Solar Panels UK - is it worth it?

[nufan]

Inverter threshold.
Does anyone know whether smaller inverters are more efficient at low solar levels than larger ones.
My 5kWh SolarEdge inverter failed a few weeks ago & my installer has fitted a 3.68kWh inverter temporary to keep me going since there is a unbelievably long wait for a 5k model.
The reason I ask is, yesterday was my first day working again & the energy generated was considerably higher than I would expect for the amount of solar, when compared to high solar days in July with the old inverter.
Today is similar in that it’s now totally clouded over & I'm generating 20% of the system max.
Or am I imaging it’s better since I’ve gone five weeks without a working system.

Interesting- how big was the day one percentage difference? Could it just have been the older inverter being on its last legs?

I was interested as I’m prevaricating between inverter sizes + roof shading in autumn/spring here. If supply wasn’t an issue I’d go GivEnergy - but from what I understand their 3.6/5.0 inverters are the same hardware with a SW flag set differently - and this might explain “MPPT range” starting at 150v for both (I’m guessing MPPT range is the right attribute.

SolarEdge seems harder to pin down with the effects of optimisers. Found this in a review: “Since SolarEdge residential inverters operate at 350V DC (380V for the HD wave)”….in the context of min string sizes and optimisers needing 60v to 85v each.

Did they swap a non-SE inverter in? What make/model?

And general question to all - are there some inverters with lower thresholds to go for if you have shading? (I’ve been quoted Tigo optimisers, but still, I’d like to not make a mistake on the inverter)

 

[Yachtsman]

Interesting- how big was the day one percentage difference? Could it just have been the older inverter being on its last legs?

I was interested as I’m prevaricating between inverter sizes + roof shading in autumn/spring here. If supply wasn’t an issue I’d go GivEnergy - but from what I understand their 3.6/5.0 inverters are the same hardware with a SW flag set differently - and this might explain “MPPT range” starting at 150v for both (I’m guessing MPPT range is the right attribute.

SolarEdge seems harder to pin down with the effects of optimisers. Found this in a review: “Since SolarEdge residential inverters operate at 350V DC (380V for the HD wave)”….in the context of min string sizes and optimisers needing 60v to 85v each.

Did they swap a non-SE inverter in? What make/model?

And general question to all - are there some inverters with lower thresholds to go for if you have shading? (I’ve been quoted Tigo optimisers, but still, I’d like to not make a mistake on the inverter)

“Interesting- how big was the day one percentage difference? Could it just have been the older inverter being on its last legs?”

I hope not it was only 3 months old when it failed.

Temporary replaced with a SolarEdge 3.680 kW model until the warranty replacement arrives.

 

[Avendit]

I was interested as I’m prevaricating between inverter sizes + roof shading in autumn/spring here. If supply wasn’t an issue I’d go GivEnergy - but from what I understand their 3.6/5.0 inverters are the same hardware with a SW flag set differently - and this might explain “MPPT range” starting at 150v for both (I’m guessing MPPT range is the right attribute.

On my 8 vs 5kw comparison they both have the same startup voltage stated too, but I'm further into the 5's efficiency curve so you get more output at a given input. At least thats how I read it.

I think sizing is reasonably easy - aim for just below your installed kwh unless you have panels facing in different directions. If you have multiple angles, or just want more detail, run the simulations on PVwatts and add them together to get your max expected output. My 5kw is potentially still oversized as this method suggests the largest output I'll ever get in an hour is 3.4kwh. I do see transients higher than of about 4kw instantaneous, but its pretty rare. However, the proper design software pointed out problems with the string loading and total capacity installed going this small - 5kw was the smallest supported and available. Life's little problems with 2 arrays pointing in opposite directions I guess.

This probably isn't a great way to work btw, but its useful to sense check your installer's suggestions.

 

[nufan]

Thanks Avendit - I’ve been through your old posts in the thread - sorry took a while to find them - see you’ve mentioned the effect of efficiency curves there.

