Circular reasoning (Rolfe's solar energy system)

[Rolfe]

Well, I finally got the export tariff, a week ago while I was on holiday. Now I have to re-learn everything to favour use of 7p overnight electricity and so export as much as I can at 15p. So far so good, with my first day home from holiday netting 38.4 kWh, probably a bit more than I put in the car's battery on a scheduled charge the previous night. This week is showing as £4.06 imported and £10.39 exported so far, even though there was one day that didn't even manage to export 5 kWh because the weather was so foul. (Then almost wall to wall sunshine the next day!) Even allowing for the standing charge I'm in profit already.

I have one query I hope someone will answer. When I got home I set a scheduled charge in Octopus, but then I didn't dare plug in because it was still mid-afternoon and I didn't know how to stop the car taking the solar excess (which I now want to export) rather than waiting for the schedule. I solved this by waiting till it was almost twilight before going back out and plugging the car in. It worked perfectly and I woke to a car on 100% with evidence of it having balanced.

But this seems a bit of a pain. Is there some way to get the Zappi NOT to take the sunshine, but still to charge when the Octopus schedule kicks in? Would setting the charger on Stop work?

 

[johnb80]

Well, I finally got the export tariff, a week ago while I was on holiday. Now I have to re-learn everything to favour use of 7p overnight electricity and so export as much as I can at 15p. So far so good, with my first day home from holiday netting 38.4 kwh, probably a bit more than I put in the car's battery on a scheduled charge the previous night. This week is showing as £4.06 imported and £10.39 exported so far, even though there was one day that didn't even manage to export 5 kw because the weather was so foul. (Then almost wall to wall sunshine the next day!) Even allowing for the standing charge I'm in profit already.

I have one query I hope someone will answer. When I got home I set a scheduled charge in Octopus, but then I didn't dare plug in because it was still mid-afternoon and I didn't know how to stop the car taking the solar excess (which I now want to export) rather than waiting for the schedule. I solved this by waiting till it was almost twilight before going back out and plugging the car in. It worked perfectly and I woke to a car on 100% with evidence of it having balanced.

But this seems a bit of a pain. Is there some way to get the Zappi NOT to take the sunshine, but still to charge when the Octopus schedule kicks in? Would setting the charger on Stop work?

Set the charger to Stop and then when the solar PV has stopped change to ECO+. Switch off smart charging in the Octopus app and set a schedule 23:30 to 05:30 in the zappi. at least once per month do a smart charge to adhere to Octopus T&C's

 

[Rolfe]

OK, I can see how that works to save going back out and physically plugging the car in. Useful, thanks. I don't see the benefit of turning off smart charging though. In fact when I set the smart charge to add 70% by 9am (the car was on 39% and I wanted it to have time to balance) I was allocated 11.30 till 5.30 anyway, and it worked fine.

 

[Rolfe]

It's all going pretty well. I set the house battery to charge from 11.31pm to 5.29am. It's usually back to 100% within about 40 minutes, from wherever it fell to by powering the house after the sun set. That time will lengthen as the days shorten of course. It only went down to 90% yesterday evening, as I hadn't run the fan heater. So within that time I ran the dishwasher and set the Eddi to heat from 4.30am till 5.30am, but it only takes about 40 minutes to get to temperature. The battery wasn't drained at all because it was still on charge,

That lot used 4.6 kwh, excluding the half-hour before midnight when the battery was recharging (abother 1 kwh I would estimate), but including the overnight base load of the house. So 32.2p altogether. The weather has been dull and showery today and so far the solar has only managed 9 kwh. However, that is still £1.35 and it has a way to go yet. Even adding in the standing charge of 61.25p I'm still ahead of the game, and I repeat this is a horrible day.

It will be interesting to see how things change as the days shorten, and then I have to run the central heating boiler and more lights during the day. I certainly won't be in profit, but I should be able to do it all at 7p/unit thanks to the battery. Most people seem to think that 9.5 kwh is plenty for a house this size to avoid having to use power at peak time rates, but to do that I need to step up my phasing out of the incandescent light bulbs. Which I should probably have done long ago, but I stockpiled more than I needed at the time when they were going off sale and the low energy bulbs available were rubbish (and my mother, who had glaucoma, couldn't see by them).

