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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
Yes it's likely to be correct assuming they are 380 to 400w panels giving you a 3.8 to 4kW array.
One inverter should be fine, it might be a 3.6kW or 5kW one ( likely to be 3.6kW)
The reason for two inverters, like my order, ( besides 18 panels and 7.2kW) is to take advantage of 4 hour window charging each battery fully, one inverter of the Givenergy type wouldn't achieve this on that 4 hours as max charge rate is 3.6kW.
Also, having two inverters in my scenario enables the house to be supplied with a max demand of 7.2kW if needed.
Does anyone on the Tesla energy plan know if/how strictly they enforce the 9 kWp solar array per powerwall requirement? I’m due to get a 9.6 kWp array and 1 powerwall installed, but I want to be on TEP so if it’s a hard requirement I will need to scale back the solar to <= 9 kWp. I’ve emailed octopus to check but currently awaiting a reply.
WannabeOwner
Well-Known Member
I reckon I'm going to go down that route too.
(I have high background usage due to computer servers)
Had 16 South-facing panels and 2x PowerWall. Charged PowerWalls overnight on E7 ... Solar never exceeded household use - or not by much, and some PowerWall discharge had occurred before sun came up so there was a bit of room to store any excess PV during the day.
Added a further 32 ESE panels. My back of envelop maths was that this would not be enough ... Only had them 10 days and not had a blue-sky day yet but looks like it is peaking at 3.5kW (does that sound right?)
... they were commissioned the day before I went on holiday, and I had not read the Zappi manual to figure out how to consume any excess into the EV. So whilst away I watched it merrily exporting to the grid for most of the day ...
I tried to change Cheap Rate to be only an hour to minimise the level that the PowerWall charged to (not knowing of a different way to limit that). Turns out then when sunny the 48 panels will charge the 2x PowerWall from 20% reserve to full in 2 hours! so any overnight charge can't be used-up before the sun is recharging the battery ...
Although I think there is something wrong (or I am misunderstanding??) but the APP often shows the house using 0kW - i.e. whatever the PV is generating is shown as going into battery, or export to grid. The graph for HOUSE shows 0kW for several hours at a time (probably at the same time that it shows EXPORT happening). This is definitely not possible, the servers definitely didn't stop ... and I never saw 0kW for the house before the new panels were added.
So then I changed the setting to SELF POWERED. Its been like that for a week (dunno if that is enough for AI?) and it hasn't charged at all overnight. We've had 2 or 3 back-to-back overcast days, and it has only charged to top up back to 20% Reserve overnight (i.e. typically "nothing"). On sunny days 2x PowerWall has been fully charged in 2 hours ... and then the rest exported.
So clearly my back-of-envelope was wrong (or something is amiss with CONFIG). I'm not sure I can reliably stuff the excess into EV (some days yes, but not every day if we haven't been anywhere for a few days)
I'm happy to do some programming to have a go with API to try to get better control. If I can reasonably predict sunshine-hours from a forecast (I'll assume that, until I find I can't, and then compromise on whatever I can actually attempt) then I will charge PowerWall to a percentage that will, approximately, get PowerWall charged to 100% during the day and then run that down after sunset / overnight.
Your setup sound similar to mine; 2 sets of panel, 2 Powerwalls & Zappi.
0W home use is rare. Something not right.
self-powered will not charge the Powerwalls at all unless the reserve is breached. If it is, the grid will charge them and power the house until the reserve is topped up.
assuming the 32 panels are 300W, I’d expect a peak around 8-9kWh on a sunny day. In light cloud, 3.5 is probably right
Which app are you reading? Tesla?
maybe there is a CT clamp in the wrong place
0W home use is rare. Something not right.
self-powered will not charge the Powerwalls at all unless the reserve is breached. If it is, the grid will charge them and power the house until the reserve is topped up.
assuming the 32 panels are 300W, I’d expect a peak around 8-9kWh on a sunny day. In light cloud, 3.5 is probably right
Which app are you reading? Tesla?
maybe there is a CT clamp in the wrong place
even ‘only’ 3.5kw is 28kwh generated over an 8 hour period. And you‘ll likely get a lot more in summer. What are you designing for? Trying to have enough spring/summer solar to cover your usage and putting it into the battery? Trying to oversize to have enough solar over winter?
48 solar panels is a pretty huge array
48 solar panels is a pretty huge array
PITA
Model 3 Performance
This doesn't sound right... as @Dilly suggests, a CT Clamp sounds 'missing' or not in the right place.
Your house should never show '0kW' unless everything is turned off... and this maybe why the Tesla AI isn't charging your batteries... because there isn't any use showing. But also remember 'Self-powered' mode doesn't use the Tesla Ai... it just uses battery power down to your 'reserve for backup' level. You need 'Time Based Control' for the Ai to manage your charging intelligence.
If Solar production is less than 1.4kW ... then the Zappi won't use it to charge the car... the excess has to be / or above 1.4kW otherwise it'll just export it to the Grid. The 1.4kW is an industry wide charging minimum standard for Ev's.
WannabeOwner
Well-Known Member
Yes. Is there anything else available? (I've not looked, but I use TesalFi for driving ... an equivalent API gadget that saved me having to write, and debug!, one for PowerWall would be good.)
Its intermittent though, does that still sound like CT Clamp error? Tesla APP will report house as 0kW for a period (an hour or two maybe) and then a level that seems reasonable. Happy to get the installer to sort it out, but any thoughts would be appreciated.