I’d have 8 NE, 6 SE and 4 shadier ones to the SW - 18x400w (anyone heard of DMEGC BTW?).

Running a pvGIS based simulation (if that’s what it was called) against their year long dataset I get something like a 3.7kW max - which is near bang on the DNO-limit induced capacity bracket offered by many of the manufacturers - so I think I’d be a fool to go higher (even if initially tempted).

What was the string-loading/total capacity thing?

 

[Avendit]

What was the string-loading/total capacity thing?

Using proper design software there is an upper and lower limit to voltages on a string, which are affected by temperatures and all kinds of stuff beyond my ken (I stick everything I know into this thread, but this is all just stuff found out through google and talking to my installer. Either source could be dodgy tbh).
According to my calcs I could have got away with a 4kw inverter, but on a 4 KW inverter I would have been over the max allowed panels (8NE, 11 SW). Now, it probably would have worked, especially as I'm up in Scotland and the panels will never hit their maxes, and nothing would blow up or set on fire, but with the installer's software flagging a problem I wouldn't have had a guarantee. So 5kw was the best combination of smallish and available they could offer and that is what we took. The 8k was just a delivery error that we installed to get the system up and running, and didn't loose too much from over June/July.

With an expected 3.7kw, installing a 3.6kw inverter seems pretty obvious, and means you don't have to talk to the DNO which may be a blessing.

 

[RedMod3]

Since there are a number of Powerwall owners on this thread, thought I would ask this here rather than start a new thread

Just had a Powerwall installed (at last) and trying to set up the Octopus Go in the Utility Rate Plan in the App.

Am I missing something or is there no way to set the Sell Price to 0.00? I don't get any money for export (yet), but the App doesn't seem to like 0.00 so have to set it to 0.01. Is that what everyone else is doing or is there some other way of doing that?

Also my Peak Rate is 13.8p, but the app will only allow 14p (£0.14), is that as near as I can get?

You've done right. I've set my peak to 16p, when it is 15.59p. I don't think it matters whether the rates are stop on or not.

 

[RedMod3]

Accepted my quote of £14,500 for 3rd Powerwall, 12 x 395W panels with optimisers, scaffolding, SE 3.68kW inverter (as panels west facing) and a SE export limiter. That gives us 10kW gross panels. Panels being fixed next week, PW and Inverter due October/November.

 

[ElectricPolice]

Accepted my quote of £14,500 for 3rd Powerwall, 12 x 395W panels with optimisers, scaffolding, SE 3.68kW inverter (as panels west facing) and a SE export limiter. That gives us 10kW gross panels. Panels being fixed next week, PW and Inverter due October/November.

Sounds smart, if not already a part of your quote get bird proofing done at the same time the scaffolding is up.

We've just forked out another £750 for scaffolding after 12 months to bird proof our panels after constant pigeon nesting and hearing them scratching around all day and night.

Whilst the scaffolding is up i've already washed the panels. Next I'm going to clean the roof, do some repair work on the ridge tiles, apply wet and forget for the moss, clean the gutters, facia etc.

Gotta make the most of the 4 weeks paid for

 

[Mrklaw]

Accepted my quote of £14,500 for 3rd Powerwall, 12 x 395W panels with optimisers, scaffolding, SE 3.68kW inverter (as panels west facing) and a SE export limiter. That gives us 10kW gross panels. Panels being fixed next week, PW and Inverter due October/November.

quote accept and PW available and installed in 6-8 weeks is fast! and that price seems very good

 

[ACarneiro]

And a Powerwall that quickly??

 

[Undecided_2]

I was told at least 12 months wait for a PW so I went with SolarEdge.

 

[RedMod3]

More facts, PW3 was ordered in April, but I decided to add 12 extra panels plus a new inverter, so they just wrote a new contract but I kept the PW price guarantee.

The installer is very busy, they are quoting July 2023 for new PW deliveries; they also can't get Solar Edge inverters until late October/November. The other issue is a shortage of resource to install anything. Demand is astronomical - I'm aware of two organisations going into solar and batteries in a big way.