Hopefully I'll have everything set up the way I like it, and can simply carry on as normal without thinking about it too much. Once I have a feel for how it's going in the darker days I'll know better. I just have to remember to turn the Eddi on after sunset and back off when I wake up, to prevent it taking solar to keep the water scalding hot all day, which isn't needed. And to turn on the Zappi after sunset on the days I need to charge the car.

MyEnergi need to incorporate a switch to set its products to either use or not use solar excess, as required. They seem to assume that if you have solar, you'll want to use it. They don't seem to have figured out about the price differential between export and overnight cheap rates.

 

[johnb80]

OK, I can see how that works to save going back out and physically plugging the car in. Useful, thanks. I don't see the benefit of turning off smart charging though. In fact when I set the smart charge to add 70% by 9am (the car was on 39% and I wanted it to have time to balance) I was allocated 11.30 till 5.30 anyway, and it worked fine.

But sometimes it will start to charge at 22:00 or even earlier, in your case sucking energy out of the batteries, thats why I said switch off smart charging.

 

[Rolfe]

It won't do that without telling me, though. If I do get a time outwith the window where the battery is set to charge then I can always do something then. Either reject the smart charge and do as you say, or set the battery to charge at the same time as the smart charge window.

I see it can be done either way, really. I note that when I asked for 70% earlier in the week, which does need six hours, I was actually given 11.30 till 5.30. I checked precisely for that reason. I don't mind doing it Octopus's way most of the time, I'm getting a good deal from them. And obviously if I come back needing more than 70% I'll either have to do it over two nights by your method, or ask Octopus for a scheduled charge then deal with the battery issue separately.

It's obviously pretty flexible, and I'm interested to see as the time goes on what slots are actually allocated. I can always reject them if I don't like what I'm offered.

 

[johnb80]

It won't do that without telling me, though. If I do get a time outwith the window where the battery is set to charge then I can always do something then. Either reject the smart charge and do as you say, or set the battery to charge at the same time as the smart charge window.

I see it can be done either way, really. I note that when I asked for 70% earlier in the week, which does need six hours, I was actually given 11.30 till 5.30. I checked precisely for that reason. I don't mind doing it Octopus's way most of the time, I'm getting a good deal from them. And obviously if I come back needing more than 70% I'll either have to do it over two nights by your method, or ask Octopus for a scheduled charge then deal with the battery issue separately.

It's obviously pretty flexible, and I'm interested to see as the time goes on what slots are actually allocated. I can always reject them if I don't like what I'm offered.

No problem, you run how you wish, I only highlighted a potential issue thats all.

 

[Rolfe]

Yes, it's very sensible to take everything into account. I can't see much difference whichever way I do it, unless I want more than 70% in a session when I'll have to get a schedule or pay over the odds. And actually that's unlikely, because if I ever come home below 30% I'm probably not going to need the full range again the next day.

In general I'm thinking, I won't always need to dive in and start the charge at 11.30, and if Octopus would rather spare the surge on the grid at that time I'm happy to let them. Although today I did accidentally get a schedule to add 70% because I hadn't changed the settings, and again I got 11.30 till 5.30 (although split up into consecutive sessions).

 

[Caramaddy]

This was a marathon Of a thread to read (not all of it!) but very interesting indeed. Sadly it has raised more questions than answers in my head!
To be fair I did not understand all that was being discussed. Rolfe’s position regarding export not being paid was unique and well done for sorting it to your satisfaction. When I get my head around it, I may come back and ask some stupid questions!

Thank you all contributors!

 

[Bam Bam]

This was a marathon Of a thread to read (not all of it!) but very interesting indeed. Sadly it has raised more questions than answers in my head!
To be fair I did not understand all that was being discussed. Rolfe’s position regarding export not being paid was unique and well done for sorting it to your satisfaction. When I get my head around it, I may come back and ask some stupid questions!

Thank you all contributors!

Glad it was helpful. There are probably You Tube videos that explain it all more succinctly!

Just to say, Rolfe's non-export period isn't unique, but rather a period you go through before your export is approved.

It took several weeks for us as well. Once it is done its done though and you can get export credit from then on.

