Guidance for solar system please

Screwdriva

Solarchaser said:

After that, people's own experiences colour their advice.
For instance, Screwdriva does alot of helping people with solar quotes, and pushes historically for certain makes of panel and solaredge inverters as he has had good experiences,  or his research supports it, more recently he has pushed for Tesla, as his research supports it.
He also always pushes for 10 year warranties, all very honourable and should be applauded!

I've never used solaredge, and the friends that I have who got a system with solaredge, didn't need it, and essentially paid extra for something that wasn't required as they had no shading issues.
There is an argument about individual panels failing, but that is so very rare as to make the point moot.

I view what I do as helping others maximize their chances of a positive PV experience by ensuring the best quality of component brands for less money than any other quote, from installers who have consistently good feedback. 

I recommend SolarEdge as I have real world examples of their aftersales support on 2 inverter failures (out of 120+ installations I've helped with). Like you, I do not recommend Growatt as I find their aftersales to be terrible. If a brand delivers performance and strong after sales support at a competitive price, I'll recommend it. (Sadly this is getting harder to find with each year that passes)

I was never impressed by earlier generations of Tesla vehicles but have always been impressed by the PW2 and am blown away by the PW3. I have also recommended other brands of battery inverters in the past (GivEnergy's All in One being the closest contender) but frankly, none of them come close anymore.

I suppose it must appear that I am "pushing" a couple brands but what I try to do is to help end users avoid unpleasant experiences with PV technology down the road, while saving them as much £ as possible. It's the only way we will get from <10% Solar penetration today to where it needs to be! 

Solarchaser

Bad choice of words on my part, recommend would probably have been a better word than push, it wasn't supposed to look like a negative thing.

I believe you are doing this for the betterment of people's solar returns and experience,  just to be totally crystal clear.
As I said already, I think it's all very honourable and should be applauded. 

I have a different view to you on some things because of the fact I've been a service engineer in many industries and so seen inside various types of machines and gizmo's that various big name companies make and while you are of the view (as you have said it a few times)
 "you get what you pay for"
I know for certain, that's not the case.

There are certain manufacturers who do the best they can, get the best components on the best quality PCBs etc, but most dont, or maybe they did 20 years ago, and then someone came in and told them costs needed cut etc.

In fact we all see the flaw in "you get what you pay for", when we see the various quotes for solar panels etc, but with a high final price, because really what you are paying for is someone's profit.

Not all the time, not in every industry etc, but it holds true well over 75% of the time.
Think of the brand new £50k car that's £40k a month later, and the company is probably still making £10k profit on the sale.

I'm of the view if you can get what you need for £5k cheaper, then you should do that, especially when you are working on ROI calculations to justify purchases.
Different folks, different strokes.
Not a right and wrong, just different opinions 👍

ddi

I took the ‘push’ to mean recommend with evidence. Thank you!
Is it better to have PW3 with extension pack or 2x PW3 please? The array will be 25 x 500’s. So I’m guessing that will only achieve maximum 12.5kw per day? So only filling one PW3 if none used. But we could use the PW3 (either two of them or with an expander) to store overnight? Given we use circa 40kw per day year round what are your thoughts please?
Also do the pw3’s store energy for several days (when on holiday for example)?
huge thanks 

Martyn1981

Hi, there may be some confusion there.

An array of 25 500Wp panels would be around 12.5kWp in total, but that's the power not energy, that it can generate. In fact the energy will vary, depending on the level of sunlight and the temperature too. A 12.5kWp system will only generate about 10kW in strong sunlight once the panels have heated up.

But here's the good news, that's per hour, eg, if it's generating 10kW for a whole hour, you will generate 10kWh. On a really good day you might generate ~70kWh (60kWh to 80kWh perhaps), but of course on a dark cloudy day in December it may be zero. In the UK, a good system (well sited and mostly facing between SE and SW) will probably generate ~1,000kWh's per year, per kWp installed. So 12.5kWp may generate around 12,500kWh pa.

So your system could, on a good day, fill a PW3 (13.5kWh) in a little over an hour.

Storage for days, while you are on holiday, will depend entirely on what the baseload for the house is. If it's mainly fridge and freezer, and not much else, then you will be fine for days, even if there is no generation.

ddi

@Martyn1981 that’s fabulous news! It wasn’t making much sense before. 

Martyn1981

ddi said:

@Martyn1981 that’s fabulous news! It wasn’t making much sense before. 

No problem. A great tool for estimating PV generation is PVGIS but it can be a bit confusing, so I've 'stuck a pin' in Guildford, entered 12.5 in the kWp box, 35d in the roof pitch box, and -45d in the azimuth box, which translates as SE (45d before south (the sun)).

PVGIS guestimates are very fair, maybe a bit pessimistic in fact. But of course this is an average year, in reality you will get good and bad months, good and bad years, but should give you some confidence at 12,029kWh.

If you try it yourself, you'll be able to hover the mouse over the monthly charts for an actual figure. But the low is Dec at 320kWh and the high is July at 1,584kWh.

This is what I got:

ddi

That’s fascinating and very encouraging! Thank you. 

Screwdriva

ddi said:

Is it better to have PW3 with extension pack or 2x PW3 please? The array will be 25 x 500’s. So I’m guessing that will only achieve maximum 12.5kw per day? So only filling one PW3 if none used. But we could use the PW3 (either two of them or with an expander) to store overnight? Given we use circa 40kw per day year round what are your thoughts please?
huge thanks 

Personally, I would not design battery storage to compensate for hot tub/ pool use in the summer months, when the sun is shining bright and 12.5 kWp of Solar panels will offset most of that consumption. There's also the possibility for more efficient/ timed use of the pool.

But if you had a heat pump, as an example, I would definitely factor its peak draw + peak draw of all daily use appliances into my calculations (Heatpump + other appliances that may run at the same time). If the total is over 11 kW then I would go for dual PW3s which offer 23kW of continuous output vs. with a single PW3 + expansion packs which offers 11kW of continuous output. 

Hope this makes sense?

ddi

Thanks @Screwdriva we have an ashp for the pool but the house is heated with gas. But all cooking is electric. We’ve only had a meter since December and this summer will be first time with a pool & hot tub. Our previous usage has been anything from 35-55 kw per day but that’s from Dec to March. Our estimate is 14,000 per year. Before the pool addition! 

Annoyingly the ashp has been on for the pool 24/7 for the last week (I know I know) and daily usage was 120 kw per day for that week. This will NOT happen again. We have a gas option and can time the ashp for daytime only & only use the ashp when pool is up to temp & daytime only & only in summer season. Defo not 24/7.

My thoughts are that in summer, yes the solar will offset our usual usage (45-55) but we had no meter so no clue if similar to winter usage or not. To be honest I’m struggling to know where to start with calcs as the meter is so new. As us the pool. 

For winter I’m thinking we will generate only 10 kw per day so will purchase/import via octopus flux night rate to the PW3’s for use the following day esp peak times (4pm-7pm). 

Is that a reasonable plan? 

Screwdriva

ddi said:

Is that a reasonable plan? 

Any plans for a heat pump for the house? If not, I would stick to the single PW3 with expansion pack(s) to start with and save some £ now. You can always add another one later (I'd negotiate the installed price for another unit now at your option). 

Best of luck with the install - hope you share images of the result on here

P.S, A heat pump for a pool is a wise investment!