I was lucky, a slot has come up next week to install the panels after another customer delayed their installation. The panels will not be connected for at least a month.

I really feel for people placing an order now, it could take months to get a full working system installed at the moment.

 

[RedMod3]

Sounds smart, if not already a part of your quote get bird proofing done at the same time the scaffolding is up.

We've just forked out another £750 for scaffolding after 12 months to bird proof our panels after constant pigeon nesting and hearing them scratching around all day and night.

Whilst the scaffolding is up i've already washed the panels. Next I'm going to clean the roof, do some repair work on the ridge tiles, apply wet and forget for the moss, clean the gutters, facia etc.

Gotta make the most of the 4 weeks paid for

Thanks for comments, but we already have panels, and no bird problem. Being in a bungalow, I'll prod them with a stick if they get annoying.

 

[Avendit]

Thanks for comments, but we already have panels, and no bird problem. Being in a bungalow, I'll prod them with a stick if they get annoying.

Sort of relevent:

 

[D4NS]

Didn't want to start a new thread.

Anyone got any recommendations on where to start with estimating what solar panels / battery / set up to look for to maximise solar?

I believe I can get 4 panels on the front (west) of property and 8 on rear (east).

What app / equipment is need to ensure I make the most of octopus intelligent over night as worst case?

Presumably there is a balancing act in having the solar battery discharged in time to start charging the following day or is it just a keep of keeping an eye on it and putting washing machine etc when batteries looking nearly full.

 

[RedMod3]

Didn't want to start a new thread.

Anyone got any recommendations on where to start with estimating what solar panels / battery / set up to look for to maximise solar?

I believe I can get 4 panels on the front (west) of property and 8 on rear (east).

What app / equipment is need to ensure I make the most of octopus intelligent over night as worst case?

Presumably there is a balancing act in having the solar battery discharged in time to start charging the following day or is it just a keep of keeping an eye on it and putting washing machine etc when batteries looking nearly full.

Look at your daily hourly consumption and look at the solar output by month; then add to the spreadsheet the effect of battery storage. Each person's situation will be very different, so you'll need to do it for your lifestyle.

The key is to balance usage, storage and solar.

 

[D4NS]

Look at your daily hourly consumption and look at the solar output by month; then add to the spreadsheet the effect of battery storage. Each person's situation will be very different, so you'll need to do it for your lifestyle.

The key is to balance usage, storage and solar.

Good advice, thank you. Awaiting first IO bill so that should help.

Is there any specialist equipment or decent apps that helps with the planning of whether to charge batteries from the grid over night?

I'm guessing keeping an eye on weather forecasts etc helps a lot. Ie I want to run from solar as much as possible and a full battery at 9am is pointless, as would be an empty one at 11.30pm.

 

[RedMod3]

Good advice, thank you. Awaiting first IO bill so that should help.

Is there any specialist equipment or decent apps that helps with the planning of whether to charge batteries from the grid over night?

I'm guessing keeping an eye on weather forecasts etc helps a lot. Ie I want to run from solar as much as possible and a full battery at 9am is pointless, as would be an empty one at 11.30pm.

The Tesla app is great. No peak power today for us. Can’t comment on other battery apps.

 

[Bigbadben]

Good advice, thank you. Awaiting first IO bill so that should help.

Is there any specialist equipment or decent apps that helps with the planning of whether to charge batteries from the grid over night?

I'm guessing keeping an eye on weather forecasts etc helps a lot. Ie I want to run from solar as much as possible and a full battery at 9am is pointless, as would be an empty one at 11.30pm.

Solcast provide tools to predict solar yield over the next 3 day. I use this to plan whether to top up on IO the night before.

The forecasts are generally more on the pessimistic side.

 

[Mrklaw]

Solcast provide tools to predict solar yield over the next 3 day. I use this to plan whether to top up on IO the night before.

The forecasts are generally more on the pessimistic side.
View attachment 856856

is this something givenergy provide you access to or is it manually setup?

I tried the solcast website which lets you set up a free home account on the web