 

[Rolfe]

I was just chatting to a neighbour across the road while he was cleaning his car (I'd just finished doing mine) and now that's the second person on my list to talk out of a plug-in hybrid. "Oh I couldn't be doing with all this stopping on 1,000 mile trips!" I asked how often he does 1,000 mile trips. Not often, apparently. Then I pointed out that nobody is going to be driving 1,000 miles in a day and maybe 500 miles was more realistic. Then I gave him an earful about how easy it was, including the info that I'm off to Brighton again the day after tomorrow (450 miles) without a care in the world and I'll be ready to eat the steering wheel by the time I have to make my first stop.

I hope he thinks about it. Given that he could charge at home just as easily as I can, a plug-in hybrid seems absolutely senseless.

 

[Archev]

I was just chatting to a neighbour across the road while he was cleaning his car (I'd just finished doing mine) and now that's the second person on my list to talk out of a plug-in hybrid. "Oh I couldn't be doing with all this stopping on 1,000 mile trips!" I asked how often he does 1,000 mile trips. Not often, apparently. Then I pointed out that nobody is going to be driving 1,000 miles in a day and maybe 500 miles was more realistic. Then I gave him an earful about how easy it was, including the info that I'm off to Brighton again the day after tomorrow (450 miles) without a care in the world and I'll be ready to eat the steering wheel by the time I have to make my first stop.

I hope he thinks about it. Given that he could charge at home just as easily as I can, a plug-in hybrid seems absolutely senseless.

Have a safe trip. I agree, I can’t see the point of a hybrid with or without the plug in. Brother in law has a new Renault and the sales folk fed him a tale about never having to waste time plugging in ?? Words failed me ??

 

[Caramaddy]

I have a Lexus Hybrid. The Lexus EV range is poor compared to other makes. The Toyota BZ4e was tempting but too expensive at the time. The MG has definitely changed by perception of EV’s. I agree a full EV is the way to go provided it is the car you require and it is in your price range.
MG used is an excellent way to dip your toe into the warm water of EV ownership.

 

[Rolfe]

I've just had an email correspondence with a friend who mentioned on an online group that she was going to test-drive a plug-in hybrid. I've persuaded her to re-think about a full EV, which is encouraging. I'm wondering if I should print out the correspondence and stick it through Mr Fordyce's letter-box.

 

[Archev]

I've just had an email correspondence with a friend who mentioned on an online group that she was going to test-drive a plug-in hybrid. I've persuaded her to re-think about a full EV, which is encouraging. I'm wondering if I should print out the correspondence and stick it through Mr Fordyce's letter-box.

Yeah any petrol or diesel engine is going to gas kids in prams / strollers or animals with their exhausts.

 

[Rolfe]

She's just emailed back saying she couldn't persuade her husband, who thinks "it's still too much of a leap in the dark". They were apparently shown an ex-demo Skoda Superb with only 800 miles on the clock at a great price, which ticked all the boxes as regards spec, and went for it. It does sound like a lovely car, as a car, but I think they're in for the worst of both worlds.

She says maybe she can persuade her husband next time. Oh well.

 

[Caramaddy]

Get a home charger , switch to octopus agile , get the home battery , add solar if you like . But get all the above that talk to home assistant so you can charge at the cheapest rates whenever they are

I am not sure if Burden is the correct post or someone else. They suggested getting batteries first with Octopus Go and use the night tariff to charge the batteries.

Is this possible? Sounds an interesting idea but how efficient would it be without solar?

Sorry if I have not understood the post.

Would my electricity supply be able to charge the car, charge the batteries AND run the washing machine, tumble dryer and dishwasher?

 

[Rolfe]

I think this is actually quite a good idea. Get a battery that's large enough and it should see you through the day till the next off-peak period so that all your usage is at off-peak prices. Solar is to some extent the icing on the cake - you end up trying to minimise your actual solar usage so that you can export as much as possible, anyway. It makes better sense that way because you're using off-peak electricity at 7p while exporting the solar at 15p. The solar panels become a profit generator more than they actually supply your house.

