Solar Panels UK - is it worth it?

[Dilly]

powerwalls behave fine in summer and winter. It’s November and now that are bit iffy.
Up to yesterday AI got it right but after a couple of very sunny days and wife charging her Outlander from the Powerwalls once on purpose and a second time by accident, we started the evening on 39%.
by the time 00:30 came we were probably down to 29%.
I set the reverse to 25% before going to bed. I got up for a pee at 01:30 and found not much going in but both cars charging on cheap rate.
I whacked the reserve up to 70% and woke this morning at 75% which was fine.
with solar not too bad today we reached 100% about 2pm and the immersion diverter cut in.
had I not been up, it might have been a disaster!
AI only looks back. Until forecasting is available (if ever!) a target value would be mighty useful.
i can look at the forecast and predict my needs with some accuracy after 2 years of experience.

 

[phil4]

So do you use the "backup reserve" as a way of setting a target? It sounds like it from what you've described above.

 

[Dilly]

So do you use the "backup reserve" as a way of setting a target? It sounds like it from what you've described above.

Whatever you set reserve to will be exceeded by some amount. In dull weather it will probably fill.
where a few dull days will follow a run of sunny days, I look at the level at bedtime and set the reserve just below wher the percentage will be at 00:30.
there is a good chance that one of us will be up in the night if we need to raise the level though to be fair we have enough capacity for it not to be a regular occurrence.
it is a bit hit and miss!

 

[Fred2]

What it actually needs is access to a forecast. But that probably requires £££ for a subscription.

For what it’s worth it feels like when paired with the octopus Tesla energy plan there is an element of that. The past few days of solar haven’t been huge (15 kWh, 12 kWh) relative to my daytime consumption & the PW was charging overnight for those. Last night the forecast for today was for a very sunny day & it hasn’t charged overnight at all. Obviously now the forecast is somewhat worse but it does feel like there might be something going on. It could also be more driven by wholesale prices (although those are also weather forecast linked I believe) - it will do things like charge in 2-3 blocks overnight rather than all in one go

Obviously on this plan you have no control whatsoever, so a bit irrelevant!

 

[scdoubleu]

Whatever you set reserve to will be exceeded by some amount. In dull weather it will probably fill.
where a few dull days will follow a run of sunny days, I look at the level at bedtime and set the reserve just below wher the percentage will be at 00:30.

Sneaky! I tried that last night. Raised backup reserve from 15% to 30% before bed. This morning, (using HomeAssistant) I could see the battery had drained down to 37% by 0:30am then charged up to 94% on off-peak angry pixies.

I expected less given yesterday was fairly sunny so, at least anecdotally with a sample size of one, this trick appears to work.

Today's laundry day, so despite the sunny forecast we're going to need a decent reserve in the Powerwall.

 

[Avendit]

Do the same rules for protecting the powerwall apply as the car battery? Ie generally charge 20-80%?

 

[Dilly]

Sneaky! I tried that last night. Raised backup reserve from 15% to 30% before bed. This morning, (using HomeAssistant) I could see the battery had drained down to 37% by 0:30am then charged up to 94% on off-peak angry pixies.

I expected less given yesterday was fairly sunny so, at least anecdotally with a sample size of one, this trick appears to work.

Today's laundry day, so despite the sunny forecast we're going to need a decent reserve in the Powerwall.

That’s good to hear.
Last night I went to bed at 10:45. PW’s had 84% so I left them alone. As expected woke up to 70% with nothing imported over night and a full bore sunny day in prospect. They’ll certainly fill today. Next few days may be tricky as there won’t be much sun until Wednesday. beyond Sunday they should behave correctly though.

 

[GlynG]

Is the Powerwall battery recommended 20% to 80% charge?
My Solax Triple power batteries are Depth of discharge 10% - and charge up to 99% (It never shows 100% on the display)
I don't import overnight electricity to charge my batteries- always just left it to the sun to do it but I don't have a cheap overnight tariff - so nothing to gain.

 

[Dilly]

Is the Powerwall battery recommended 20% to 80% charge?
My Solax Triple power batteries are Depth of discharge 10% - and charge up to 99% (It never shows 100% on the display)
I don't import overnight electricity to charge my batteries- always just left it to the sun to do it but I don't have a cheap overnight tariff - so nothing to gain.

There is no control to limit charge/discharge. It’s self controlling.

 

[PITA]

Here's how mine work...

Last night both Powerwalls were at about 20%. It's going to be Sunny today, so I want Powerwalls about half full.

Car was about 34%... but I want it at 95% for this morning. Too much needed within a 4 hour window on a 7kW charger.

We're on Octopus Go Tariff with a 4 hour Window of cheap electric at 5p

So at 00:30 both Powerwalls and Car start charging at full 15kW drawdown. After 4 hours the Powerwalls are at 100%... and stop charging.

But the Car isn't finished yet, so now the Car Charging flicks from Grid Power to Powerwalls, and start draining the cheap rate power from them instead.

So now the Car is at 95% on cheap rate, the Powerwalls start the day at 50%... with a good Solar Day ahead of us, while I'm out in the car.

As I've mentioned before, two Powerwalls can discharge at 10kW which is ideal for a 7kW car charger attached to them.

One of the reasons I'm switching to a second 3 Phase car charger, is so that I can charge two EV's and the Powerwalls overnight at the same time.