I was thinking of having enough for shoulder months, and that any excess in Summer could be dumped into car. But I reckon my capacity-needed maths might have been pessimistic (or the dodgy APP output isn't matching reality, and once that is fixed things will even out ... but the PowerWalls go from 20% to full in 2 hours (even if the APP says the house is using 0% it isn't, so I presume that PowerWall Charging is from "spare juice").
Looks like I'm definitely going to have to plan for significant dump-to-car on sunny days. Or take up Aluminium smelting!
Ah, OK, thanks. I did use that initially, maybe not for enough days for AI to learn to compensate? it didn't moderate from just filling the PowerWall to 100% overnight
I'll drop the Reserve from 20% to 10% ... which was where I had it before. Most of our powercuts are a couple of seconds, and if I get a scheduled powercut I can deliberately increase the reserve to 100%
I don’t know if it still is the case but the AI used to only store a couple of days.
my questions would be: is your Tesla app showing all your solar and when there is none, is the PW discharge equal to home consumption?
equally, does your Zappi see similar figures?
There may be slight discrepancies but generally should be the same.
When your second set of panels were installed, was the Zappi solar CT clamped round the the new solar live feed (in addition to the existing) in your consumer unit?
in addition to the Myenergi & Tesla apps, I have Geo Solo II displays for live data both set of panels (see photo) alongside my smart meter display.
the photo shows that 4.7 is being exported, the main panels are generating 5 and the secondaries have shut down (they can’t export)
WannabeOwner
Well-Known Member
Thanks.
Good question. There are 2x brown, 2x blue into a junction box, and two cable clamps on the Browns, but the original solar is down the far end of the house, so might not be wired-in (I'm guessing) and the new is two "systems" (2x inverters maybe? not something I'm technical on).
Installer is coming back to have a look (but due to holiday not until end of month), so until them I'm happy to experiment, provide him with info so he comes with the necessary bits / solution, and happy with any available work-around until then - e.g. manually start a car charge connected to Zappi to do my best to divert excess into a car instead of export to grid.
I think the graphs may actually have some indication of the problem
Yesterday had good sun; export shows as between 08:30 and 15:00.
On the GRID Graph a spot reading (of a maximum export) shows -3.2kW whereas the scale indicates a max of -11.9kW. I wonder if the -3.2kW is the house usage (2-3kW trough/peak would be about right) and the rest as export? The positive max is 5.3kW which matches the scale (although plenty of white space above ... so not 100% sure about that one either)
Overnight peak usage is immersion (Solar thermal awaiting maintenance
), earlier part of overnight is my normal background usage (SPOT checks show 1.7kW - 2.1kW)The HOME graph shows nothing from 06:00 onwards (battery charges 06:40 maxes out at 08:25 and then GRID shows export starting at 08:30 and stepping up at 09:35 when battery gets to 100%). Instant reading of an overnight peak shows 5.2kW which matches the scale
Solar ramps up from 07:25. So no idea what the house was running on from 06:00 when HOME was showing 0kW, and battery charging.
If I click for an instant reading (on SOLAR graph) I get a peak of 3.5kW (which, unlike GRID and BATTERY, matches the scale). We had some good sunshine yesterday, with some wandering clouds, so I should have been getting full belt for 48 panels ... on the face of it I'm generating 3.5kW from PV and exporting 11.9 kW !
The Battery charge ramps from 06:40 and maxes at 08:25, and then finishes (100% charge) at 09:35. Discharge proper (ignoring some for clouds passing over) starts at 17:15. Solar drops to "low" at 16:20 and zero at 19:00. Battery discharge does seem to ramp up 17:15 to 19:00, and then steady (ignoring peaks) after that, which appears to match the solar falling off.
I tried manually using the Zappi at about 14:44 ... but it stopped after a couple of minutes
Not sure what, if anything, that indicates.
Zappi says it all. Something not right with the solar CT attached to it. There shouldn’t be a warning triangle. it’s not serious.
you can go into settings and check whether one of the clamps is indeed set to solar, particularly as you have some clamps in place
my three pic’s below, taken just now, show the kind of thing your Zappi should be displaying which should roughly match the Tesla app albeit that May be wrong too!
My Eddi diverter is using the other 3KWh to heat water
you can go into settings and check whether one of the clamps is indeed set to solar, particularly as you have some clamps in place
my three pic’s below, taken just now, show the kind of thing your Zappi should be displaying which should roughly match the Tesla app albeit that May be wrong too!
My Eddi diverter is using the other 3KWh to heat water
Run the calcs off pvwatt as described back around page 20-30 of the thread and see what you think. I'm Edinburgh with a 14 panel SW facing array proposed, and 8 NE facing. Peak generation is actually around 4kw, but will happen less than 30 hours a year. So I'm happy with a smaller inverter if I can persuade them.
Weirdly I couldn't persuade them NOT to apply to the dno, but it may be because I need a duel string inverter so they do need to know to limit it or not.
RedMod3
Member
Today was a good day while I was out, we imported 20kWh at 5p overnight, fully charged our single Powerwall and our solar diverter completely topped up our hot water tank. If only our 2nd Powerwall was in, we could have avoided giving the grid 3kW of power worth 15p.
Attachments
PITA
Model 3 Performance
When you get two Powerwalls your charts will look like this
Just brutal downloading for 4 hours, then cut the Grid Off completely
Octopus Smash & Grab Tariff
While my Powerwalls and 7kw Ev Charger is going through the front door, seen in the charts below.
My 3 Phase 11kW charger is kicking the back door in as well, at the same time.
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PITA
Model 3 Performance
... and every minute filled with smugness...Only a 383.5 year pay back
What's the ROI on Priceless
