panels and the mounting system on a flat roof.

A survey will be needed to determine the exact number that will fit on the East/ South sloping roofs but I would guess between 10-12 should fit.

Paired to a Tesla PW3 today, this will be a very capable 11+ KWp system that should cost no more than ~£13K South of the border. (can't estimate Scottish pricing sadly).When the time for a heat pump comes, you could always consider an expansion pack to store more cheap energy for use when needed.

As others have shared, an EV tariff does pair well with Solar for 6 months of the year. Let's hope Intelligent Flux returns by Q2 2027.

I recommend this calculator as it has an easier user interface and is remarkably accurate as it uses PGVIS data.

Heedtheadvice

You some great responses from our well known posters. Plus you seem to be off to a great start!

I am S Scotland and I expect Edin to be similar to me for generation, you will have more clearer days.

For my low angle (22.5deg) due South I have experienced the predictable gen of 3800kWh from 4 kWp panels. Nearly as much as I consume ( house+EV+greenhouse) but still purchase a little. Overall cost nil.

I agree, maximise panels. Most summer days not really an issue for self consumption but on the poorer days and late winter/ autumn together maximising them out pays benefits.

Take note that you cannot fit panels right up to roof edges owing to wind effects on them and that is especially important in exposed areas, so make allowance for that - as should any installer.

At your power levels you will need an inverter capable of something in the order of 5kW to cope with the few peaks of demand or even higher if you manage high power generation so as to export excess and charge batteries and consume when possible. DNO G99 clearance ( prior application to DNO with design details is required by installer so should be in any quote).

I think screwdrivers panel recommendations would be worthwhile. Not so sure about Tesla as they have not been a recommendation by him in Scotland - installer limitation from memory.

My personal opinion on batteries is to go big and Fogstar seem great and very cost effective with 16kWh for around £2K and that can be readily doubled up. Your garage location could be ideal for inverter ( hybrid) and batteries and unless the garage is heated have the batteries with built in heaters for cold weather periods. Beware of battery mass!

Installer recommends are sparse for your area. Are you happy with your charger installers and do they do renewable?

Last a note of caution: one person I know who had a national organisation quote and they subbed to a central belt installer. Cowboys sprang to mind and the system had two serious issues within a year with no support!

NedS

@Heedtheadvice wrote:

I think screwdrivers panel recommendations would be worthwhile. Not so sure about Tesla as they have not been a recommendation by him in Scotland - installer limitation from memory.

Tesla's website show installers covering Edinburgh (this is how I found my local installer [not in Scotland]):

https://www.tesla.com/en_GB/support/certified-installers

Screwdriva

My advice is to focus your search on the PW3 purely because of the unmatched cold weather performance, 11KWh export capability (handy if you get a matching G99 export allowance) and IP67 rating.

I have known installers who travel to Edinburgh from South of the border, making prices most competitive in that part of Scotland. That said, I would be surprised if you managed to get a quote under £14K all inclusive.

dharm999

Thanks to everyone who has replied, some very helpful advice. Next step is to get some quotes from local installers, and see what they recommend. I will be back when I have that