Or get 11kW charging speeds for more cheap rate power in the 4 hour window... but the secondary 3 phase charger isn't connected to the Powerwalls... it'll be Grid Only, as it'll be fast enough to charge by Grid on it's own.

 

[PITA]

Loads of people have condemned me for wanting a second EV Charger (especially a 3 phase version)... as being a complete waste of time.

They've argued (Specialist Installers) that a 7kW charger is more than enough for two EV's to share. Or even two 7kW chargers load balanced at 3.5kW each... WTF

I disagree...

Charging quickly, and at high capacity from home will be key for low cost EV motoring.

I've likened it to the internet. Everybody thought dialup was fast enough once.

No thanks, I'd rather have Fibre Broadband by comparison

I'm even considering upgrading in the future to a 50kW rapid DC Charger on 3 phase... but while we've still got cheap overnight tariffs that are 4 or 5 hours long, that won't be needed yet.

 

[dazzap]

Anyone got a givenergy battery system?

I was watching a YouTube video and it would appear to give you the option of choosing if/when to export power to make use of higher export rates which they said the powerwall doesnt do. I've got 3kW PV array w/o any kind of smart controls or storage and find it takes a lot of effort to try and only charge the car when the sun is out.

 

[dazzap]

Here's how mine work...

Last night both Powerwalls were at about 20%. It's going to be Sunny today, so I want Powerwalls about half full.

Car was about 34%... but I want it at 95% for this morning. Too much needed within a 4 hour window on a 7kW charger.

We're on Octopus Go Tariff with a 4 hour Window of cheap electric at 5p

So at 00:30 both Powerwalls and Car start charging at full 15kW drawdown. After 4 hours the Powerwalls are at 100%... and stop charging.

View attachment 767660

But the Car isn't finished yet, so now the Car Charging flicks from Grid Power to Powerwalls, and start draining the cheap rate power from them instead.

View attachment 767658

So now the Car is at 95% on cheap rate, the Powerwalls start the day at 50%... with a good Solar Day ahead of us, while I'm out in the car.

View attachment 767659

As I've mentioned before, two Powerwalls can discharge at 10kW which is ideal for a 7kW car charger attached to them.

One of the reasons I'm switching to a second 3 Phase car charger, is so that I can charge two EV's and the Powerwalls overnight at the same time.

Or get 11kW charging speeds for more cheap rate power in the 4 hour window... but the secondary 3 phase charger isn't connected to the Powerwalls... it'll be Grid Only, as it'll be fast enough to charge by Grid on it's own.

So with Octopus go you can import as many kWh as you want at 5p but just for the 4 hours a night?

 

[PITA]

So with Octopus go you can import as many kWh as you want at 5p but just for the 4 hours a night?

Correct, yes.

But your home Grid cable infrastructure has to be able to cope with it... if you want to go big.

We've upgraded and got Commercial Grade cabling at our house. The DNO guy laughed and said he's seen Stately Homes with less capability

In our case, the DNO upgraded our house cabling free of charge, so we got very lucky.

 

[browellm]

Anyone got a givenergy battery system?

Yes.

I was watching a YouTube video and it would appear to give you the option of choosing if/when to export power to make use of higher export rates which they said the powerwall doesnt do.

It is possible to do brokerage on and control your import/export. You'd need to have an appropriate outgoing tariff like Agile Outgoing, which will limit your import tariff options to either Agile Import or Economy 7.

If you are considering it, remember you'll need to factor in round trip losses through the inverter. The system isn't as efficient as some high-end systems like the PW, but that's the trade off for a much lower capex.

 

[Avendit]

anyone any idea of the brand of battery so.energy are using? pictured here: https://solar.so.energy/get-started, but I can't find any info about the manufacturer or what kind of app it comes with.

 

[init6]

anyone any idea of the brand of battery so.energy are using? pictured here: https://solar.so.energy/get-started, but I can't find any info about the manufacturer or what kind of app it comes with.

Looks like this battery:

Home - Puredrive Energy

puredrive-energy.co.uk

At least the 5kw one they quoted me for.

 

[init6]

And it looks like Puredrive app:

PureDrive

The PureDrive app enables owners of PureDrive batteries to monitor their homes’ energy on the go. With this app you can: Check how much charge your battery has and how it is behaving View the status of your PureDrive connected home and battery View your household consumption and the power...

apps.apple.com

 

[Avendit]

Looks like this battery:

Home - Puredrive Energy

puredrive-energy.co.uk

At least the 5kw one they quoted me for.

Cheers for that. So.energy are saying that both 5 and 10kw are capped at 3kw discharge . Although reading the data sheet, I wonder what it means by rated output power 3000/5000VA?

Now just to decide whether to put a 10 panel NE facing set in or not :/ An extra 1700kwh/year generation for £2700, but it really alters the output curve to start generating much earlier in the AM.

 

[RedMod3]

And it looks like Puredrive app:

PureDrive

The PureDrive app enables owners of PureDrive batteries to monitor their homes’ energy on the go. With this app you can: Check how much charge your battery has and how it is behaving View the status of your PureDrive connected home and battery View your household consumption and the power...

apps.apple.com

I approached Puredrive on 18 November 2021 for further details, and as they never bothered to reply to my webform enquiry, I decided I would not bother with them.