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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
I think you need to look at the fact that they probably make money even when you’re paying 7.5p.
Even though it’s winter now you’ll still see the 30 min agile prices dip below 7.5p during the cheap periods.
Even though it’s winter now you’ll still see the 30 min agile prices dip below 7.5p during the cheap periods.
WannabeOwner
Well-Known Member
Just thinking out loud:
Could you (some how ...) change the PowerWall to 100% to stop it discharging during one of those periods? (and that would also mean it would Charge, if lower than that ... although (if not part of the PowerWall Timer Schedule) only at 3.5kW (i think) rather than 10kW (unless the API has improved to allow controlling that)
It’s all very new to me but I guess I could change the Backup Reserve setting to 100%. That would still allow it to charge but I think would not discharge.
The only downside I can see is that between the end of the IO off peak schedule and the point I’m awake to change the reserve setting, the house would draw from the grid at peak rate, although this would be fairly minor usage at that time of the day. I’m sure there would be a way to automate it with Home Assistant but I’ve only just started messing around with that so need to research.
ACarneiro
Active Member
Yes, you have stumbled across the one snag of the IO/Powerwall combo.
It’s not that usual to get charging slots outside the 23:30 to 05:30 hours but it does happen sometimes.
The way I usually deal with it is to check the charging slots just before going to sleep (they can change sometimes) and adjust the peak/off peak tariffs on the Powerwall accordingly.
PITA
Model 3 Performance
Exactly how we do it.
We have two 22kW fast chargers wired into a seperate 3 Phase Consumer Unit which are nowhere near the Powerwalls.
This means we can charge both cars at anytime, directly from the Grid.
The Powerwalls and Gateway do their own thing, supplying the house and are completely unaffected.
Works perfect for Intelligent Octopus setup.
We then have a third 7kW charger wired into the Tesla Gateway (on Grid-Tied side)... as a backup to charge from Solar during Summer. Should we choose to do it that way.
We then also have a 32amp 7kW Commando Socket wired into Tesla Gateway (on backup side) for emergency use, or charging from the batteries during a Grid Blackout using the Tesla Universal Mobile Charger.
All three chargers talk to each other and load balance if necessary.
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I dont know if it depends on the area but over here I get slots for most of the day. Adding slots to the app is one way to deal with it BUT you must remember to remove or adjust for the next day. Setting the backup to 100% does the same BUT you must remember or set an alarm to put it back down for when the slot ends.... It's a pain in the BUT.
In the end I just had it rewired so the gateway does not see the chargers (the way it should of been done from the start as I was aware of this but thats another story) and now I only set the backup to 100% with an alarm as to topup the battery, for the most part when the weather is nasty in fear of grid failure. Much easier to live this way imho.
ACarneiro
Active Member
Oh, that’s really interesting.
I very rarely get slots during the day over here. And when I do it tends to be within around an hour either side of Off Peak times.
Must surely be something to do with the energy mix in different regions…
ACarneiro
Active Member
That’s an option, but I have 4 Powerwalls, so they can charge at a rate of 20kW from the grid (they usually stick to around 14, but they definitely have the capability of going higher).
Between them, immersion heater, heat pumps and appliances, my available 100A really needs to be managed.
The benefit of the gateway seeing the load of the car charging is that
- you can charge your car during a power cut (although why would you?)
- the Gateway can modulate the Powerwall charge rates so that the combined import to the house never goes above 22kW (value set by me) so there is no risk of blowing a mains fuse.
The second one is A Big Deal for me so I’m keeping the setup as it is
PITA
Model 3 Performance
The reason I had the Commando Socket fitted to the Backup Side... is a scenario during Summer if we had a localised Grid blackout.
The Gateway would isolate our house... and the Solar Array would shut down if batteries were full... which they will be next year, as we'll be exporting it all for cash.
In this scenario, we could still dump our excess from the batteries into the car, via the Commando Socket and keep the solar array operational.
Better than have the system shut down the Solar Array...
Also... when the Zombies come...
ACarneiro
Active Member
I was surprised to find the Powerwall had only charged to 70% last night. From some research I now understand it learns usage patterns and uses weather forecasts to determine optimal charging. It’s likely due to a decent weather forecast for today so hopefully it will mostly top up throughout the day.
I’ve read about people using home assistant to automatically change the backup reserve overnight to force a charge to 100% and then change the reserve again in the morning to something low (0% - 5%) so they can get the full use throughout the day. Is this likely to cause early degradation of the battery? Or is it better to let the AI do it’s thing but risk it sometimes getting it wrong and not charging the battery enough for a days use?
I’ve read about people using home assistant to automatically change the backup reserve overnight to force a charge to 100% and then change the reserve again in the morning to something low (0% - 5%) so they can get the full use throughout the day. Is this likely to cause early degradation of the battery? Or is it better to let the AI do it’s thing but risk it sometimes getting it wrong and not charging the battery enough for a days use?
Strangely mine only charged to 88% last night and it shouldn't be relying on the sun since ive got it set to export all the solar.
Since yours is not set for export yet it would of course make sense to store any extra solar yourself.
What was your state of charge by the time it started charging from the grid last night?
WannabeOwner
Well-Known Member
I take an "assume not" view - Battery intended to be charged and discharged, fully-ish, at least one cycle every day.
Well ... that depends how much you pay for Peak tariff. There was some chatter on here a while back that even a short period of Peak Tariff - e.g. if the guestimate of Sun for the day is too ambitious - negates all the saving if you run out - or even if you fail to get to 100% during the day, and it was better to Export some (particularly if the Export rate is more than Tuppence), rather than run out. Also, this time of the year, there is a lengthy interval between end of Off Peak and Solar generation exceeding house usage (more so if PV is South facing (than East), a lot more if it is West facing
I think it depends a bit if you can charge a car. This time of the year I rarely get more than 3 or 4 kWh of export ... the car pretty much always has room for that ... and Tesla's charging estimate of "tomorrows sunshine" has no account for what my car can take NOR whether I am about to go somewhere. So forcing the charge to 100% is fine, in my view, if you can dump any Export into Car ... or even to Export it.
I’ve been playing around with different reserves and had that set to 5% last night which is the level it was at when it started charging in the off peak window.
The solar produced 2kW yesterday even with a fair amount of rain so with todays forecast of sun and no cloud all day it’s got a good chance of topping the battery off by the time we all get home.
Until I get my export MPAN I really want to use all the solar I can and export none ideally. So letting the AI leave some spare capacity in the battery for the expected solar generation was a good move today.
The car is rarely at home during weekdays so I wouldn’t usually be able to utilise any excess solar generation on that.
When I can get paid for export (more than its costs to import) I can see it makes sense to fill the battery overnight and export every last drop of solar.