I asked about this earlier, how much can the domestic supply cope with all at once, and was assured that it was a lot. You are probably not going to be charging the car and the home battery and the washing machine and the tumble dryer and the dishwasher all at the same time after all.

You can always time the car charge to start a bit later to give you time to run an appliance or two in the off-peak window before the car starts. You can have a rota where you use only two or three of these five things at the same time. Someone else had the figures though, and can give more detail. I'm confident that if you just keep an eye on what you're doing you can run the house including lighting, powering a central heating boiler, cooking, vacuuming, power showers and so on (heating your water tank is another thing that can be shifted to off-peak time) from a battery.

The only other thing to watch out for is the battery's discharge power. I have to keep an eye on what I'm doing when I'm cooking so that I don't ask for too much at once to exceed the 3.5 kw capability of the battery. If I were to turn on the oven, the hob and the kettle at once, the system would draw from the grid because the battery can't cope with all that at once. But I'm learning how to stagger the turning on so that only one appliance is drawing full power at any one time. (Once the oven or the hob is up to temperature they don't draw a lot, and other things can be turned on.) If I do occasionally draw a little bit of peak-time power by accident it's transient and pennies anyway.

This was explained to me when I got my solar panels, that in fact house battery, EV charger and off-peak rates would in themselves generate a lot of saving, and why shell out for solar panels as well? My best reply was, have you seen my roof? It would be a crime not to! And they are now turning a profit. But they're the least essential part of the system and if for some reason your house isn't suitable for solar I think you should still go for it.

 

[Rolfe]

But sometimes it will start to charge at 22:00 or even earlier, in your case sucking energy out of the batteries, thats why I said switch off smart charging.

While faffing around this afternoon I accidentally got a charging schedule for 70%, and again I was allocated 11.30 to 5.30, split into about three slots but actually continuous. I have now re-jigged Octopus to get what I actually want, which is 30%, and have been allocated 2.30 to 5.00, again in three slots but continuous. If that's when Octopus wants me to charge then that's fine by me. It does look a bit as if they are trying to squeeze charging into the actual cheap-rate period anyway.

I don't actually need the car charged up till Tuesday morning, but I decided to go for it tonight as a safety measure. If for any reason it doesn't charge, I have tomorrow night to make damn sure it does it. (Either that or I'm on the 50 kw CPS charger at the end of my road, begging it to hurry up!)

I could actually do with a nice cheap-rate slot before 11.30, to fund my fan heater habit. Easy enough to look on the app and see when the slots are, and change the battery settings accordingly. But it's all one, I can just use what's in the battery for the heater then let it charge once the off-peak time kicks in, as usual.

 

[Rolfe]

More discoveries. Due to trains of thought mainly started by the discussion in the Free Energy thread, I decided to try a bit of battery export. I set the battery to export between 9pm and 10pm, reckoning that I can spare that easily even if I also want to run the fan heater.

Had a look at things about ten past nine, and the battery was discharging as instructed, but where was the power going? There was just a little blip of export, then everything seemed to be being sucked up by the house. Headscratching for a moment, then I realised that the Eddi, which I had already turned on to avoid the issue from yesterday when I forgot, had seen this as excess and was now heating the water. Damn. Turn Eddi off.

Gave it another ten minutes, had a look, and the same thing was happening. All the power going to the house. Double damn, the Zappi of course, also turned on so that the scheduled Octopus charge can kick in at 2.30 am. Once the Eddi was off, the Zappi saw excess and grabbed it. Stopped the Zappi. (Which of course canned the Octopus scheduled charge. Don't know if I'll get the same time slots when I set the Zappi back on. Complications upon complications. Learning curve.)

NOW we are motoring, exporting 3.5 kw to the grid. It's taking a bit of getting used to, seeing grid export as a positive thing rather than money down the drain... Three months of learning to use the system one way, and now I'm having to reverse all my assumptions. I don't need the battery to last until sunrise. This is much better.

I'll see how things are at ten, and if I want to do some more, and how using the fan heater will affect it. I also don't know what happens if I set the bottom of the timed export to higher than 4%, the reserve capacity of the battery. Will that stop the battery discharging entirely, thus forcing the house to draw from the grid, or will it simply stop the export and allow the remaining battery charge to go on powering the house? I would surmise the latter.